Release Notes¶

Version History¶

This table tracks the meta-package versions and the version of each Qiskit element installed:

Table 1 **Version History**¶
Qiskit Metapackage Version	qiskit-terra	qiskit-aer	qiskit-ignis	qiskit-ibmq-provider	qiskit-aqua

Note

For the 0.7.0, 0.7.1, and 0.7.2 meta-package releases the versioning_strategy policy was not formalized yet.

Notable Changes¶

Qiskit 0.25.0¶

This release officially deprecates the Qiskit Aqua project. Accordingly, in a future release the qiskit-aqua package will be removed from the Qiskit metapackage, which means in that future release pip install qiskit will no longer include qiskit-aqua. The application modules that are provided by qiskit-aqua have been split into several new packages: qiskit-optimization, qiskit-nature, qiskit-machine-learning, and qiskit-finance. These packages can be installed by themselves (via the standard pip install command, e.g. pip install qiskit-nature) or with the rest of the Qiskit metapackage as optional extras (e.g. pip install 'qiskit[finance,optimization]' or pip install 'qiskit[all]' The core algorithms and the operator flow now exist as part of qiskit-terra at qiskit.algorithms and qiskit.opflow. Depending on your existing usage of Aqua you should either use the application packages or the new modules in Qiskit Terra. For more details on how to migrate from Qiskit Aqua you can refer to the Qiskit Aqua Migration Guide.

Terra 0.17.0¶

Prelude¶

The Qiskit Terra 0.17.0 includes many new features and bug fixes. The major new feature for this release is the introduction of the qiskit.algorithms and qiskit.opflow modules which were migrated and adapted from the qiskit.aqua project.

New Features¶

The qiskit.pulse.call() function can now take a Parameter object along with a parameterized subroutine. This enables assigning different values to the Parameter objects for each subroutine call.

For example,

from qiskit.circuit import Parameter
from qiskit import pulse

amp = Parameter('amp')

with pulse.build() as subroutine:
    pulse.play(pulse.Gaussian(160, amp, 40), DriveChannel(0))

with pulse.build() as main_prog:
    pulse.call(subroutine, amp=0.1)
    pulse.call(subroutine, amp=0.3)

The qiskit.providers.models.QasmBackendConfiguration has a new field processor_type which can optionally be used to provide information about a backend’s processor in the form: {"family": <str>, "revision": <str>, segment: <str>}. For example: {"family": "Canary", "revision": "1.0", segment: "A"}.

The qiskit.pulse.Schedule, qiskit.pulse.Instruction, and qiskit.pulse.Channel classes now have a parameter property which will return any Parameter objects used in the object and a is_parameterized() method which will return True if any parameters are used in the object.

For example:

from qiskit.circuit import Parameter
from qiskit import pulse

shift = Parameter('alpha')

schedule = pulse.Schedule()
schedule += pulse.SetFrequency(shift, pulse.DriveChannel(0))

assert schedule.is_parameterized() == True
print(schedule.parameters)

{Parameter(alpha)}

Added a PiecewiseChebyshev to the qiskit.circuit.library for implementing a piecewise Chebyshev approximation of an input function. For a given function \(f(x)\) and degree \(d\), this class class implements a piecewise polynomial Chebyshev approximation on \(n\) qubits to \(f(x)\) on the given intervals. All the polynomials in the approximation are of degree \(d\).

For example:

import numpy as np
from qiskit import QuantumCircuit
from qiskit.circuit.library.arithmetic.piecewise_chebyshev import PiecewiseChebyshev
f_x, degree, breakpoints, num_state_qubits = lambda x: np.arcsin(1 / x), 2, [2, 4], 2
pw_approximation = PiecewiseChebyshev(f_x, degree, breakpoints, num_state_qubits)
pw_approximation._build()
qc = QuantumCircuit(pw_approximation.num_qubits)
qc.h(list(range(num_state_qubits)))
qc.append(pw_approximation.to_instruction(), qc.qubits)
qc.draw(output='mpl')

The BackendProperties class now has a readout_length() method, which returns the readout length [sec] of the given qubit.
A new class, ScheduleBlock, has been added to the qiskit.pulse module. This class provides a new representation of a pulse program. This representation is best suited for the pulse builder syntax and is based on relative instruction ordering.

This representation takes alignment_context instead of specifying starting time t0 for each instruction. The start time of instruction is implicitly allocated with the specified transformation and relative position of instructions.

The ScheduleBlock allows for lazy instruction scheduling, meaning we can assign arbitrary parameters to the duration of instructions.

For example:
```
from qiskit.pulse import ScheduleBlock, DriveChannel, Gaussian
from qiskit.pulse.instructions import Play, Call
from qiskit.pulse.transforms import AlignRight
from qiskit.circuit import Parameter

dur = Parameter('rabi_duration')

block = ScheduleBlock(alignment_context=AlignRight())
block += Play(Gaussian(dur, 0.1, dur/4), DriveChannel(0))
block += Call(measure_sched)  # subroutine defined elsewhere
```
this code defines an experiment scanning a Gaussian pulse’s duration followed by a measurement measure_sched, i.e. a Rabi experiment. You can reuse the block object for every scanned duration by assigning a target duration value.
Added a new function array_to_latex() to the qiskit.visualization module that can be used to represent and visualize vectors and matrices with LaTeX.
from qiskit.visualization import array_to_latex from numpy import sqrt, exp, pi mat = [[0, exp(pi*.75j)], [1/sqrt(8), 0.875]] array_to_latex(mat)
\[\begin{split}\begin{bmatrix} 0 & \tfrac{1}{\sqrt{2}}(-1 + i) \\ \tfrac{1}{\sqrt{8}} & \tfrac{7}{8} \\ \end{bmatrix} \end{split}\]
The Statevector and DensityMatrix classes now have draw() methods which allow objects to be drawn as either text matrices, IPython Latex objects, Latex source, Q-spheres, Bloch spheres and Hinton plots. By default the output type is the equivalent output from __repr__ but this default can be changed in a user config file by setting the state_drawer option. For example:
from qiskit.quantum_info import DensityMatrix dm = DensityMatrix.from_label('r0') dm.draw('latex')
\[\begin{split}\begin{bmatrix} \tfrac{1}{2} & 0 & -\tfrac{1}{2}i & 0 \\ 0 & 0 & 0 & 0 \\ \tfrac{1}{2}i & 0 & \tfrac{1}{2} & 0 \\ 0 & 0 & 0 & 0 \\ \end{bmatrix} \end{split}\]
from qiskit.quantum_info import Statevector sv = Statevector.from_label('+r') sv.draw('qsphere')
Additionally, the draw() method is now used for the ipython display of these classes, so if you change the default output type in a user config file then when a Statevector or a DensityMatrix object are displayed in a jupyter notebook that output type will be used for the object.
Pulse qiskit.pulse.Instruction objects and parametric pulse objects (eg Gaussian now support using Parameter and ParameterExpression objects for the duration parameter. For example:
```
from qiskit.circuit import Parameter
from qiskit.pulse import Gaussian

dur = Parameter('x_pulse_duration')
double_dur = dur * 2
rx_pulse = Gaussian(dur, 0.1, dur/4)
double_rx_pulse = Gaussian(double_dir, 0.1, dur/4)
```
Note that while we can create an instruction with a parameterized duration adding an instruction with unbound parameter duration to a schedule is supported only by the newly introduced representation ScheduleBlock. See the known issues release notes section for more details.

The run() method for the QasmSimulatorPy, StatevectorSimulatorPy, and UnitarySimulatorPy backends now takes a QuantumCircuit (or a list of QuantumCircuit objects) as its input. The previous QasmQobj object is still supported for now, but will be deprecated in a future release.

For an example of how to use this see:

from qiskit import transpile, QuantumCircuit

from qiskit.providers.basicaer import BasicAer

backend = BasicAer.get_backend('qasm_simulator')

circuit = QuantumCircuit(2)
circuit.h(0)
circuit.cx(0, 1)
circuit.measure_all()

tqc = transpile(circuit, backend)
result = backend.run(tqc, shots=4096).result()

The CommutativeCancellation transpiler pass has a new optional kwarg on the constructor basis_gates, which takes the a list of the names of basis gates for the target backend. When specified the pass will only use gates in the basis_gates kwarg. Previously, the pass would automatically replace consecutive gates which commute with ZGate with the U1Gate unconditionally. The basis_gates kwarg enables you to specify which z-rotation gates are present in the target basis to avoid this.
The constructors of the Bit class and subclasses, Qubit, Clbit, and AncillaQubit, have been updated such that their two parameters, register and index are now optional. This enables the creation of bit objects that are independent of a register.

A new class, BooleanExpression, has been added to the qiskit.circuit.classicalfunction module. This class allows for creating an oracle from a Python boolean expression. For example:

from qiskit.circuit import BooleanExpression, QuantumCircuit

expression = BooleanExpression('~x & (y | z)')
circuit = QuantumCircuit(4)
circuit.append(expression, [0, 1, 2, 3])
circuit.draw('mpl')

circuit.decompose().draw('mpl')

The BooleanExpression also includes a method, from_dimacs_file(), which allows loading formulas described in the DIMACS-CNF format. For example:

from qiskit.circuit import BooleanExpression, QuantumCircuit

boolean_exp = BooleanExpression.from_dimacs_file("simple_v3_c2.cnf")
circuit = QuantumCircuit(boolean_exp.num_qubits)
circuit.append(boolean_exp, range(boolean_exp.num_qubits))
circuit.draw('text')

     ┌───────────────────┐
q_0: ┤0                  ├
     │                   │
q_1: ┤1                  ├
     │  SIMPLE_V3_C2.CNF │
q_2: ┤2                  ├
     │                   │
q_3: ┤3                  ├
     └───────────────────┘

circuit.decompose().draw('text')

q_0: ──o────o────────────
       │    │
q_1: ──■────o────■───────
       │    │    │
q_2: ──■────┼────o────■──
     ┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐
q_3: ┤ X ├┤ X ├┤ X ├┤ X ├
     └───┘└───┘└───┘└───┘

Added a new class, PhaseOracle, has been added to the qiskit.circuit.library module. This class enables the construction of phase oracle circuits from Python boolean expressions.

from qiskit.circuit.library.phase_oracle import PhaseOracle

oracle = PhaseOracle('x1 & x2 & (not x3)')
oracle.draw('mpl')

These phase oracles can be used as part of a larger algorithm, for example with qiskit.algorithms.AmplificationProblem:

from qiskit.algorithms import AmplificationProblem, Grover
from qiskit import BasicAer

backend = BasicAer.get_backend('qasm_simulator')

problem = AmplificationProblem(oracle, is_good_state=oracle.evaluate_bitstring)
grover = Grover(quantum_instance=backend)
result = grover.amplify(problem)
result.top_measurement

'011'

The PhaseOracle class also includes a from_dimacs_file() method which enables constructing a phase oracle from a file describing a formula in the DIMACS-CNF format.

from qiskit.circuit.library.phase_oracle import PhaseOracle

oracle = PhaseOracle.from_dimacs_file("simple_v3_c2.cnf")
oracle.draw('text')

state_0: ─o───────o──────────────
          │ ┌───┐ │ ┌───┐
state_1: ─■─┤ X ├─■─┤ X ├─■──────
          │ └───┘   └───┘ │ ┌───┐
state_2: ─■───────────────o─┤ Z ├
                            └───┘

All transpiler passes (ie any instances of BasePass) are now directly callable. Calling a pass provides a convenient interface for running the pass on a QuantumCircuit object.

For example, running a single transformation pass, such as BasisTranslator, can be done with:

from qiskit import QuantumCircuit
from qiskit.transpiler.passes import BasisTranslator
from qiskit.circuit.equivalence_library import SessionEquivalenceLibrary as sel

circuit = QuantumCircuit(1)
circuit.h(0)

pass_instance = BasisTranslator(sel, ['rx', 'rz', 'cx'])
result = pass_instance(circuit)
result.draw(output='mpl')

When running an analysis pass, a property set (as dict or as PropertySet) needs to be added as a parameter and it might be modified « in-place ». For example:

from qiskit import QuantumCircuit
from qiskit.transpiler.passes import Depth

circuit = QuantumCircuit(1)
circuit.h(0)

property_set = {}
pass_instance = Depth()
pass_instance(circuit, property_set)
print(property_set)

{'depth': 1}

The QasmQobjConfig class now has an optional kwarg for meas_level and meas_return. These fields can be used to enable generating QasmQobj job payloads that support meas_level=1 (kerneled data) for circuit jobs (previously this was only exposed for PulseQobj objects). The assemble() function has been updated to set this field for QasmQobj objects it generates.
A new tensor() method has been added to the QuantumCircuit class. This method enables tensoring another circuit with an existing circuit. This method works analogously to qiskit.quantum_info.Operator.tensor() and is consistent with the little-endian convention of Qiskit.

For example:
from qiskit import QuantumCircuit top = QuantumCircuit(1) top.x(0); bottom = QuantumCircuit(2) bottom.cry(0.2, 0, 1); bottom.tensor(top).draw(output='mpl')
The qiskit.circuit.QuantumCircuit class now supports arbitrary free form metadata with the metadata attribute. A user (or program built on top of QuantumCircuit) can attach metadata to a circuit for use in tracking the circuit. For example:
```
from qiskit.circuit import QuantumCircuit

qc = QuantumCircuit(2, user_metadata_field_1='my_metadata',
                    user_metadata_field_2='my_other_value')
```
or:
```
from qiskit.circuit import QuantumCircuit

qc = QuantumCircuit(2)
qc.metadata = {'user_metadata_field_1': 'my_metadata',
               'user_metadata_field_2': 'my_other_value'}
```
This metadata will not be used for influencing the execution of the circuit but is just used for tracking the circuit for the lifetime of the object. The metadata attribute will persist between any circuit transforms including transpile() and assemble(). The expectation is for providers to associate the metadata in the result it returns, so that users can filter results based on circuit metadata the same way they can currently do with QuantumCircuit.name.
Add a new operator class CNOTDihedral has been added to the qiskit.quantum_info module. This class is used to represent the CNOT-Dihedral group, which is generated by the quantum gates CXGate, TGate, and XGate.
Adds a & (__and__) binary operator to BaseOperator subclasses (eg qiskit.quantum_info.Operator) in the qiskit.quantum_info module. This is shorthand to call the classes compose() method (ie A & B == A.compose(B)).

For example:
```
import qiskit.quantum_info as qi

qi.Pauli('X') & qi.Pauli('Y')
```
Adds a & (__and__) binary operator to qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix classes. This is shorthand to call the classes evolve() method (ie psi & U == psi.evolve(U)).

For example:
```
import qiskit.quantum_info as qi

qi.Statevector.from_label('0') & qi.Pauli('X')
```
A new a new 2-qubit gate, ECRGate, the echo cross-resonance (ECR), has been added to the qiskit.circuit.library module along with a corresponding method, ecr() for the QuantumCircuit class. The ECR gate is two \(CR(\frac{π}{4})\) pulses with an XGate between them for the echo. This gate is locally equivalent to a CXGate (can convert to a CNOT with local pre- or post-rotation). It is the native gate on current IBM hardware and compiling to it allows the pre-/post-rotations to be merged into the rest of the circuit.
A new kwarg approximation_degree has been added to the transpile() function for enabling approximate compilation. Valid values range from 0 to 1, and higher means less approximation. This is a heuristic dial to experiment with circuit approximations. The concrete interpretation of this number is left to each pass, which may use it to perform some approximate version of the pass. Specific examples include the UnitarySynthesis pass or the or translators to discrete gate sets. If a pass does not support this option, it implies exact transformation.
Two new transpiler passess, GateDirection and qiskit.transpiler.passes.CheckGateDirection, were added to the qiskit.transpiler.passes module. These new passes are inteded to be more general replacements for CXDirection and CheckCXDirection (which are both now deprecated, see the deprecation notes for more details) that perform the same function but work with other gates beside just CXGate.
When running on Windows, parallel execution with the parallel_map() function can now be enabled (it is still disabled by default). To do this you can either set parallel = True in a user config file, or set the QISKIT_PARALLEL environment variable to TRUE (this will also effect transpile() and assemble() which both use parallel_map() internally). It is important to note that when enabling parallelism on Windows there are limitations around how Python launches processes for Windows, see the Known Issues section below for more details on the limitations with parallel execution on Windows.
A new function, hellinger_distance(), for computing the Hellinger distance between two counts distributions has been added to the qiskit.quantum_info module.
The decompose_clifford() function in the qiskit.quantum_info module (which gets used internally by the qiskit.quantum_info.Clifford.to_circuit() method) has a new kwarg method which enables selecting the synthesis method used by either setting it to 'AG' or 'greedy'. By default for more than three qubits it is set to 'greedy' which uses a non-optimal greedy compilation routine for Clifford elements synthesis, by Bravyi et. al., which typically yields better CX cost compared to the previously used Aaronson-Gottesman method (for more than two qubits). You can use the method kwarg to revert to the previous default Aaronson-Gottesman method by setting method='AG'.
The Initialize class in the qiskit.extensions module can now be constructed using an integer. The “1” bits of the integer will insert a Reset and an XGate into the circuit for the corresponding qubit. This will be done using the standard little-endian convention is qiskit, ie the rightmost bit of the integer will set qubit 0. For example, setting the parameter in Initialize equal to 5 will set qubits 0 and 2 to value 1.
from qiskit.extensions import Initialize initialize = Initialize(13) initialize.definition.draw('mpl')
The Initialize class in the qiskit.extensions module now supports constructing directly from a Pauli label (analogous to the qiskit.quantum_info.Statevector.from_label() method). The Pauli label refer to basis states of the Pauli eigenstates Z, X, Y. These labels use Qiskit’s standard little-endian notation, for example a label of '01' would initialize qubit 0 to \(|1\rangle\) and qubit 1 to \(|0\rangle\).
from qiskit.extensions import Initialize initialize = Initialize("10+-lr") initialize.definition.draw('mpl')
The kwarg, template_list, for the constructor of the qiskit.transpiler.passes.TemplateOptimization transpiler pass now supports taking in a list of both QuantumCircuit and DAGDependency objects. Previously, only QuantumCircuit were accepted (which were internally converted to DAGDependency objects) in the input list.
A new transpiler pass, qiskit.transpiler.passes.RZXCalibrationBuilder, capable of generating calibrations and adding them to a quantum circuit has been introduced. This pass takes calibrated CXGate objects and creates the calibrations for qiskit.circuit.library.RZXGate objects with an arbitrary rotation angle. The schedules are created by stretching and compressing the GaussianSquare pulses of the echoed-cross resonance gates.
New template circuits for using qiskit.circuit.library.RZXGate are added to the qiskit.circuit.library module (eg rzx_yz). This enables pairing the TemplateOptimization pass with the qiskit.transpiler.passes.RZXCalibrationBuilder pass to automatically find and replace gate sequences, such as CNOT - P(theta) - CNOT, with more efficent circuits based on qiskit.circuit.library.RZXGate with a calibration.
The matplotlib output type for the circuit_drawer() and the draw() method for the QuantumCircuit class now supports configuration files for setting the visualization style. In previous releases, there was basic functionality that allowed users to pass in a style kwarg that took in a dict to customize the colors and other display features of the mpl drawer. This has now been expanded so that these dictionaries can be loaded from JSON files directly without needing to pass a dictionary. This enables users to create new style files and use that style for visualizations by passing the style filename as a string to the style kwarg.

To leverage this feature you must set the circuit_mpl_style_path option in a user config file. This option should be set to the path you want qiskit to search for style JSON files. If specifying multiple path entries they should be separated by :. For example, setting circuit_mpl_style_path = ~/.qiskit:~/user_styles in a user config file will look for JSON files in both ~/.qiskit and ~/user_styles.

A new kwarg, format_marginal has been added to the function marginal_counts() which when set to True formats the counts output according to the cregs in the circuit and missing indices are represented with a _. For example:

from qiskit import QuantumCircuit, execute, BasicAer, result
from qiskit.result.utils import marginal_counts
qc = QuantumCircuit(5, 5)
qc.x(0)
qc.measure(0, 0)

result = execute(qc, BasicAer.get_backend('qasm_simulator')).result()
print(marginal_counts(result.get_counts(), [0, 2, 4], format_marginal=True))

{'0_0_1': 1024}

Improved the performance of qiskit.quantum_info.Statevector.expectation_value() and qiskit.quantum_info.DensityMatrix.expectation_value() when the argument operator is a Pauli or SparsePauliOp operator.
The user config file has 2 new configuration options, num_processes and parallel, which are used to control the default behavior of parallel_map(). The parallel option is a boolean that is used to dictate whether parallel_map() will run in multiple processes or not. If it set to False calls to parallel_map() will be executed serially, while setting it to True will enable parallel execution. The num_processes option takes an integer which sets how many CPUs to use when executing in parallel. By default it will use the number of CPU cores on a system.
There are 2 new environment variables, QISKIT_PARALLEL and QISKIT_NUM_PROCS, that can be used to control the default behavior of parallel_map(). The QISKIT_PARALLEL option can be set to the TRUE (any capitalization) to set the default to run in multiple processes when parallel_map() is called. If it is set to any other value parallel_map() will be executed serially. QISKIT_NUM_PROCS takes an integer (for example QISKIT_NUM_PROCS=5) which will be used as the default number of processes to run with. Both of these will take precedence over the equivalent option set in the user config file.
A new method, gradient(), has been added to the ParameterExpression class. This method is used to evaluate the gradient of a ParameterExpression object.
The __eq__ method (ie what is called when the == operator is used) for the ParameterExpression now allows for the comparison with a numeric value. Previously, it was only possible to compare two instances of ParameterExpression with ==. For example:
```
from qiskit.circuit import Parameter

x = Parameter("x")
y = x + 2
y = y.assign(x, -1)

assert y == 1
```
The PauliFeatureMap class in the qiskit.circuit.library module now supports adjusting the rotational factor, \(\alpha\), by either setting using the kwarg alpha on the constructor or setting the alpha attribute after creation. Previously this value was fixed at 2.0. Adjusting this attribute allows for better control of decision boundaries and provides additional flexibility handling the input features without needing to explicitly scale them in the data set.
A new Gate class, PauliGate, has been added the qiskit.circuit.library module and corresponding method, pauli(), was added to the QuantumCircuit class. This new gate class enables applying several individual pauli gates to different qubits at the simultaneously. This is primarily useful for simulators which can use this new gate to more efficiently implement multiple simultaneous Pauli gates.
Improve the qiskit.quantum_info.Pauli operator. This class now represents and element from the full N-qubit Pauli group including complex coefficients. It now supports the Operator API methods including compose(), dot(), tensor() etc, where compose and dot are defined with respect to the full Pauli group.

This class also allows conversion to and from the string representation of Pauli’s for convenience.

For example
from qiskit.quantum_info import Pauli P1 = Pauli('XYZ') P2 = Pauli('YZX') P1.dot(P2)
Pauli('-iZXY')
Pauli’s can also be directly appended to QuantumCircuit objects
from qiskit import QuantumCircuit from qiskit.quantum_info import Pauli circ = QuantumCircuit(3) circ.append(Pauli('XYZ'), [0, 1, 2]) circ.draw(output='mpl')
Additional methods allow computing when two Pauli’s commute (using the commutes() method) or anticommute (using the anticommutes() method), and computing the Pauli resulting from Clifford conjugation \(P^\prime = C.P.C^\dagger\) using the evolve() method.

See the API documentation of the Pauli class for additional information.
A new function, random_pauli(), for generating a random element of the N-qubit Pauli group has been added to the qiskit.quantum_info module.
A new class, PiecewisePolynomialPauliRotations, has been added to the qiskit.circuit.library module. This circuit library element is used for mapping a piecewise polynomial function, \(f(x)\), which is defined through breakpoints and coefficients, on qubit amplitudes. The breakpoints \((x_0, ..., x_J)\) are a subset of \([0, 2^n-1]\), where \(n\) is the number of state qubits. The corresponding coefficients \([a_{j,1},...,a_{j,d}]\), where \(d\) is the highest degree among all polynomials. Then \(f(x)\) is defined as:

\[\begin{split}f(x) = \begin{cases} 0, x < x_0 \\ \sum_{i=0}^{i=d}a_{j,i} x^i, x_j \leq x < x_{j+1} \end{cases}\end{split}\]

where we implicitly assume \(x_{J+1} = 2^n\). And the mapping applied to the amplitudes is given by

\[F|x\rangle |0\rangle = \cos(p_j(x))|x\rangle |0\rangle + \sin(p_j(x))|x\rangle |1\rangle\]

This mapping is based on controlled Pauli Y-rotations and constructed using the PolynomialPauliRotations.
A new module qiskit.algorithms has been introduced. This module contains functionality equivalent to what has previously been provided by the qiskit.aqua.algorithms module (which is now deprecated) and provides the building blocks for constructing quantum algorithms. For details on migrating from qiskit-aqua to this new module please refer to the migration guide Qiskit Aqua Migration Guide
A new module qiskit.opflow has been introduced. This module contains functionality equivalent to what has previously been provided by the qiskit.aqua.operators module (which is now deprecated) and provides the operators and state functions which are used to build quantum algorithms. For details on migrating from qiskit-aqua to this new module please refer to the migration guide Qiskit Aqua Migration Guide
This is the first release that includes precompiled binary wheels for the for Linux aarch64 systems. If you are running a manylinux2014 compatible aarch64 Linux system there are now precompiled wheels available on PyPI, you are no longer required to build from source to install qiskit-terra.
The qiskit.quantum_info.process_fidelity() function is now able to be used with a non-unitary target channel. In this case the returned value is equivalent to the qiskit.quantum_info.state_fidelity() of the normalized qiskit.quantum_info.Choi matrices for the channels.

Note that the qiskit.quantum_info.average_gate_fidelity() and qiskit.quantum_info.gate_error() functions still require the target channel to be unitary and will raise an exception if it is not.

Added a new pulse builder function, qiskit.pulse.macro(). This enables normal Python functions to be decorated as macros. This enables pulse builder functions to be used within the decorated function. The builder macro can then be called from within a pulse building context, enabling code reuse.

For Example:

from qiskit import pulse

@pulse.macro
def measure(qubit: int):
    pulse.play(pulse.GaussianSquare(16384, 256, 15872),
               pulse.MeasureChannel(qubit))
    mem_slot = pulse.MemorySlot(0)
    pulse.acquire(16384, pulse.AcquireChannel(0), mem_slot)
    return mem_slot

with pulse.build(backend=backend) as sched:
    mem_slot = measure(0)
    print(f"Qubit measured into {mem_slot}")

sched.draw()

A new class, PauliTwoDesign, was added to the qiskit.circuit.library which implements a particular form of a 2-design circuit from https://arxiv.org/pdf/1803.11173.pdf For instance, this circuit can look like:
from qiskit.circuit.library import PauliTwoDesign circuit = PauliTwoDesign(4, reps=2, seed=5, insert_barriers=True) circuit.decompose().draw(output='mpl')
A new pulse drawer qiskit.visualization.pulse_v2.draw() (which is aliased as qiskit.visualization.pulse_drawer_v2) is now available. This new pulse drawer supports multiple new features not present in the original pulse drawer (pulse_drawer()).
- Truncation of long pulse instructions.
- Visualization of parametric pulses.
- New stylesheets IQXStandard, IQXSimple, IQXDebugging.
- Visualization of system info (channel frequency, etc…) by specifying qiskit.providers.Backend objects for visualization.
- Specifying axis objects for plotting to allow further extension of generated plots, i.e., for publication manipulations.
New stylesheets can take callback functions that dynamically modify the apperance of the output image, for example, reassembling a collection of channels, showing details of instructions, updating appearance of pulse envelopes, etc… You can create custom callback functions and feed them into a stylesheet instance to modify the figure appearance without modifying the drawer code. See pulse drawer module docstrings for details.

Note that file saving is now delegated to Matplotlib. To save image files, you need to call savefig method with returned Figure object.
Adds a reverse_qargs() method to the qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix classes. This method reverses the order of subsystems in the states and is equivalent to the qiskit.circuit.QuantumCircuit.reverse_bits() method for N-qubit states. For example:
from qiskit.circuit.library import QFT from qiskit.quantum_info import Statevector circ = QFT(3) state1 = Statevector.from_instruction(circ) state2 = Statevector.from_instruction(circ.reverse_bits()) state1.reverse_qargs() == state2
True
Adds a reverse_qargs() method to the qiskit.quantum_info.Operator class. This method reverses the order of subsystems in the operator and is equivalent to the qiskit.circuit.QuantumCircuit.reverse_bits() method for N-qubit operators. For example:
from qiskit.circuit.library import QFT from qiskit.quantum_info import Operator circ = QFT(3) op1 = Operator(circ) op2 = Operator(circ.reverse_bits()) op1.reverse_qargs() == op2
True
The latex output method for the qiskit.visualization.circuit_drawer() function and the draw() method now will use a user defined label on gates in the output visualization. For example:
```
import math

from qiskit.circuit import QuantumCircuit

qc = QuantumCircuit(2)
qc.h(0)
qc.rx(math.pi/2, 0, label='My Special Rotation')

qc.draw(output='latex')
```
The routing_method kwarg for the transpile() function now accepts a new option, 'none'. When routing_method='none' no routing pass will be run as part of the transpilation. If the circuit does not fit coupling map a TranspilerError exception will be raised.
A new gate class, RVGate, was added to the qiskit.circuit.library module along with the corresponding QuantumCircuit method rv(). The RVGate is a general rotation gate, similar to the UGate, but instead of specifying Euler angles the three components of a rotation vector are specified where the direction of the vector specifies the rotation axis and the magnitude specifies the rotation angle about the axis in radians. For example:
```
import math

import np

from qiskit.circuit import QuantumCircuit

qc = QuantumCircuit(1)
theta = math.pi / 5
phi = math.pi / 3
# RGate axis:
axis = np.array([math.cos(phi), math.sin(phi)])
rotation_vector = theta * axis
qc.rv(*rotation_vector, 0)
```
Unbound Parameter objects used in a QuantumCircuit object will now be sorted by name. This will take effect for the parameters returned by the parameters attribute. Additionally, the qiskit.circuit.QuantumCircuit.bind_parameters() and qiskit.circuit.QuantumCircuit.assign_parameters() methods can now take in a list of a values which will bind/assign them to the parameters in name-sorted order. Previously these methods would only take a dictionary of parameters and values. For example:
from qiskit.circuit import QuantumCircuit, Parameter circuit = QuantumCircuit(1) circuit.rx(Parameter('x'), 0) circuit.ry(Parameter('y'), 0) print(circuit.parameters) bound = circuit.bind_parameters([1, 2]) bound.draw(output='mpl')
ParameterView([Parameter(x), Parameter(y)])
The constructors for the qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix classes can now take a QuantumCircuit object in to build a Statevector and DensityMatrix object from that circuit, assuming that the qubits are initialized in \(|0\rangle\). For example:
from qiskit import QuantumCircuit from qiskit.quantum_info import Statevector qc = QuantumCircuit(2) qc.h(0) qc.cx(0, 1) statevector = Statevector(qc) statevector.draw(output='latex')
\[\begin{split}\begin{bmatrix} \tfrac{1}{\sqrt{2}} & 0 & 0 & \tfrac{1}{\sqrt{2}} \\ \end{bmatrix} \end{split}\]
New fake backend classes are available under qiskit.test.mock. These included mocked versions of ibmq_casablanca, ibmq_sydney, ibmq_mumbai, ibmq_lima, ibmq_belem, ibmq_quito. As with the other fake backends, these include snapshots of calibration data (i.e. backend.defaults()) and error data (i.e. backend.properties()) taken from the real system, and can be used for local testing, compilation and simulation.

Known Issues¶

Attempting to add an qiskit.pulse.Instruction object with a parameterized duration (ie the value of duration is an unbound Parameter or ParameterExpression object) to a qiskit.pulse.Schedule is not supported. Attempting to do so will result in UnassignedDurationError PulseError being raised. This is a limitation of how the Instruction overlap constraints are evaluated currently. This is supported by ScheduleBlock, in which the overlap constraints are evaluated just before the execution.

On Windows systems when parallel execution is enabled for parallel_map() parallelism may not work when called from a script running outside of a if __name__ == '__main__': block. This is due to how Python launches parallel processes on Windows. If a RuntimeError or AttributeError are raised by scripts that call parallel_map() (including using functions that use parallel_map() internally like transpile()) with Windows and parallelism enabled you can try embedding the script calls inside if __name__ == '__main__': to workaround the issue. For example:

from qiskit import QuantumCircuit, QiskitError
from qiskit import execute, Aer

qc1 = QuantumCircuit(2, 2)
qc1.h(0)
qc1.cx(0, 1)
qc1.measure([0,1], [0,1])
# making another circuit: superpositions
qc2 = QuantumCircuit(2, 2)
qc2.h([0,1])
qc2.measure([0,1], [0,1])
execute([qc1, qc2], Aer.get_backend('qasm_simulator'))

should be changed to:

from qiskit import QuantumCircuit, QiskitError
from qiskit import execute, Aer

def main():
    qc1 = QuantumCircuit(2, 2)
    qc1.h(0)
    qc1.cx(0, 1)
    qc1.measure([0,1], [0,1])
    # making another circuit: superpositions
    qc2 = QuantumCircuit(2, 2)
    qc2.h([0,1])
    qc2.measure([0,1], [0,1])
    execute([qc1, qc2], Aer.get_backend('qasm_simulator'))

if __name__ == '__main__':
    main()

if any errors are encountered with parallelism on Windows.

Upgrade Notes¶

The preset pass managers level_1_pass_manager, level_2_pass_manager, and level_3_pass_manager (which are used for optimization_level 1, 2, and 3 in the transpile() and execute() functions) now unconditionally use the Optimize1qGatesDecomposition pass for 1 qubit gate optimization. Previously, these pass managers would use the Optimize1qGates pass if the basis gates contained u1, u2, or u3. If you want to still use the old Optimize1qGates you will need to construct a custom PassManager with the pass.
Following transpilation of a parameterized QuantumCircuit, the global_phase attribute of output circuit may no longer be returned in a simplified form, if the global phase is a ParameterExpression.

For example:
```
qc = QuantumCircuit(1)
theta = Parameter('theta')

qc.rz(theta, 0)
qc.rz(-theta, 0)

print(transpile(qc, basis_gates=['p']).global_phase)
```
previously returned 0, but will now return -0.5*theta + 0.5*theta. This change was necessary was to avoid a large runtime performance penalty as simplifying symbolic expressions can be quite slow, especially if there are many ParameterExpression objects in a circuit.
The BasicAerJob job objects returned from BasicAer backends are now synchronous instances of JobV1. This means that calls to the run() will block until the simulation finishes executing. If you want to restore the previous async behavior you’ll need to wrap the run() with something that will run in a seperate thread or process like futures.ThreadPoolExecutor or futures.ProcessPoolExecutor.
The allow_sample_measuring option for the BasicAer simulator QasmSimulatorPy has changed from a default of False to True. This was done to better reflect the actual default behavior of the simulator, which would use sample measuring if the input circuit supported it (even if it was not enabled). If you are running a circuit that doesn’t support sample measurement (ie it has Reset operations or if there are operations after a measurement on a qubit) you should make sure to explicitly set this option to False when you call run().
The CommutativeCancellation transpiler pass is now aware of the target basis gates, which means it will only use gates in the specified basis. Previously, the pass would unconditionally replace consecutive gates which commute with ZGate with the U1Gate. However, now that the pass is basis aware and has a kwarg, basis_gates, for specifying the target basis there is a potential change in behavior if the kwarg is not set. When the basis_gates kwarg is not used and there are no variable z-rotation gates in the circuit then no commutative cancellation will occur.
Register (which is the parent class for QuantumRegister and ClassicalRegister and Bit (which is the parent class for Qubit and Clbit) objects are now immutable. In previous releases it was possible to adjust the value of a size or name attributes of a Register object and the index or register attributes of a Bit object after it was initially created. However this would lead to unsound behavior that would corrupt container structure that rely on a hash (such as a dict) since these attributes are treated as immutable properties of a register or bit (see #4705 for more details). To avoid this unsound behavior this attributes of a Register and Bit are no longer settable after initial creation. If you were previously adjusting the objects at runtime you will now need to create a new Register or Bit object with the new values.
The DAGCircuit.__eq__ method (which is used by the == operator), which is used to check structural equality of DAGCircuit and QuantumCircuit instances, will now include the global_phase and calibrations attributes in the fields checked for equality. This means that circuits which would have evaluated as equal in prior releases may not anymore if the global_phase or calibrations differ between the circuits. For example, in previous releases this would return True:
```
import math

from qiskit import QuantumCircuit

qc1 = QuantumCircuit(1)
qc1.x(0)

qc2 = QuantumCircuit(1, global_phase=math.pi)
qc2.x(0)

print(qc2 == qc1)
```
However, now because the global_phase attribute of the circuits differ this will now return False.
The previously deprecated qubits() and clbits() methods on the DAGCircuit class, which were deprecated in the 0.15.0 Terra release, have been removed. Instead you should use the qubits and clbits attributes of the DAGCircuit class. For example, if you were running:
```
from qiskit.dagcircuit import DAGCircuit

dag = DAGCircuit()
qubits = dag.qubits()
```
That would be replaced by:
```
from qiskit.dagcircuit import DAGCircuit

dag = DAGCircuit()
qubits = dag.qubits
```
The PulseDefaults returned by the fake pulse backends qiskit.test.mock.FakeOpenPulse2Q and qiskit.test.mock.FakeOpenPulse3Q have been updated to have more realistic pulse sequence definitions. If you are using these fake backend classes you may need to update your usage because of these changes.
The default synthesis method used by decompose_clifford() function in the quantum_info module (which gets used internally by the qiskit.quantum_info.Clifford.to_circuit() method) for more than 3 qubits now uses a non-optimal greedy compilation routine for Clifford elements synthesis, by Bravyi et. al., which typically yields better CX cost compared to the old default. If you need to revert to the previous Aaronson-Gottesman method this can be done by setting method='AG'.

The previously deprecated module qiskit.visualization.interactive, which was deprecated in the 0.15.0 release, has now been removed. Instead you should use the matplotlib based visualizations:

Removed Interactive function	Equivalent matplotlib function
`iplot_bloch_multivector`	`qiskit.visualization.plot_bloch_multivector()`
`iplot_state_city`	`qiskit.visualization.plot_state_city()`
`iplot_state_qsphere`	`qiskit.visualization.plot_state_qsphere()`
`iplot_state_hinton`	`qiskit.visualization.plot_state_hinton()`
`iplot_histogram`	`qiskit.visualization.plot_histogram()`
`iplot_state_paulivec`	`qiskit.visualization.plot_state_paulivec()`

The qiskit.Aer and qiskit.IBMQ top level attributes are now lazy loaded. This means that the objects will now always exist and warnings will no longer be raised on import if qiskit-aer or qiskit-ibmq-provider are not installed (or can’t be found by Python). If you were checking for the presence of qiskit-aer or qiskit-ibmq-provider using these module attributes and explicitly comparing to None or looking for the absence of the attribute this no longer will work because they are always defined as an object now. In other words running something like:
```
try:
    from qiskit import Aer
except ImportError:
    print("Aer not available")

or::

try:
    from qiskit import IBMQ
except ImportError:
    print("IBMQ not available")
```
will no longer work. Instead to determine if those providers are present you can either explicitly use qiskit.providers.aer.Aer and qiskit.providers.ibmq.IBMQ:
```
try:
    from qiskit.providers.aer import Aer
except ImportError:
    print("Aer not available")

try:
    from qiskit.providers.ibmq import IBMQ
except ImportError:
    print("IBMQ not available")
```
or check bool(qiskit.Aer) and bool(qiskit.IBMQ) instead, for example:
```
import qiskit

if not qiskit.Aer:
    print("Aer not available")
if not qiskit.IBMQ:
    print("IBMQ not available")
```
This change was necessary to avoid potential import cycle issues between the qiskit packages and also to improve the import time when Aer or IBMQ are not being used.
The user config file option suppress_packaging_warnings option in the user config file and the QISKIT_SUPPRESS_PACKAGING_WARNINGS environment variable no longer has any effect and will be silently ignored. The warnings this option controlled have been removed and will no longer be emitted at import time from the qiskit module.
The previously deprecated condition kwarg for qiskit.dagcircuit.DAGNode constructor has been removed. It was deprecated in the 0.15.0 release. Instead you should now be setting the classical condition on the Instruction object passed into the DAGNode constructor when creating a new op node.
When creating a new Register (which is the parent class for QuantumRegister and ClassicalRegister) or QuantumCircuit object with a number of bits (eg QuantumCircuit(2)), it is now required that number of bits are specified as an integer or another type which is castable to unambiguous integers(e.g. 2.0). Non-integer values will now raise an error as the intent in those cases was unclear (you can’t have fractional bits). For more information on why this was changed refer to: #4855
networkx is no longer a requirement for qiskit-terra. All the networkx usage inside qiskit-terra has been removed with the exception of 3 methods:
- qiskit.dagcircuit.DAGCircuit.to_networkx
- qiskit.dagcircuit.DAGCircuit.from_networkx
- qiskit.dagcircuit.DAGDependency.to_networkx
If you are using any of these methods you will need to manually install networkx in your environment to continue using them.
By default on macOS with Python >=3.8 parallel_map() will no longer run in multiple processes. This is a change from previous releases where the default behavior was that parallel_map() would launch multiple processes. This change was made because with newer versions of macOS with Python 3.8 and 3.9 multiprocessing is either unreliable or adds significant overhead because of the change in Python 3.8 to launch new processes with spawn instead of fork. To re-enable parallel execution on macOS with Python >= 3.8 you can use the user config file parallel option or set the environment variable QISKIT_PARALLEL to True.

The previously deprecated kwarg callback on the constructor for the PassManager class has been removed. This kwarg has been deprecated since the 0.13.0 release (April, 9th 2020). Instead you can pass the callback kwarg to the qiskit.transpiler.PassManager.run() method directly. For example, if you were using:

from qiskit.circuit.random import random_circuit
from qiskit.transpiler import PassManager

qc = random_circuit(2, 2)

def callback(**kwargs)
  print(kwargs['pass_'])

pm = PassManager(callback=callback)
pm.run(qc)

this can be replaced with:

from qiskit.circuit.random import random_circuit
from qiskit.transpiler import PassManager

qc = random_circuit(2, 2)

def callback(**kwargs)
  print(kwargs['pass_'])

pm = PassManager()
pm.run(qc, callback=callback)

It is now no longer possible to instantiate a base channel without a prefix, such as qiskit.pulse.Channel or qiskit.pulse.PulseChannel. These classes are designed to classify types of different user facing channel classes, such as qiskit.pulse.DriveChannel, but do not have a definition as a target resource. If you were previously directly instantiating either qiskit.pulse.Channel or qiskit.pulse.PulseChannel, this is no longer allowed. Please use the appropriate subclass.
When the require_cp and/or require_tp kwargs of qiskit.quantum_info.process_fidelity(), qiskit.quantum_info.average_gate_fidelity(), qiskit.quantum_info.gate_error() are True, they will now only log a warning rather than the previous behavior of raising a QiskitError exception if the input channel is non-CP or non-TP respectively.
The QFT class in the qiskit.circuit.library module now computes the Fourier transform using a little-endian representation of tensors, i.e. the state \(|1\rangle\) maps to \(|0\rangle - |1\rangle + |2\rangle - ..\) assuming the computational basis correspond to little-endian bit ordering of the integers. \(|0\rangle = |000\rangle, |1\rangle = |001\rangle\), etc. This was done to make it more consistent with the rest of Qiskit, which uses a little-endian convention for bit order. If you were depending on the previous bit order you can use the reverse_bits() method to revert to the previous behavior. For example:
```
from qiskit.circuit.library import QFT

qft = QFT(5).reverse_bits()
```
The qiskit.__qiskit_version__ module attribute was previously a dict will now return a custom read-only Mapping object that checks the version of qiskit elements at runtime instead of at import time. This was done to speed up the import path of qiskit and eliminate a possible import cycle by only importing the element packages at runtime if the version is needed from the package. This should be fully compatible with the dict previously return and for most normal use cases there will be no difference. However, if some applications were relying on either mutating the contents or explicitly type checking it may require updates to adapt to this change.
The qiskit.execute module has been renamed to qiskit.execute_function. This was necessary to avoid a potentical name conflict between the execute() function which is re-exported as qiskit.execute. qiskit.execute the function in some situations could conflict with qiskit.execute the module which would lead to a cryptic error because Python was treating qiskit.execute as the module when the intent was to the function or vice versa. The module rename was necessary to avoid this conflict. If you’re importing qiskit.execute to get the module (typical usage was from qiskit.execute import execute) you will need to update this to use qiskit.execute_function instead. qiskit.execute will now always resolve to the function.
The qiskit.compiler.transpile, qiskit.compiler.assemble, qiskit.compiler.schedule, and qiskit.compiler.sequence modules have been renamed to qiskit.compiler.transpiler, qiskit.compiler.assembler, qiskit.compiler.scheduler, and qiskit.compiler.sequence respectively. This was necessary to avoid a potentical name conflict between the modules and the re-exported function paths qiskit.compiler.transpile(), qiskit.compiler.assemble(), qiskit.compiler.schedule(), and qiskit.compiler.sequence(). In some situations this name conflict between the module path and re-exported function path would lead to a cryptic error because Python was treating an import as the module when the intent was to use the function or vice versa. The module rename was necessary to avoid this conflict. If you were using the imports to get the modules before (typical usage would be like``from qiskit.compiler.transpile import transpile``) you will need to update this to use the new module paths. qiskit.compiler.transpile(), qiskit.compiler.assemble(), qiskit.compiler.schedule(), and qiskit.compiler.sequence() will now always resolve to the functions.
The qiskit.quantum_info.Quaternion class was moved from the qiskit.quantum_info.operator submodule to the qiskit.quantum_info.synthesis submodule to better reflect it’s purpose. No change is required if you were importing it from the root qiskit.quantum_info module, but if you were importing from qiskit.quantum_info.operator you will need to update your import path.
Removed the QuantumCircuit.mcmt method, which has been deprecated since the Qiskit Terra 0.14.0 release in April 2020. Instead of using the method, please use the MCMT class instead to construct a multi-control multi-target gate and use the qiskit.circuit.QuantumCircuit.append() or qiskit.circuit.QuantumCircuit.compose() to add it to a circuit.

For example, you can replace:
```
circuit.mcmt(ZGate(), [0, 1, 2], [3, 4])
```
with:
```
from qiskit.circuit.library import MCMT
mcmt = MCMT(ZGate(), 3, 2)
circuit.compose(mcmt, range(5))
```
Removed the QuantumCircuit.diag_gate method which has been deprecated since the Qiskit Terra 0.14.0 release in April 2020. Instead, use the diagonal() method of QuantumCircuit.
Removed the QuantumCircuit.ucy method which has been deprecated since the Qiskit Terra 0.14.0 release in April 2020. Instead, use the ucry() method of QuantumCircuit.
The previously deprecated mirror() method for qiskit.circuit.QuantumCircuit has been removed. It was deprecated in the 0.15.0 release. The qiskit.circuit.QuantumCircuit.reverse_ops() method should be used instead since mirroring could be confused with swapping the output qubits of the circuit. The reverse_ops() method only reverses the order of gates that are applied instead of mirroring.
The previously deprecated support passing a float (for the scale kwarg as the first positional argument to the qiskit.circuit.QuantumCircuit.draw() has been removed. It was deprecated in the 0.12.0 release. The first positional argument to the qiskit.circuit.QuantumCircuit.draw() method is now the output kwarg which does not accept a float. Instead you should be using scale as a named kwarg instead of using it positionally.

For example, if you were previously calling draw with:
```
from qiskit import QuantumCircuit

qc = QuantumCircuit(2)
qc.draw(0.75, output='mpl')
```
this would now need to be:
```
from qiskit import QuantumCircuit

qc = QuantumCircuit(2)
qc.draw(output='mpl', scale=0.75)
```
or:
```
qc.draw('mpl', scale=0.75)
```

Features of Qiskit Pulse (qiskit.pulse) which were deprecated in the 0.15.0 release (August, 2020) have been removed. The full set of changes are:

Module	Old	New
`qiskit.pulse.library`	`SamplePulse`	`Waveform`
`qiskit.pulse.library`	`ConstantPulse`	`Constant`
(module rename)	`pulse.pulse_lib` Module	`qiskit.pulse.library`

Class	Old method	New method
`ParametricPulse`	`get_sample_pulse`	`get_waveform`
`Instruction`	`command`	N/A. Commands and Instructions have been unified. Use `operands()` to get information about the instruction data.
`Acquire`	`acquires`, `mem_slots`, `reg_slots`	`acquire()`, `mem_slot()`, `reg_slot()`. (The `Acquire` instruction no longer broadcasts across multiple qubits.)

The dictionary previously held on DAGCircuit edges has been removed. Instead, edges now hold the Bit instance which had previously been included in the dictionary as its 'wire' field. Note that the NetworkX graph returned by to_networkx() will still have a dictionary for its edge attributes, but the 'name' field will no longer be populated.
The parameters attribute of the QuantumCircuit class no longer is returning a set. Instead it returns a ParameterView object which implements all the methods that set offers (albeit deprecated). This was done to support a model that preserves name-sorted parameters. It should be fully compatible with any previous usage of the set returned by the parameters attribute, except for where explicit type checking of a set was done.
When running transpile() on a QuantumCircuit with delay() instructions, the units will be converted to dt if the value of dt (sample time) is known to transpile(), either explicitly via the dt kwarg or via the BackendConfiguration for a Backend object passed in via the backend kwarg.

The interpretation of meas_map (which is an attribute of a PulseBackendConfiguration object or as the corresponding meas_map kwarg on the schedule(), assemble(), sequence(), or execute() functions) has been updated to better match the true constraints of the hardware. The format of this data is a list of lists, where the items in the inner list are integers specifying qubit labels. For instance:

[[A, B, C], [D, E, F, G]]

Previously, the meas_map constraint was interpreted such that if one qubit was acquired (e.g. A), then all other qubits sharing a subgroup with that qubit (B and C) would have to be acquired at the same time and for the same duration. This constraint has been relaxed. One acquisition does not require more acquisitions. (If A is acquired, B and C do not need to be acquired.) Instead, qubits in the same measurement group cannot be acquired in a partially overlapping way – think of the meas_map as specifying a shared acquisition resource (If we acquire A from t=1000 to t=2000, we cannot acquire B starting from 1000<t<2000). For example:

# Good
meas_map = [[0, 1]]
# Acquire a subset of [0, 1]
sched = pulse.Schedule()
sched = sched.append(pulse.Acquire(10, acq_q0))

# Acquire 0 and 1 together (same start time, same duration)
sched = pulse.Schedule()
sched = sched.append(pulse.Acquire(10, acq_q0))
sched = sched.append(pulse.Acquire(10, acq_q1))

# Acquire 0 and 1 disjointly
sched = pulse.Schedule()
sched = sched.append(pulse.Acquire(10, acq_q0))
sched = sched.append(pulse.Acquire(10, acq_q1)) << 10

# Acquisitions overlap, but 0 and 1 aren't in the same measurement
# grouping
meas_map = [[0], [1]]
sched = pulse.Schedule()
sched = sched.append(pulse.Acquire(10, acq_q0))
sched = sched.append(pulse.Acquire(10, acq_q1)) << 1

# Bad: 0 and 1 are in the same grouping, but acquisitions
# partially overlap
meas_map = [[0, 1]]
sched = pulse.Schedule()
sched = sched.append(pulse.Acquire(10, acq_q0))
sched = sched.append(pulse.Acquire(10, acq_q1)) << 1

Deprecation Notes¶

Two new arguments have been added to qiskit.dagcircuit.DAGNode.semantic_eq(), bit_indices1 and bit_indices2, which are expected to map the Bit instances in each DAGNode to their index in qubits or clbits list of their respective DAGCircuit. During the deprecation period, these arguments are optional and when not specified the mappings will be automatically constructed based on the register and index properties of each Bit instance. However, in a future release, they will be required arguments and the mapping will need to be supplied by the user.
The pulse builder functions:
- qiskit.pulse.call_circuit()
- qiskit.pulse.call_schedule()
are deprecated and will be removed in a future release. These functions are unified into qiskit.pulse.call() which should be used instead.
The qiskit.pulse.Schedule method qiskit.pulse.Schedule.flatten() method is deprecated and will be removed in a future release. Instead you can use the qiskit.pulse.transforms.flatten() function which will perform the same operation.
The assign_parameters() for the following classes:
- qiskit.pulse.channels.Channel,
- qiskit.pulse.library.Pulse,
- qiskit.pulse.instructions.Instruction,
and all their subclasses is now deprecated and will be removed in a future release. This functionality has been subsumed ScheduleBlock which is the future direction for constructing parameterized pulse programs.
The parameters attribute for the following clasess:
- Channel
- Instruction.
is deprecated and will be removed in a future release. This functionality has been subsumed ScheduleBlock which is the future direction for constructing parameterized pulse programs.
Python 3.6 support has been deprecated and will be removed in a future release. When support is removed you will need to upgrade the Python version you’re using to Python 3.7 or above.

Two QuantumCircuit methods combine() and extend() along with their corresponding Python operators + and += are deprecated and will be removed in a future release. Instead the QuantumCircuit method compose() should be used. The compose() method allows more flexibility in composing two circuits that do not have matching registers. It does not, however, automatically add qubits/clbits unlike the deprecated methods. To add a circuit on new qubits/clbits, the qiskit.circuit.QuantumCircuit.tensor() method can be used. For example:

from qiskit.circuit import QuantumRegister, QuantumCircuit

a = QuantumRegister(2, 'a')
circuit_a = QuantumCircuit(a)
circuit_a.cx(0, 1)

b = QuantumRegister(2, 'b')
circuit_b = QuantumCircuit(b)
circuit_b.cz(0, 1)

# same as circuit_a + circuit_b (or combine)
added_with_different_regs = circuit_b.tensor(circuit_a)

# same as circuit_a + circuit_a (or combine)
added_with_same_regs = circuit_a.compose(circuit_a)

# same as circuit_a += circuit_b (or extend)
circuit_a = circuit_b.tensor(circuit_a)

# same as circuit_a += circuit_a (or extend)
circuit_a.compose(circuit_a, inplace=True)

Support for passing Qubit instances to the qubits kwarg of the qiskit.transpiler.InstructionDurations.get() method has been deprecated and will be removed in a future release. Instead, you should call the get() method with the integer indices of the desired qubits.
Using @ (__matmul__) for invoking the compose method of BaseOperator subclasses (eg Operator) is deprecated and will be removed in a future release. The qiskit.quantum_info.Operator.compose() method can be used directly or also invoked using the & (__and__) operator.
Using * (__mul__) for calling the dot() method of BaseOperator subclasses (eg qiskit.quantum_info.Operator) is deprecated and will be removed in a future release. Instead you can just call the dot() directly.
Using @ (__matmul__) for invoking the evolve() method of the qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix classes is deprecated and will be removed in a future release.. The evolve method can be used directly or also invoked using the & (__and__) operator.

The qiskit.pulse.schedule.ParameterizedSchedule class has been deprecated and will be removed in a future release. Instead you can directly parameterize pulse Schedule objects with a Parameter object, for example:

from qiskit.circuit import Parameter
from qiskit.pulse import Schedule
from qiskit.pulse import ShiftPhase, DriveChannel

theta = Parameter('theta')
target_schedule = Schedule()
target_schedule.insert(0, ShiftPhase(theta, DriveChannel(0)), inplace=True)

The qiskit.pulse.ScheduleComponent class in the qiskit.pulse module has been deprecated and will be removed in a future release. Its usage should be replaced either using a qiskit.pulse.Schedule or qiskit.pulse.Instruction directly. Additionally, the primary purpose of the ScheduleComponent class was as a common base class for both Schedule and Instruction for any place that was explicitly type checking or documenting accepting a ScheduleComponent input should be updated to accept Instruction or Schedule.
The JSON Schema files and usage for the IBMQ API payloads are deprecated and will be removed in a future release. This includes everything under the qiskit.schemas module and the qiskit.validation module. This also includes the validate kwargs for qiskit.qobj.QasmQobj.to_dict() and qiskit.qobj.QasmQobj.to_dict() along with the module level fastjsonschema validators in qiskit.qobj (which do not raise a deprecation warning). The schema files have been moved to the Qiskit/ibmq-schemas repository and those should be treated as the canonical versions of the API schemas. Moving forward only those schemas will recieve updates and will be used as the source of truth for the schemas. If you were relying on the schemas bundled in qiskit-terra you should update to use that repository instead.
The qiskit.util module has been deprecated and will be removed in a future release. It has been replaced by qiskit.utils which provides the same functionality and will be expanded in the future. Note that no DeprecationWarning will be emitted regarding this deprecation since it was not feasible on Python 3.6.
The CXDirection transpiler pass in the qiskit.transpiler.passes module has been deprecated and will be removed in a future release. Instead the GateDirection should be used. It behaves identically to the CXDirection except that it now also supports transforming a circuit with ECRGate gates in addition to CXGate gates.
The CheckCXDirection transpiler pass in the qiskit.transpiler.passes module has been deprecated and will be removed in a future release. Instead the CheckGateDirection pass should be used. It behaves identically to the CheckCXDirection except that it now also supports checking the direction of all 2-qubit gates, not just CXGate gates.
The WeightedAdder method num_ancilla_qubits() is deprecated and will be removed in a future release. It has been replaced with the qiskit.circuit.library.WeightedAdder.num_ancillas attribute which is consistent with other circuit libraries” APIs.
The following legacy methods of the qiskit.quantum_info.Pauli class have been deprecated. See the method documentation for replacement use in the updated Pauli class.
- from_label()
- sgn_prod()
- to_spmatrix()
- kron()
- update_z()
- update_x()
- insert_paulis()
- append_paulis()
- delete_qubits()
- pauli_single()
- random()
Using a list or numpy.ndarray as the channel or target argument for the qiskit.quantum_info.process_fidelity(), qiskit.quantum_info.average_gate_fidelity(), qiskit.quantum_info.gate_error(), and qiskit.quantum_info.diamond_norm() functions has been deprecated and will not be supported in a future release. The inputs should instead be a Gate or a BaseOperator subclass object (eg. Operator, Choi, etc.)
Accessing references from Qubit and Clbit instances to their containing registers via the register or index properties has been deprecated and will be removed in a future release. Instead, Register objects can be queried to find the Bit objects they contain.
The current functionality of the qiskit.visualization.pulse_drawer() function is deprecated and will be replaced by qiskit.visualization.pulse_drawer_v2() (which is not backwards compatible) in a future release.
The use of methods inherited from the set type on the output of the parameters attribute (which used to be a set) of the QuantumCircuit class are deprecated and will be removed in a future release. This includes the methods from the add(), difference(), difference_update(), discard(), intersection(), intersection_update(), issubset(), issuperset(), symmetric_difference(), symmetric_difference_update(), union(), update(), __isub__() (which is the -= operator), and __ixor__() (which is the ^= operator).
The name of the first (and only) positional argument for the qiskit.circuit.QuantumCircuit.bind_parameters() method has changed from value_dict to values. The passing an argument in with the name values_dict is deprecated and will be removed in future release. For example, if you were previously calling bind_parameters() with a call like: bind_parameters(values_dict={}) this is deprecated and should be replaced by bind_parameters(values={}) or even better just pass the argument positionally bind_parameters({}).
The name of the first (and only) positional argument for the qiskit.circuit.QuantumCircuit.assign_parameters() method has changed from param_dict to parameters. Passing an argument in with the name param_dict is deprecated and will be removed in future release. For example, if you were previously calling assign_parameters() with a call like: assign_parameters(param_dict={}) this is deprecated and should be replaced by assign_parameters(values={}) or even better just pass the argument positionally assign_parameters({}).

Bug Fixes¶

Fixed an issue where the execute() function would raise QiskitError exception when a ParameterVector object was passed in for the parameter_bind kwarg. parameter. For example, it is now possible to call something like:
```
execute(circuit, backend, parameter_binds=[{pv1: [...], pv2: [...]}])
```
where pv1 and pv2 are ParameterVector objects. Fixed #5467
Fixed an issue with the labels of parametric pulses in the PulseQobjInstruction class were not being properly set as they are with sampled pulses. This also means that pulse names that are imported from the PulseDefaults returned by a Backend, such as x90, x90m, etc, will properly be set. Fixed #5363
Fixed an issue where unbound parameters only occurring in the global_phase attribute of a QuantumCircuit object would not show in the parameters attribute and could not be bound. Fixed #5806
The calibrations attribute of QuantumCircuit objects are now preserved when the += (ie the extend() method) and the + (ie the combine() method) are used. Fixed #5930 and #5908
The name setter method of class Register (which is the parent class of QuantumRegister and ClassicalRegister) previously did not check if the assigned string was a valid register name as per the OpenQASM specification. This check was previously only performed when the name was specified in the constructor, this has now been fixed so that setting the name attribute directly with an invalid value will now also raise an exception. Fixed #5461
Fixed an issue with the qiskit.visualization.circuit_drawer() function and qiskit.circuit.QuantumCircuit.draw() method when visualizing a QuantumCircuit with a Gate that has a classical condition after a Measure that used the same ClassicalRegister, it was possible for the conditional Gate to be displayed to the left of the Measure. Fixed #5387
In the transpiler pass qiskit.transpiler.passes.CSPLayout a bias towards lower numbered qubits could be observed. This undesireable bias has been fixed by shuffling the candidates to randomize the results. Furthermore, the usage of the CSPLayout pass in the preset_passmanagers (for level 2 and 3) has been adjusted to use a configured seed if the seed_transpiler kwarg is set when transpile() is called. Fixed #5990
Fixes a bug where the channels field for a PulseBackendConfiguration object was not being included in the output of the qiskit.providers.models.PulseBackendConfiguration.to_dict method. Fixed #5579
Fixed the 'circular' entanglement in the qiskit.circuit.library.NLocal circuit class for the edge case where the circuit has the same size as the entanglement block (e.g. a two-qubit circuit and CZ entanglement gates). In this case there should only be one entanglement gate, but there was accidentially added a second one in the inverse direction as the first. Fixed Qiskit/qiskit-aqua#1452
Fixed the handling of breakpoints in the PiecewisePolynomialPauliRotations class in the qiskit.circuit.library. Now for n intervals, n+1 breakpoints are allowed. This enables specifying another end interval other than \(2^\text{num qubits}\). This is important because from the end of the last interval to \(2^\text{num qubits}\) the function is the identity.
Fixed an issue in the qiskit.circuit.library.Permutation circuit class where some permutations would not be properly generated. This issue could also effect qiskit.circuit.library.QuantumVolume if it were called with classical_permutation=False`. Fixed #5812
Fixed an issue where generating QASM output with the qasm() method for a QuantumCircuit object that has a ControlledGate with an open control the output would be as if all controls were closed independent of the specified control state. This would result in a different circuit being created from from_qasm_str() if parsing the generated QASM.

This was fixed by updating the QASM output from qasm() by defining a composite gate which uses XGate to implement the open controls. The composite gate is named like <original_gate_name>_o<ctrl_state> where o stands for open control and ctrl_state is the integer value of the control state. Fixed #5443
Fixed an issue where binding Parameter objects in a QuantumCircuit with the parameter_binds in the execute function would cause all the bound QuantumCircuit objects would have the same name, which meant the result names were also not unique. This fix causes the bind_parameters() and assign_parameters() to assign a unique circuit name when inplace=False as:
```
<base name>-<class instance no.>[-<pid name>]
```
where <base name> is the name supplied by the « name » kwarg, otherwise it defaults to « circuit ». The class instance number gets incremented every time an instance of the class is generated. <pid name> is appended if called outside the main process. Fixed #5185
Fixed an issue with the scheduler() function where it would raise an exception if an input circuit contained an unbound QuantumCircuit object. Fixed #5304
Fixed an issue in the qiskit.transpiler.passes.TemplateOptimization transpiler passes where template circuits that contained unbound Parameter objects would crash under some scenarios if the parameters could not be bound during the template matching. Now, if the Parameter objects can not be bound templates with unbound Parameter are discarded and ignored by the TemplateOptimization pass. Fixed #5533
Fixed an issue with the qiskit.visualization.timeline_drawer() function where classical bits were inproperly handled. Fixed #5361
Fixed an issue in the qiskit.visualization.circuit_drawer() function and the qiskit.circuit.QuantumCircuit.draw() method where Delay instructions in a QuantumCircuit object were not being correctly treated as idle time. So when the idle_wires kwarg was set to False the wires with the Delay objects would still be shown. This has been fixed so that the idle wires are removed from the visualization if there are only Delay objects on a wire.
Previously, when the option layout_method kwarg was provided to the transpile() function and the optimization_level kwarg was set to >= 2 so that the pass qiskit.transpiler.passes.CSPLayout would run, if CSPLayout found a solution then the method in layout_method was not executed. This has been fixed so that if specified, the layout_method is always honored. Fixed #5409

When the argument coupling_map=None (either set explicitly, set implicitly as the default value, or via the backend kwarg), the transpiling process was not « embedding » the circuit. That is, even when an initial_layout was specified, the virtual qubits were not assigned to physical qubits. This has been fixed so that now, the qiskit.compiler.transpile() function honors the initial_layout argument by embedding the circuit:

from qiskit import QuantumCircuit, QuantumRegister
from qiskit.compiler import transpile

qr = QuantumRegister(2, name='qr')
circ = QuantumCircuit(qr)
circ.h(qr[0])
circ.cx(qr[0], qr[1])

transpile(circ, initial_layout=[1, 0]).draw(output='mpl')

If the initial_layout refers to more qubits than in the circuit, the transpiling process will extended the circuit with ancillas.

from qiskit import QuantumCircuit, QuantumRegister
from qiskit.compiler import transpile

qr = QuantumRegister(2, name='qr')
circ = QuantumCircuit(qr)
circ.h(qr[0])
circ.cx(qr[0], qr[1])

transpile(circ, initial_layout=[4, 2], coupling_map=None).draw()

                         
ancilla_0 -> 0 ──────────

ancilla_1 -> 1 ──────────
                    ┌───┐
     qr_1 -> 2 ─────┤ X ├
                    └─┬─┘
ancilla_2 -> 3 ───────┼──
               ┌───┐  │  
     qr_0 -> 4 ┤ H ├──■──
               └───┘

Fixed #5345

A new kwarg, user_cost_dict has been added to the constructor for the qiskit.transpiler.passes.TemplateOptimization transpiler pass. This enables users to provide a custom cost dictionary for the gates to the underlying template matching algorithm. For example:
```
from qiskit.transpiler.passes import TemplateOptimization

cost_dict = {'id': 0, 'x': 1, 'y': 1, 'z': 1, 'h': 1, 't': 1}
pass = TemplateOptimization(user_cost_dict=cost_dict)
```
An issue when passing the Counts object returned by get_counts() to marginal_counts() would produce an improperly formatted Counts object with certain inputs has been fixed. Fixes #5424
Improved the allocation of helper qubits in PolynomialPauliRotations and PiecewiseLinearPauliRotations which makes the implementation of these circuit more efficient. Fixed #5320 and #5322
Fix the usage of the allocated helper qubits in the MCXGate in the WeightedAdder class. These were previously allocated but not used prior to this fix. Fixed #5321
In a number of cases, the latex output method for the qiskit.visualization.circuit_drawer() function and the draw() method did not display the gate name correctly, and in other cases, did not include gate parameters where they should be. Now the gate names will be displayed the same way as they are displayed with the mpl output method, and parameters will display for all the gates that have them. In addition, some of the gates did not display in the correct form, and these have been fixed. Fixes #5605, #4938, and #3765
Fixed an issue where, if the qiskit.circuit.Instruction.to_instruction() method was used on a subcircuit which contained classical registers and that Instruction object was then added to a QuantumCircuit object, then the output from the qiskit.visualization.circuit_drawer() function and the qiskit.circuit.QuantumCircuit.draw() method would in some instances display the subcircuit to the left of a measure when it should have been displayed to the right. Fixed #5947
Fixed an issue with Delay objects in a QuantumCircuit where qiskit.compiler.transpile() would not be convert the units of the Delay to the units of the Backend, if the backend kwarg is set on transpile(). This could result in the wrong behavior because of a unit mismatch, for example running:
```
from qiskit import transpile, execute
from qiskit.circuit import QuantumCircuit

qc = QuantumCircuit(1)
qc.delay(100, [0], unit='us')

qc = transpile(qc, backend)
job = execute(qc, backend)
```
would previously have resulted in the backend delay for 100 timesteps (each of duration dt) rather than expected (100e-6 / dt) timesteps. This has been corrected so the qiskit.compiler.transpile() function properly converts the units.

Other Notes¶

The snapshots of all the fake/mock backends in qiskit.test.mock have been updated to reflect recent device changes. This includes a change in the basis_gates attribute for the BackendConfiguration to ['cx', 'rz', 'sx', 'x', 'id'], the addition of a readout_length property to the qubit properties in the BackendProperties, and updating the PulseDefaults so that all the mock backends support parametric pulse based InstructionScheduleMap instances.

Aer 0.8.0¶

Prelude¶

The 0.8 release includes several new features and bug fixes. The highlights for this release are: the introduction of a unified AerSimulator backend for running circuit simulations using any of the supported simulation methods; a simulator instruction library (qiskit.providers.aer.library) which includes custom instructions for saving various kinds of simulator data; MPI support for running large simulations on a distributed computing environment.

New Features¶

Python 3.9 support has been added in this release. You can now run Qiskit Aer using Python 3.9 without building from source.
Add the CMake flag DISABLE_CONAN (default=``OFF``)s. When installing from source, setting this to ON allows bypassing the Conan package manager to find libraries that are already installed on your system. This is also available as an environment variable DISABLE_CONAN, which takes precedence over the CMake flag. This is not the official procedure to build AER. Thus, the user is responsible of providing all needed libraries and corresponding files to make them findable to CMake.
This release includes support for building qiskit-aer with MPI support to run large simulations on a distributed computing environment. See the contributing guide for instructions on building and running in an MPI environment.
It is now possible to build qiskit-aer with CUDA enabled in Windows. See the contributing guide for instructions on building from source with GPU support.
When building the qiskit-aer Python extension from source several build dependencies need to be pre-installed to enable C++ compilation. As a user convenience when building the extension any of these build dependencies which were missing would be automatically installed using pip prior to the normal setuptools installation steps, however it was previously was not possible to avoid this automatic installation. To solve this issue a new environment variable DISABLE_DEPENDENCY_INSTALL has been added. If it is set to 1 or ON when building the python extension from source this will disable the automatic installation of these missing build dependencies.
Adds support for optimized N-qubit Pauli gate ( qiskit.circuit.library.PauliGate) to the StatevectorSimulator, UnitarySimulator, and the statevector and density matrix methods of the QasmSimulator and AerSimulator.
The run() method for the AerSimulator, QasmSimulator, StatevectorSimulator, and UnitarySimulator backends now takes a QuantumCircuit (or a list of QuantumCircuit objects) as it’s input. The previous QasmQobj object is still supported for now, but will be deprecated in a future release.

For an example of how to use this see:
```
from qiskit import transpile, QuantumCircuit

from qiskit.providers.aer import Aer

backend = Aer.get_backend('aer_simulator')

circuit = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()

tqc = transpile(circuit, backend)
result = backend.run(tqc, shots=4096).result()
```
The run() method for the PulseSimulator backend now takes a Schedule (or a list of Schedule objects) as it’s input. The previous PulseQobj object is still supported for now, but will be deprecated in a future release.
Adds the new AerSimulator simulator backend supporting the following simulation methods
- automatic
- statevector
- stabilizer
- density_matrix
- matrix_product_state
- unitary
- superop
The default automatic method will automatically choose a simulation method separately for each run circuit based on the circuit instructions and noise model (if any). Initializing a simulator with a specific method can be done using the method option.

GPU simulation for the statevector, density matrix and unitary methods can be enabled by setting the device='GPU' backend option.

Note that the unitary and superop methods do not support measurement as they simulate the unitary matrix or superoperator matrix of the run circuit so one of the new save_unitary(), save_superop(), or save_state() instructions must be used to save the simulator state to the returned results. Similarly state of the other simulations methods can be saved using the appropriate instructions. See the qiskit.providers.aer.library API documents for more details.

Note that the AerSimulator simulator superceds the QasmSimulator, StatevectorSimulator, and UnitarySimulator backends which will be deprecated in a future release.
Updates the AerProvider class to include multiple AerSimulator backends preconfigured for all available simulation methods and simulation devices. The new backends can be accessed through the provider interface using the names
- "aer_simulator"
- "aer_simulator_statevector"
- "aer_simulator_stabilizer"
- "aer_simulator_density_matrix"
- "aer_simulator_matrix_product_state"
- "aer_simulator_extended_stabilizer"
- "aer_simulator_unitary"
- "aer_simulator_superop"
Additional if Aer was installed with GPU support on a compatible system the following GPU backends will also be available
- "aer_simulator_statevector_gpu"
- "aer_simulator_density_matrix_gpu"
- "aer_simulator_unitary_gpu"
For example:
```
from qiskit import Aer

# Get the GPU statevector simulator backend
backend = Aer.get_backend('aer_simulator_statevector_gpu')
```
Added a new norm estimation method for performing measurements when using the "extended_stabilizer" simulation method. This norm estimation method can be used by passing the following options to the AerSimulator and QasmSimulator backends
```
simulator = QasmSimulator(
    method='extended_stabilizer',
    extended_stabilizer_sampling_method='norm_estimation')
```
The norm estimation method is slower than the alternative metropolis or resampled_metropolis options, but gives better performance on circuits with sparse output distributions. See the documentation of the QasmSimulator for more information.
Adds instructions for saving the state of the simulator in various formats. These instructions are
These instructions can be appended to a quantum circuit by using the save_density_matrix, save_matrix_product_state, save_stabilizer, save_state, save_statevector, save_statevector_dict, save_unitary circuit methods which are added to QuantumCircuit when importing Aer.

See the qiskit.providers.aer.library API documentation for details on method compatibility for each instruction.

Note that the snapshot instructions SnapshotStatevector, SnapshotDensityMatrix, SnapshotStabilizer are still supported but will be deprecated in a future release.
Adds qiskit.providers.aer.library.SaveExpectationValue and qiskit.providers.aer.library.SaveExpectationValueVariance quantum circuit instructions for saving the expectation value \(\langle H\rangle = Tr[H\rho]\), or expectation value and variance \(Var(H) = \langle H^2\rangle - \langle H\rangle^2\), of a Hermitian operator \(H\) for the simulator state \(\rho\). These instruction can be appended to a quantum circuit by using the save_expectation_value and save_expectation_value_variance circuit methods which is added to QuantumCircuit when importing Aer.

Note that the snapshot instruction SnapshotExpectationValue, is still supported but will be deprecated in a future release.
Adds qiskit.providers.aer.library.SaveProbabilities and qiskit.providers.aer.library.SaveProbabilitiesDict quantum circuit instruction for saving all measurement outcome probabilities for Z-basis measurements of the simualtor state. These instruction can be appended to a quantum circuit by using the save_probabilities and save_probabilities_dict circuit methods which is added to QuantumCircuit when importing Aer.

Note that the snapshot instruction SnapshotProbabilities, is still supported but will be deprecated in a future release.
Adds qiskit.providers.aer.library.SaveAmplitudes and qiskit.providers.aer.library.SaveAmplitudesSquared circuit instructions for saving select complex statevector amplitudes, or select probabilities (amplitudes squared) for supported simulation methods. These instructions can be appended to a quantum circuit by using the save_amplitudes and save_amplitudes_squared circuit methods which is added to QuantumCircuit when importing Aer.
Adds instructions for setting the state of the simulators. These instructions must be defined on the full number of qubits in the circuit. They can be applied at any point in a circuit and will override the simulator state with the one specified. Added instructions are
These instruction can be appended to a quantum circuit by using the set_density_matrix, set_stabilizer, set_statevector, set_unitary circuit methods which are added to QuantumCircuit when importing Aer.

See the qiskit.providers.aer.library API documentation for details on method compatibility for each instruction.
Added support for diagonal gates to the "matrix_product_state" simulation method.
Added support for the initialize instruction to the "matrix_product_state" simulation method.

Known Issues¶

There is a known issue where the simulation of certain circuits with a Kraus noise model using the "matrix_product_state" simulation method can cause the simulator to crash. Refer to #306 for more information.

Upgrade Notes¶

The minimum version of Conan has been increased to 1.31.2. This was necessary to fix a compatibility issue with newer versions of the urllib3 (which is a dependency of Conan). It also adds native support for AppleClang 12 which is useful for users with new Apple computers.
pybind11 minimum version required is 2.6 instead of 2.4. This is needed in order to support CUDA enabled compilation in Windows.
Cython has been removed as a build dependency.
Removed x90 gate decomposition from noise models that was deprecated in qiskit-aer 0.7. This decomposition is now done by using regular noise model basis gates and the qiskit transpiler.
The following options for the "extended_stabilizer" simulation method have changed.
- extended_stabilizer_measure_sampling: This option has been replaced by the options extended_stabilizer_sampling_method, which controls how we simulate qubit measurement.
- extended_stabilizer_mixing_time: This option has been renamed as extended_stabilizer_metropolis_mixing_time to clarify it only applies to the metropolis and resampled_metropolis sampling methods.
- extended_stabilizer_norm_estimation_samples: This option has been renamed to extended_stabilizer_norm_estimation_default_samples.
One additional option, extended_stabilizer_norm_estimation_repetitions has been added, whih controls part of the behaviour of the norm estimation sampling method.

Deprecation Notes¶

Python 3.6 support has been deprecated and will be removed in a future release. When support is removed you will need to upgrade the Python version you’re using to Python 3.7 or above.

Bug Fixes¶

Fixes bug with AerProvider where options set on the returned backends using set_options() were stored in the provider and would persist for subsequent calls to get_backend() for the same named backend. Now every call to and backends() returns a new instance of the simulator backend that can be configured.
Fixes bug in the error message returned when a circuit contains unsupported simulator instructions. Previously some supported instructions were also being listed in the error message along with the unsupported instructions.
Fixes issue with setting QasmSimulator basis gates when using "method" and "noise_model" options together, and when using them with a simulator constructed using from_backend(). Now the listed basis gates will be the intersection of gates supported by the backend configuration, simulation method, and noise model basis gates. If the intersection of the noise model basis gates and simulator basis gates is empty a warning will be logged.
Fix bug where the "sx"` gate SXGate was not listed as a supported gate in the C++ code, in StateOpSet of matrix_product_state.hp.
Fix bug where "csx", "cu2", "cu3" were incorrectly listed as supported basis gates for the "density_matrix" method of the QasmSimulator.
Fix bug where parameters were passed incorrectly between functions in matrix_product_state_internal.cpp, causing wrong simulation, as well as reaching invalid states, which in turn caused an infinite loop.
Fixes a bug that resulted in c_if not working when the width of the conditional register was greater than 64. See #1077.
Fixes a bug #1153) where noise on conditional gates was always being applied regardless of whether the conditional gate was actually applied based on the classical register value. Now noise on a conditional gate will only be applied in the case where the conditional gate is applied.
Fixes a bug with nested OpenMP flag was being set to true when it shouldn’t be.
Fixes a bug when applying truncation in the matrix product state method of the QasmSimulator.
Fixed issue #1126: bug in reporting measurement of a single qubit. The bug occured when copying the measured value to the output data structure.
In MPS, apply_kraus was operating directly on the input bits in the parameter qubits, instead of on the internal qubits. In the MPS algorithm, the qubits are constantly moving around so all operations should be applied to the internal qubits.
When invoking MPS::sample_measure, we need to first sort the qubits to the default ordering because this is the assumption in qasm_controller.This is done by invoking the method move_all_qubits_to_sorted_ordering. It was correct in sample_measure_using_apply_measure, but missing in sample_measure_using_probabilities.
Fixes bug with the from_backend() method of the QasmSimulator that would set the local attribute of the configuration to the backend value rather than always being set to True.
Fixes bug in from_backend() and from_backend() where basis_gates was set incorrectly for IBMQ devices with basis gate set ['id', 'rz', 'sx', 'x', 'cx']. Now the noise model will always have the same basis gates as the backend basis gates regardless of whether those instructions have errors in the noise model or not.
Fixes an issue where the Extended « extended_stabilizer » simulation method would give incorrect results on quantum circuits with sparse output distributions. Refer to #306 for more information and examples.

Ignis 0.6.0¶

New Features¶

The qiskit.ignis.mitigation.expval_meas_mitigator_circuits() function has been improved so that the number of circuits generated by the function used for calibration by the CTMP method are reduced from \(O(n)\) to \(O(\log{n})\) (where \(n\) is the number of qubits).

Upgrade Notes¶

The qiskit.ignis.verification.randomized_benchmarking_seq() function is now using the upgraded CNOTDihedral class, qiskit.ignis.verification.CNOTDihedral, which enables performing CNOT-Dihedral Randomized Benchmarking on more than two qubits.
The python package retworkx is now a requirement for installing qiskit-ignis. It replaces the previous usage of networkx (which is no longer a requirement) to get better performance.
The scikit-learn dependency is no longer required and is now an optional requirement. If you’re using the IQ measurement discriminators (IQDiscriminationFitter, LinearIQDiscriminationFitter, QuadraticIQDiscriminationFitter, or SklearnIQDiscriminator) you will now need to manually install scikit-learn, either by running pip install scikit-learn or when you’re also installing qiskit-ignis with pip install qiskit-ignis[iq].

Bug Fixes¶

Fixed an issue in the expectation value method expectation_value(), for the error mitigation classes TensoredExpvalMeasMitigator and CTMPExpvalMeasMitigator if the qubits kwarg was not specified it would incorrectly use the total number of qubits of the mitigator, rather than the number of classical bits in the count dictionary leading to greatly reduced performance. Fixed #561
Fix the "auto" method of the TomographyFitter, StateTomographyFitter, and ProcessTomographyFitter to only use "cvx" if CVXPY is installed and a third-party SDP solver other than SCS is available. This is because the SCS solver has lower accuracy than other solver methods and often returns a density matrix or Choi-matrix that is not completely-positive and fails validation when used with the qiskit.quantum_info.state_fidelity() or qiskit.quantum_info.process_fidelity() functions.

Aqua 0.9.0¶

This release officially deprecates the Qiskit Aqua project, in the future (no sooner than 3 months from this release) the Aqua project will have it’s final release and be archived. All the functionality that qiskit-aqua provides has been migrated to either new packages or to other qiskit packages. The application modules that are provided by qiskit-aqua have been split into several new packages: qiskit-optimization, qiskit-nature, qiskit-machine-learning, and qiskit-finance. These packages can be installed by themselves (via the standard pip install command, ie pip install qiskit-nature) or with the rest of the Qiskit metapackage as optional extras (ie, pip install 'qiskit[finance,optimization]' or pip install 'qiskit[all]'. The core building blocks for algorithms and the operator flow now exist as part of qiskit-terra at qiskit.algorithms and qiskit.opflow. Depending on your existing usage of Aqua you should either use the application packages or the new modules in Qiskit Terra.

For more details on how to migrate from using Qiskit Aqua you can refer to the Qiskit Aqua Migration Guide.

IBM Q Provider 0.12.2¶

No change

Qiskit 0.24.1¶

Terra 0.16.4¶

No change

Aer 0.7.6¶

No change

Ignis 0.5.2¶

No change

Aqua 0.8.2¶

No change

IBM Q Provider 0.12.2¶

Upgrade Notes¶

qiskit.providers.ibmq.IBMQBackend.defaults() now returns the pulse defaults for the backend if the backend supports pulse. However, your provider may not support pulse even if the backend does. The open_pulse flag in backend configuration indicates whether the provider supports it.

Qiskit 0.24.0¶

Terra 0.16.4¶

No change

Aer 0.7.6¶

New Features¶

This is the first release of qiskit-aer that publishes precompiled binaries to PyPI for Linux on aarch64 (arm64). From this release onwards Linux aarch64 packages will be published and supported.

Bug Fixes¶

Fixes a bug #1153 where noise on conditional gates was always being applied regardless of whether the conditional gate was actually applied based on the classical register value. Now noise on a conditional gate will only be applied in the case where the conditional gate is applied.
Fixed issue #1126: bug in reporting measurement of a single qubit. The bug occured when copying the measured value to the output data structure.
There was previously a mismatch between the default reported number of qubits the Aer backend objects would say were supported and the the maximum number of qubits the simulator would actually run. This was due to a mismatch between the Python code used for calculating the max number of qubits and the C++ code used for a runtime check for the max number of qubits based on the available memory. This has been correct so by default now Aer backends will allow running circuits that can fit in all the available system memory. Fixes #1114

No change

Ignis 0.5.2¶

No change

Aqua 0.8.2¶

No change

IBM Q Provider 0.12.0¶

Prelude¶

qiskit.providers.ibmq.IBMQBackend.run() method now takes one or more QuantumCircuit or Schedule. Use of QasmQobj and PulseQobj is now deprecated. Runtime configuration options, such as the number of shots, can be set via either the run() method, or the qiskit.providers.ibmq.IBMQBackend.set_options() method. The former is used as a one-time setting for the job, and the latter for all jobs sent to the backend. If an option is set in both places, the value set in run() takes precedence.
IBM Quantum credentials are now loaded only from sections of the qiskitrc file that start with “ibmq”.

New Features¶

Python 3.9 support has been added in this release. You can now run Qiskit IBMQ provider using Python 3.9.
qiskit.providers.ibmq.AccountProvider.backends() now has a new parameter min_num_qubits that allows you to filter by the minimum number of qubits.

qiskit.providers.ibmq.IBMQBackend.run() method now takes one or more QuantumCircuit or Schedule. Runtime configuration options, such as the number of shots, can be set via either the run() method, or the qiskit.providers.ibmq.IBMQBackend.set_options() method. The former is used as a one-time setting for the job, and the latter for all jobs sent to the backend. If an option is set in both places, the value set in run() takes precedence. For example:

from qiskit import IBMQ, transpile
from qiskit.test.reference_circuits import ReferenceCircuits

provider = IBMQ.load_account()
backend = provider.get_backend('ibmq_vigo')
circuits = transpile(ReferenceCircuits.bell(), backend=backend)
default_shots = backend.options.shots  # Returns the backend default of 1024 shots.
backend.set_options(shots=2048)        # All jobs will now have use 2048 shots.
backend.run(circuits)                  # This runs with 2048 shots.
backend.run(circuits, shots=8192)      # This runs with 8192 shots.
backend.run(circuits)                  # This again runs with 2048 shots.

qiskit.providers.ibmq.experiment.Experiment now has three additional attributes, hub, group, and project, that identify the provider used to create the experiment.
You can now assign an experiment_id to a job when submitting it using qiskit.providers.ibmq.IBMQBackend.run(). You can use this new field to group together a collection of jobs that belong to the same experiment. The qiskit.providers.ibmq.IBMQBackendService.jobs() method was also updated to allow filtering by experiment_id.
qiskit.providers.ibmq.experiment.Experiment now has two additional attributes:
- share_level: The level at which the experiment is shared which determines who can see it when listing experiments. This can be updated.
- owner: The ID of the user that uploaded the experiment. This is set by the server and cannot be updated.
The method qiskit.providers.ibmq.experimentservice.ExperimentService.experiments() now accepts hub, group, and project as filtering keywords.
Methods qiskit.providers.ibmq.experiment.ExperimentService.experiments() and qiskit.providers.ibmq.experiment.ExperimentService.analysis_results() now support a limit parameter that allows you to limit the number of experiments and analysis results returned.
The method qiskit.providers.ibmq.experimentservice.ExperimentService.experiments() now accepts exclude_mine and mine_only as filtering keywords.
The method qiskit.providers.ibmq.experimentservice.ExperimentService.experiments() now accepts exclude_public and public_only as filtering keywords.
qiskit.providers.ibmq.managed.IBMQJobManager.run() now accepts a single QuantumCircuit or Schedule in addition to a list of them.
The least_busy() function now skips backends that are operational but paused, meaning they are accepting but not processing jobs.
You can now pickle an IBMQJob instance, as long as it doesn’t contain custom data that is not picklable (e.g. in Qobj header).
You can now use the two new methods, qiskit.providers.ibmq.AccountProvider.services() and qiskit.providers.ibmq.AccountProvider.service() to find out what services are available to your account and get an instance of a particular service.
The qiskit.providers.ibmq.IBMQBackend.reservations() method now always returns the reservation scheduling modes even for reservations that you don’t own.

Upgrade Notes¶

A number of previously deprecated methods and features have been removed, including:
- qiskit.providers.ibmq.job.IBMQJob.to_dict()
- qiskit.providers.ibmq.job.IBMQJob.from_dict()
- Qconfig.py support
- Use of proxy URLs that do not include protocols
A new parameter, limit is now the first parameter for both qiskit.providers.ibmq.experiment.ExperimentService.experiments() and qiskit.providers.ibmq.experiment.ExperimentService.analysis_results() methods. This limit has a default value of 10, meaning by deafult only 10 experiments and analysis results will be returned.
IBM Quantum credentials are now loaded only from sections of the qiskitrc file that start with “ibmq”. This allows the qiskitrc file to be used for other functionality.

Deprecation Notes¶

Use of QasmQobj and PulseQobj in the qiskit.providers.ibmq.IBMQBackend.run() method is now deprecated. QuantumCircuit and Schedule should now be used instead.
The backends attribute of qiskit.providers.ibmq.AccountProvider has been renamed to backend (sigular). For backward compatibility, you can continue to use backends, but it is deprecated and will be removed in a future release. The qiskit.providers.ibmq.AccountProvider.backends() method remains unchanged. For example:
```
backend = provider.backend.ibmq_vigo   # This is the new syntax.
backend = provider.backends.ibmq_vigo  # This is deprecated.
backends = provider.backends()         # This continues to work as before.
```
Setting of the IBMQJob client_version attribute has been deprecated. You can, however, continue to read the value of attribute.
« The validate_qobj keyword in qiskit.providers.ibmq.IBMQBackend.run() is deprecated and will be removed in a future release. If you’re relying on this schema validation you should pull the schemas from the Qiskit/ibmq-schemas and directly validate your payloads with that.

Bug Fixes¶

Fixes the issue wherein a job could be left in the CREATING state if job submit fails half-way through.
Fixes the issue wherein using Jupyter backend widget would fail if the backend’s basis gates do not include the traditional u1, u2, and u3. Fixes #844
Fixes the infinite loop raised when passing an IBMQRandomService instance to a child process.
Fixes the issue wherein a TypeError is raised if the server returns an error code but the response data is not in the expected format.

Qiskit 0.23.6¶

Terra 0.16.4¶

No change

Aer 0.7.5¶

Prelude¶

This release is a bugfix release that fixes compatibility in the precompiled binary wheel packages with numpy versions < 1.20.0. The previous release 0.7.4 was building the binaries in a way that would require numpy 1.20.0 which has been resolved now, so the precompiled binary wheel packages will work with any numpy compatible version.

Ignis 0.5.2¶

No change

Aqua 0.8.2¶

No change

IBM Q Provider 0.11.1¶

No change

Qiskit 0.23.5¶

Terra 0.16.4¶

Prelude¶

This release is a bugfix release that primarily fixes compatibility with numpy 1.20.0. This numpy release deprecated their local aliases for Python’s numeric types (np.int -> int, np.float -> float, etc.) and the usage of these aliases in Qiskit resulted in a large number of deprecation warnings being emitted. This release fixes this so you can run Qiskit with numpy 1.20.0 without those deprecation warnings.

Aer 0.7.4¶

Bug Fixes¶

Fixes compatibility with numpy 1.20.0. This numpy release deprecated their local aliases for Python’s numeric types (np.int -> int, np.float -> float, etc.) and the usage of these aliases in Qiskit Aer resulted in a large number of deprecation warnings being emitted. This release fixes this so you can run Qiskit Aer with numpy 1.20.0 without those deprecation warnings.

Ignis 0.5.2¶

Prelude¶

This release is a bugfix release that primarily fixes compatibility with numpy 1.20.0. It is also the first release to include support for Python 3.9. Earlier releases (including 0.5.0 and 0.5.1) worked with Python 3.9 but did not indicate this in the package metadata, and there was no upstream testing for those releases. This release fixes that and was tested on Python 3.9 (in addition to 3.6, 3.7, and 3.8).

Bug Fixes¶

networkx is explicitly listed as a dependency now. It previously was an implicit dependency as it was required for the qiskit.ignis.verification.topological_codes module but was not correctly listed as a depdendency as qiskit-terra also requires networkx and is also a depdency of ignis so it would always be installed in practice. However, it is necessary to list it as a requirement for future releases of qiskit-terra that will not require networkx. It’s also important to correctly list the dependencies of ignis in case there were a future incompatibility between version requirements.

Aqua 0.8.2¶

IBM Q Provider 0.11.1¶

No change

Qiskit 0.23.4¶

Terra 0.16.3¶

Bug Fixes¶

Fixed an issue introduced in 0.16.2 that would cause errors when running transpile() on a circuit with a series of 1 qubit gates and a non-gate instruction that only operates on a qubit (e.g. Reset). Fixes #5736

Aer 0.7.3¶

No change

Ignis 0.5.1¶

No change

Aqua 0.8.1¶

No change

IBM Q Provider 0.11.1¶

No change

Qiskit 0.23.3¶

Terra 0.16.2¶

New Features¶

Python 3.9 support has been added in this release. You can now run Qiskit Terra using Python 3.9.

Upgrade Notes¶

The class MCXGrayCode will now create a C3XGate if num_ctrl_qubits is 3 and a C4XGate if num_ctrl_qubits is 4. This is in addition to the previous functionality where for any of the modes of the :class:”qiskit.library.standard_gates.x.MCXGate`, if num_ctrl_bits is 1, a CXGate is created, and if 2, a CCXGate is created.

Bug Fixes¶

Pulse Delay instructions are now explicitly assembled as PulseQobjInstruction objects included in the PulseQobj output from assemble().

Previously, we could ignore Delay instructions in a Schedule as part of assemble() as the time was explicit in the PulseQobj objects. But, now with pulse gates, there are situations where we can schedule ONLY a delay, and not including the delay itself would remove the delay.
Circuits with custom gate calibrations can now be scheduled with the transpiler without explicitly providing the durations of each circuit calibration.
The BasisTranslator and Unroller passes, in some cases, had not been preserving the global phase of the circuit under transpilation. This has been fixed.
A bug in qiskit.pulse.builder.frequency_offset() where when compensate_phase was set a factor of \(2\pi\) was missing from the appended phase.
Fix the global phase of the output of the QuantumCircuit method repeat(). If a circuit with global phase is appended to another circuit, the global phase is currently not propagated. Simulators rely on this, since the phase otherwise gets applied multiple times. This sets the global phase of repeat() to 0 before appending the repeated circuit instead of multiplying the existing phase times the number of repetitions.
Fixes bug in SparsePauliOp where multiplying by a certain non Python builtin Numpy scalar types returned incorrect values. Fixes #5408
The definition of the Hellinger fidelity from has been corrected from the previous defition of \(1-H(P,Q)\) to \([1-H(P,Q)^2]^2\) so that it is equal to the quantum state fidelity of P, Q as diagonal density matrices.
Reduce the number of CX gates in the decomposition of the 3-controlled X gate, C3XGate. Compiled and optimized in the U CX basis, now only 14 CX and 16 U gates are used instead of 20 and 22, respectively.
Fixes the issue wherein using Jupyter backend widget or qiskit.tools.backend_monitor() would fail if the backend’s basis gates do not include the traditional u1, u2, and u3.
When running qiskit.compiler.transpile() on a list of circuits with a single element, the function used to return a circuit instead of a list. Now, when qiskit.compiler.transpile() is called with a list, it will return a list even if that list has a single element. See #5260.
```
from qiskit import *

qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()

transpiled = transpile([qc])
print(type(transpiled), len(transpiled))
```
```
<class 'list'> 1
```

Aer 0.7.3¶

New Features¶

Python 3.9 support has been added in this release. You can now run Qiskit Aer using Python 3.9 without building from source.

Bug Fixes¶

Fixes issue with setting QasmSimulator basis gates when using "method" and "noise_model" options together, and when using them with a simulator constructed using from_backend(). Now the listed basis gates will be the intersection of gates supported by the backend configuration, simulation method, and noise model basis gates. If the intersection of the noise model basis gates and simulator basis gates is empty a warning will be logged.
Fixes a bug that resulted in c_if not working when the width of the conditional register was greater than 64. See #1077.
Fixes bug in from_backend() and from_backend() where basis_gates was set incorrectly for IBMQ devices with basis gate set ['id', 'rz', 'sx', 'x', 'cx']. Now the noise model will always have the same basis gates as the backend basis gates regardless of whether those instructions have errors in the noise model or not.
Fixes a bug when applying truncation in the matrix product state method of the QasmSimulator.

Ignis 0.5.1¶

No change

Aqua 0.8.1¶

No change

IBM Q Provider 0.11.1¶

No change

Qiskit 0.23.2¶

Terra 0.16.1¶

No change

Aer 0.7.2¶

New Features¶

Add the CMake flag DISABLE_CONAN (default=``OFF``)s. When installing from source, setting this to ON allows bypassing the Conan package manager to find libraries that are already installed on your system. This is also available as an environment variable DISABLE_CONAN, which takes precedence over the CMake flag. This is not the official procedure to build AER. Thus, the user is responsible of providing all needed libraries and corresponding files to make them findable to CMake.

Bug Fixes¶

Fixes a bug with nested OpenMP flag was being set to true when it shouldn’t be.

Ignis 0.5.1¶

No change

Aqua 0.8.1¶

No change

IBM Q Provider 0.11.1¶

No change

Qiskit 0.23.1¶

Terra 0.16.1¶

Bug Fixes¶

Fixed an issue where an error was thrown in execute for valid circuits built with delays.
The QASM definition of “c4x” in qelib1.inc has been corrected to match the standard library definition for C4XGate.
Fixes a bug in subtraction for quantum channels \(A - B\) where \(B\) was an Operator object. Negation was being applied to the matrix in the Operator representation which is not equivalent to negation in the quantum channel representation.
Changes the way _evolve_instruction() access qubits to handle the case of an instruction with multiple registers.

Aer 0.7.1¶

Upgrade Notes¶

The minimum cmake version to build qiskit-aer has increased from 3.6 to 3.8. This change was necessary to enable fixing GPU version builds that support running on x86_64 CPUs lacking AVX2 instructions.

Bug Fixes¶

qiskit-aer with GPU support will now work on systems with x86_64 CPUs lacking AVX2 instructions. Previously, the GPU package would only run if the AVX2 instructions were available. Fixes #1023
Fixes bug with AerProvider where options set on the returned backends using set_options() were stored in the provider and would persist for subsequent calls to get_backend() for the same named backend. Now every call to and backends() returns a new instance of the simulator backend that can be configured.
Fixes bug in the error message returned when a circuit contains unsupported simulator instructions. Previously some supported instructions were also being listed in the error message along with the unsupported instructions.
Fix bug where the « sx »` gate SXGate was not listed as a supported gate in the C++ code, in StateOpSet of matrix_product_state.hp.
Fix bug where "csx", "cu2", "cu3" were incorrectly listed as supported basis gates for the "density_matrix" method of the QasmSimulator.
In MPS, apply_kraus was operating directly on the input bits in the parameter qubits, instead of on the internal qubits. In the MPS algorithm, the qubits are constantly moving around so all operations should be applied to the internal qubits.
When invoking MPS::sample_measure, we need to first sort the qubits to the default ordering because this is the assumption in qasm_controller.This is done by invoking the method move_all_qubits_to_sorted_ordering. It was correct in sample_measure_using_apply_measure, but missing in sample_measure_using_probabilities.

Ignis 0.5.1¶

Bug Fixes¶

Fix the "auto" method of the TomographyFitter, StateTomographyFitter, and ProcessTomographyFitter to only use "cvx" if CVXPY is installed and a third-party SDP solver other than SCS is available. This is because the SCS solver has lower accuracy than other solver methods and often returns a density matrix or Choi-matrix that is not completely-positive and fails validation when used with the qiskit.quantum_info.state_fidelity() or qiskit.quantum_info.process_fidelity() functions.

Aqua 0.8.1¶

0.8.1¶

New Features¶

A new algorithm has been added: the Born Openheimer Potential Energy surface for the calculation of potential energy surface along different degrees of freedom of the molecule. The algorithm is called BOPESSampler. It further provides functionalities of fitting the potential energy surface to an analytic function of predefined potentials.some details.

Critical Issues¶

Be aware that initial_state parameter in QAOA has now different implementation as a result of a bug fix. The previous implementation wrongly mixed the user provided initial_state with Hadamard gates. The issue is fixed now. No attention needed if your code does not make use of the user provided initial_state parameter.

Bug Fixes¶

optimize_svm method of qp_solver would sometimes fail resulting in an error like this ValueError: cannot reshape array of size 1 into shape (200,1) This addresses the issue by adding an L2 norm parameter, lambda2, which defaults to 0.001 but can be changed via the QSVM algorithm, as needed, to facilitate convergence.
A method one_letter_symbol has been removed from the VarType in the latest build of DOCplex making Aqua incompatible with this version. So instead of using this method an explicit type check of variable types has been introduced in the Aqua optimization module.
:meth`~qiskit.aqua.operators.state_fns.DictStateFn.sample()` could only handle real amplitudes, but it is fixed to handle complex amplitudes. #1311 <https://github.com/Qiskit/qiskit-aqua/issues/1311> for more details.
Trotter class did not use the reps argument in constructor. #1317 <https://github.com/Qiskit/qiskit-aqua/issues/1317> for more details.
Raise an AquaError if :class`qiskit.aqua.operators.converters.CircuitSampler` samples an empty operator. #1321 <https://github.com/Qiskit/qiskit-aqua/issues/1321> for more details.
to_opflow() returns a correct operator when coefficients are complex numbers. #1381 <https://github.com/Qiskit/qiskit-aqua/issues/1381> for more details.
Let backend simulators validate NoiseModel support instead of restricting to Aer only in QuantumInstance.
Correctly handle PassManager on QuantumInstance transpile method by calling its run method if it exists.
A bug that mixes custom initial_state in QAOA with Hadamard gates has been fixed. This doesn’t change functionality of QAOA if no initial_state is provided by the user. Attention should be taken if your implementation uses QAOA with cusom initial_state parameter as the optimization results might differ.
Previously, setting seed_simulator=0 in the QuantumInstance did not set any seed. This was only affecting the value 0. This has been fixed.

IBM Q Provider 0.11.1¶

New Features¶

qiskit.providers.ibmq.experiment.Experiment now has three additional attributes, hub, group, and project, that identify the provider used to create the experiment.
Methods qiskit.providers.ibmq.experiment.ExperimentService.experiments() and qiskit.providers.ibmq.experiment.ExperimentService.analysis_results() now support a limit parameter that allows you to limit the number of experiments and analysis results returned.

Upgrade Notes¶

A new parameter, limit is now the first parameter for both qiskit.providers.ibmq.experiment.ExperimentService.experiments() and qiskit.providers.ibmq.experiment.ExperimentService.analysis_results() methods. This limit has a default value of 10, meaning by deafult only 10 experiments and analysis results will be returned.

Bug Fixes¶

Fixes the issue wherein a job could be left in the CREATING state if job submit fails half-way through.
Fixes the infinite loop raised when passing an IBMQRandomService instance to a child process.

Qiskit 0.23.0¶

Terra 0.16.0¶

Prelude¶

The 0.16.0 release includes several new features and bug fixes. The major features in this release are the following:

Introduction of scheduled circuits, where delays can be used to control the timing and alignment of operations in the circuit.
Compilation of quantum circuits from classical functions, such as oracles.
Ability to compile and optimize single qubit rotations over different Euler basis as well as the phase + square-root(X) basis (i.e. ['p', 'sx']), which will replace the older IBM Quantum basis of ['u1', 'u2', 'u3'].
Tracking of global_phase() on the QuantumCircuit class has been extended through the transpiler, quantum_info, and assembler modules, as well as the BasicAer and Aer simulators. Unitary and state vector simulations will now return global phase-correct unitary matrices and state vectors.

Also of particular importance for this release is that Python 3.5 is no longer supported. If you are using Qiskit Terra with Python 3.5, the 0.15.2 release is that last version which will work.

New Features¶

Global R gates have been added to qiskit.circuit.library. This includes the global R gate (GR), global Rx (GRX) and global Ry (GRY) gates which are derived from the GR gate, and global Rz ( GRZ) that is defined in a similar way to the GR gates. The global R gates are defined on a number of qubits simultaneously, and act as a direct sum of R gates on each qubit.

For example:
```
from qiskit import QuantumCircuit, QuantumRegister
import numpy as np

num_qubits = 3
qr = QuantumRegister(num_qubits)
qc = QuantumCircuit(qr)

qc.compose(GR(num_qubits, theta=np.pi/3, phi=2*np.pi/3), inplace=True)
```
will create a QuantumCircuit on a QuantumRegister of 3 qubits and perform a RGate of an angle \(\theta = \frac{\pi}{3}\) about an axis in the xy-plane of the Bloch spheres that makes an angle of \(\phi = \frac{2\pi}{3}\) with the x-axis on each qubit.
A new color scheme, iqx, has been added to the mpl backend for the circuit drawer qiskit.visualization.circuit_drawer() and qiskit.circuit.QuantumCircuit.draw(). This uses the same color scheme as the Circuit Composer on the IBM Quantum Experience website. There are now 3 available color schemes - default, iqx, and bw.

There are two ways to select a color scheme. The first is to use a user config file, by default in the ~/.qiskit directory, in the file settings.conf under the [Default] heading, a user can enter circuit_mpl_style = iqx to select the iqx color scheme.

The second way is to add {'name': 'iqx'} to the style kwarg to the QuantumCircuit.draw method or to the circuit_drawer function. The second way will override the setting in the settings.conf file. For example:
from qiskit.circuit import QuantumCircuit circuit = QuantumCircuit(2) circuit.h(0) circuit.cx(0, 1) circuit.measure_all() circuit.draw('mpl', style={'name': 'iqx'})
In the style kwarg for the the circuit drawer qiskit.visualization.circuit_drawer() and qiskit.circuit.QuantumCircuit.draw() the displaycolor field with the mpl backend now allows for entering both the gate color and the text color for each gate type in the form (gate_color, text_color). This allows the use of light and dark gate colors with contrasting text colors. Users can still set only the gate color, in which case the gatetextcolor field will be used. Gate colors can be set in the style dict for any number of gate types, from one to the entire displaycolor dict. For example:
from qiskit.circuit import QuantumCircuit circuit = QuantumCircuit(1) circuit.h(0) style_dict = {'displaycolor': {'h': ('#FA74A6', '#000000')}} circuit.draw('mpl', style=style_dict)
or
style_dict = {'displaycolor': {'h': '#FA74A6'}} circuit.draw('mpl', style=style_dict)
Two alignment contexts are added to the pulse builder (qiskit.pulse.builder) to facilitate writing a repeated pulse sequence with delays.
- qiskit.pulse.builder.align_equispaced() inserts delays with equivalent length in between pulse schedules within the context.
- qiskit.pulse.builder.align_func() offers more advanced control of pulse position. This context takes a callable that calculates a fractional coordinate of i-th pulse and aligns pulses within the context. This makes coding of dynamical decoupling easy.
A rep_delay parameter has been added to the QasmQobj class under the run configuration, QasmQobjConfig. This parameter is used to denote the time between program executions. It must be chosen from the backend range given by the BackendConfiguration method rep_delay_range(). If a value is not provided a backend default, qiskit.providers.models.BackendConfiguration.default_rep_delay, will be used. rep_delay will only work on backends which allow for dynamic repetition time. This is can be checked with the BackendConfiguration property dynamic_reprate_enabled.
The qobj_schema.json JSON Schema file in qiskit.schemas has been updated to include the rep_delay as an optional configuration property for QASM Qobjs.
The backend_configuration_schema.json JSON Schema file in qiskit.schemas has been updated to include dynamic_reprate_enabled, rep_delay_range and default_rep_delay as optional properties for a QASM backend configuration payload.
A new optimization pass, qiskit.transpiler.passes.TemplateOptimization has been added to the transpiler. This pass applies a template matching algorithm described in arXiv:1909.05270 that replaces all compatible maximal matches in the circuit.

To implement this new transpiler pass a new module, template_circuits, was added to the circuit library (qiskit.circuit.library). This new module contains all the Toffoli circuit templates used in the TemplateOptimization.

This new pass is not currently included in the preset pass managers (qiskit.transpiler.preset_passmanagers), to use it you will need to create a custom PassManager.
A new version of the providers interface has been added. This new interface, which can be found in qiskit.providers, provides a new versioning mechanism that will enable changes to the interface to happen in a compatible manner over time. The new interface should be simple to migrate existing providers, as it is mostly identical except for the explicit versioning.

Besides having explicitly versioned abstract classes the key changes for the new interface are that the BackendV1 method run() can now take a QuantumCircuit or Schedule object as inputs instead of Qobj objects. To go along with that options are now part of a backend class so that users can configure run time options when running with a circuit. The final change is that qiskit.providers.JobV1 can now be synchronous or asynchronous, the exact configuration and method for configuring this is up to the provider, but there are interface hook points to make it explicit which execution model a job is running under in the JobV1 abstract class.
A new kwarg, inplace, has been added to the function qiskit.result.marginal_counts(). This kwarg is used to control whether the contents are marginalized in place or a new copy is returned, for Result object input. This parameter does not have any effect for an input dict or Counts object.

An initial version of a classical function compiler, qiskit.circuit.classicalfunction, has been added. This enables compiling typed python functions (operating only on bits of type Int1 at the moment) into QuantumCircuit objects. For example:

from qiskit.circuit import classical_function, Int1

@classical_function
def grover_oracle(a: Int1, b: Int1, c: Int1, d: Int1) -> Int1:
     x = not a and b
     y = d and not c
     z = not x or y
     return z

quantum_circuit = grover_oracle.synth()
quantum_circuit.draw()

                                   
q_0: ──■────■────■────o────────────
       │    │    │    │            
q_1: ──o────o────┼────┼────■────■──
       │    │    │    │    │    │  
q_2: ──o────■────o────┼────■────┼──
       │    │    │    │    │    │  
q_3: ──o────┼────■────┼────■────o──
     ┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐
q_4: ┤ X ├┤ X ├┤ X ├┤ X ├┤ X ├┤ X ├
     └───┘└───┘└───┘└───┘└───┘└───┘

The parameter registerless=False in the qiskit.circuit.classicalfunction.ClassicalFunction method synth() creates a circuit with registers refering to the parameter names. For example:

quantum_circuit = grover_oracle.synth(registerless=False)
quantum_circuit.draw()

                                        
     d_0: ──■────■────■────o────────────
            │    │    │    │            
     c_0: ──o────o────┼────┼────■────■──
            │    │    │    │    │    │  
     b_0: ──o────■────o────┼────■────┼──
            │    │    │    │    │    │  
     a_0: ──o────┼────■────┼────■────o──
          ┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐
return_0: ┤ X ├┤ X ├┤ X ├┤ X ├┤ X ├┤ X ├
          └───┘└───┘└───┘└───┘└───┘└───┘

A decorated classical function can be used the same way as any other quantum gate when appending it to a circuit.

circuit = QuantumCircuit(5)
circuit.append(grover_oracle, range(5))
circuit.draw()

     ┌────────────────┐
q_0: ┤0               ├
     │                │
q_1: ┤1               ├
     │                │
q_2: ┤2 GROVER_ORACLE ├
     │                │
q_3: ┤3               ├
     │                │
q_4: ┤4               ├
     └────────────────┘

The GROVER_ORACLE gate is synthesized when its decomposition is required.

circuit.decompose().draw()

                                   
q_0: ──■────■────■────o────────────
       │    │    │    │            
q_1: ──o────o────┼────┼────■────■──
       │    │    │    │    │    │  
q_2: ──o────■────o────┼────■────┼──
       │    │    │    │    │    │  
q_3: ──o────┼────■────┼────■────o──
     ┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐┌─┴─┐
q_4: ┤ X ├┤ X ├┤ X ├┤ X ├┤ X ├┤ X ├
     └───┘└───┘└───┘└───┘└───┘└───┘

The feature requires tweedledum, a library for synthesizing quantum circuits, that can be installed via pip with pip install tweedledum.

A new class qiskit.circuit.Delay for representing a delay instruction in a circuit has been added. A new method delay() is now available for easily appending delays to circuits. This makes it possible to describe timing-sensitive experiments (e.g. T1/T2 experiment) in the circuit level.

from qiskit import QuantumCircuit

qc = QuantumCircuit(1, 1)
qc.delay(500, 0, unit='ns')
qc.measure(0, 0)

qc.draw()

     ┌────────────────┐┌─┐
q_0: ┤ DELAY(500[ns]) ├┤M├
     └────────────────┘└╥┘
c: 1/═══════════════════╩═
                        0

A new argument scheduling_method for qiskit.compiler.transpile() has been added. It is required when transpiling circuits with delays. If scheduling_method is specified, the transpiler returns a scheduled circuit such that all idle times in it are padded with delays (i.e. start time of each instruction is uniquely determined). This makes it possible to see how scheduled instructions (gates) look in the circuit level.

from qiskit import QuantumCircuit, transpile
from qiskit.test.mock.backends import FakeAthens

qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)

scheduled_circuit = transpile(qc, backend=FakeAthens(), scheduling_method="alap")
print("Duration in dt:", scheduled_circuit.duration)
scheduled_circuit.draw(idle_wires=False)

Duration in dt: 2016

            ┌─────────┐    ┌────┐┌─────────┐     
q_0 -> 0 ───┤ RZ(π/2) ├────┤ √X ├┤ RZ(π/2) ├──■──
         ┌──┴─────────┴───┐└────┘└─────────┘┌─┴─┐
q_1 -> 1 ┤ DELAY(160[dt]) ├─────────────────┤ X ├
         └────────────────┘                 └───┘

See also timeline_drawer() for the best visualization of scheduled circuits.

A new fuction qiskit.compiler.sequence() has been also added so that we can convert a scheduled circuit into a Schedule to make it executable on a pulse-enabled backend.
```
from qiskit.compiler import sequence

sched = sequence(scheduled_circuit, pulse_enabled_backend)
```

The schedule() has been updated so that it can schedule circuits with delays. Now there are two paths to schedule a circuit with delay:

qc = QuantumCircuit(1, 1)
qc.h(0)
qc.delay(500, 0, unit='ns')
qc.h(0)
qc.measure(0, 0)

sched_path1 = schedule(qc.decompose(), backend)
sched_path2 = sequence(transpile(qc, backend, scheduling_method='alap'), backend)
assert pad(sched_path1) == sched_path2

Refer to the release notes and documentation for transpile() and sequence() for the details on the other path.

Added the GroverOperator to the circuit library (qiskit.circuit.library) to construct the Grover operator used in Grover’s search algorithm and Quantum Amplitude Amplification/Estimation. Provided with an oracle in form of a circuit, GroverOperator creates the textbook Grover operator. To generalize this for amplitude amplification and use a generic operator instead of Hadamard gates as state preparation, the state_in argument can be used.
The InstructionScheduleMap methods get() and pop() methods now take ParameterExpression instances in addition to numerical values for schedule generator parameters. If the generator is a function, expressions may be bound before or within the function call. If the generator is a ParametrizedSchedule, expressions must be bound before the schedule itself is bound/called.
A new class LinearAmplitudeFunction was added to the circuit library (qiskit.circuit.library) for mapping (piecewise) linear functions on qubit amplitudes,

\[F|x\rangle |0\rangle = \sqrt{1 - f(x)}|x\rangle |0\rangle + \sqrt{f(x)}|x\rangle |1\rangle\]

The mapping is based on a controlled Pauli Y-rotations and a Taylor approximation, as described in https://arxiv.org/abs/1806.06893. This circuit can be used to compute expectation values of linear functions using the quantum amplitude estimation algorithm.
The new jupyter magic monospaced_output has been added to the qiskit.tools.jupyter module. This magic sets the Jupyter notebook output font to « Courier New », when possible. When used this fonts returns text circuit drawings that are better aligned.
```
import qiskit.tools.jupyter
%monospaced_output
```
A new transpiler pass, Optimize1qGatesDecomposition, has been added. This transpiler pass is an alternative to the existing Optimize1qGates that uses the OneQubitEulerDecomposer class to decompose and simplify a chain of single qubit gates. This method is compatible with any basis set, while Optimize1qGates only works for u1, u2, and u3. The default pass managers for optimization_level 1, 2, and 3 have been updated to use this new pass if the basis set doesn’t include u1, u2, or u3.
The OneQubitEulerDecomposer now supports two new basis, 'PSX' and 'U'. These can be specified with the basis kwarg on the constructor. This will decompose the matrix into a circuit using PGate and SXGate for 'PSX', and UGate for 'U'.

A new method remove() has been added to the qiskit.transpiler.PassManager class. This method enables removing a pass from a PassManager instance. It works on indexes, similar to replace(). For example, to remove the RemoveResetInZeroState pass from the pass manager used at optimization level 1:

from qiskit.transpiler.preset_passmanagers import level_1_pass_manager
from qiskit.transpiler.passmanager_config import PassManagerConfig

pm = level_1_pass_manager(PassManagerConfig())
pm.draw()

[0] FlowLinear: UnrollCustomDefinitions, BasisTranslator
[1] FlowLinear: RemoveResetInZeroState
[2] DoWhile: Depth, FixedPoint, Optimize1qGates, CXCancellation

The stage [1] with RemoveResetInZeroState can be removed like this:

pass_manager.remove(1)
pass_manager.draw()

[0] FlowLinear: UnrollCustomDefinitions, BasisTranslator
[1] DoWhile: Depth, FixedPoint, Optimize1qGates, CXCancellation

Several classes to load probability distributions into qubit amplitudes; UniformDistribution, NormalDistribution, and LogNormalDistribution were added to the circuit library (qiskit.circuit.library). The normal and log-normal distribution support both univariate and multivariate distributions. These circuits are central to applications in finance where quantum amplitude estimation is used.
Support for pulse gates has been added to the QuantumCircuit class. This enables a QuantumCircuit to override (for basis gates) or specify (for standard and custom gates) a definition of a Gate operation in terms of time-ordered signals across hardware channels. In other words, it enables the option to provide pulse-level custom gate calibrations.

The circuits are built exactly as before. For example:
```
from qiskit import pulse
from qiskit.circuit import QuantumCircuit, Gate

class RxGate(Gate):
    def __init__(self, theta):
        super().__init__('rxtheta', 1, [theta])

circ = QuantumCircuit(1)
circ.h(0)
circ.append(RxGate(3.14), [0])
```
Then, the calibration for the gate can be registered using the QuantumCircuit method add_calibration() which takes a Schedule definition as well as the qubits and parameters that it is defined for:
```
# Define the gate implementation as a schedule
with pulse.build() as custom_h_schedule:
    pulse.play(pulse.library.Drag(...), pulse.DriveChannel(0))

with pulse.build() as q1_x180:
    pulse.play(pulse.library.Gaussian(...), pulse.DriveChannel(1))

# Register the schedule to the gate
circ.add_calibration('h', [0], custom_h_schedule)  # or gate.name string to register
circ.add_calibration(RxGate(3.14), [0], q1_x180)   # Can accept gate
```
Previously, this functionality could only be used through complete Pulse Schedules. Additionally, circuits can now be submitted to backends with your custom definitions (dependent on backend support).

Circuits with pulse gates can still be lowered to a Schedule by using the schedule() function.

The calibrated gate can also be transpiled using the regular transpilation process:
```
transpiled_circuit = transpile(circ, backend)
```
The transpiled circuit will leave the calibrated gates on the same qubit as the original circuit and will not unroll them to the basis gates.

Support for disassembly of PulseQobj objects has been added to the qiskit.assembler.disassemble() function. For example:

from qiskit import pulse
from qiskit.assembler.disassemble import disassemble
from qiskit.compiler.assemble import assemble
from qiskit.test.mock import FakeOpenPulse2Q

backend = FakeOpenPulse2Q()

d0 = pulse.DriveChannel(0)
d1 = pulse.DriveChannel(1)
with pulse.build(backend) as sched:
    with pulse.align_right():
        pulse.play(pulse.library.Constant(10, 1.0), d0)
        pulse.shift_phase(3.11, d0)
        pulse.measure_all()

qobj = assemble(sched, backend=backend, shots=512)
scheds, run_config, header = disassemble(qobj)

A new kwarg, coord_type has been added to qiskit.visualization.plot_bloch_vector(). This kwarg enables changing the coordinate system used for the input parameter that describes the positioning of the vector on the Bloch sphere in the generated visualization. There are 2 supported values for this new kwarg, 'cartesian' (the default value) and 'spherical'. If the coord_type kwarg is set to 'spherical' the list of parameters taken in are of the form [r, theta, phi] where r is the radius, theta is the inclination from +z direction, and phi is the azimuth from +x direction. For example:
from numpy import pi from qiskit.visualization import plot_bloch_vector x = 0 y = 0 z = 1 r = 1 theta = pi phi = 0 # Cartesian coordinates, where (x,y,z) are cartesian coordinates # for bloch vector plot_bloch_vector([x,y,z])
plot_bloch_vector([x,y,z], coord_type="cartesian") # Same as line above
# Spherical coordinates, where (r,theta,phi) are spherical coordinates # for bloch vector plot_bloch_vector([r, theta, phi], coord_type="spherical")

Pulse Schedule objects now support using ParameterExpression objects for parameters.

For example:

from qiskit.circuit import Parameter
from qiskit import pulse

alpha = Parameter('⍺')
phi = Parameter('ϕ')
qubit = Parameter('q')
amp = Parameter('amp')

schedule = pulse.Schedule()
schedule += SetFrequency(alpha, DriveChannel(qubit))
schedule += ShiftPhase(phi, DriveChannel(qubit))
schedule += Play(Gaussian(duration=128, sigma=4, amp=amp),
                 DriveChannel(qubit))
schedule += ShiftPhase(-phi, DriveChannel(qubit))

Parameter assignment is done via the assign_parameters() method:

schedule.assign_parameters({alpha: 4.5e9, phi: 1.57,
                            qubit: 0, amp: 0.2})

Expressions and partial assignment also work, such as:

beta = Parameter('b')
schedule += SetFrequency(alpha + beta, DriveChannel(0))
schedule.assign_parameters({alpha: 4.5e9})
schedule.assign_parameters({beta: phi / 6.28})

A new visualization function timeline_drawer() was added to the qiskit.visualization module.

For example:

from qiskit.visualization import timeline_drawer
from qiskit import QuantumCircuit, transpile
from qiskit.test.mock import FakeAthens

qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0,1)
timeline_drawer(transpile(qc, FakeAthens(), scheduling_method='alap'))

Upgrade Notes¶

Type checking for the params kwarg of the constructor for the Gate class and its subclasses has been changed. Previously all Gate parameters had to be in a set of allowed types defined in the Instruction class. Now a new method, validate_parameter() is used to determine if a parameter type is valid or not. The definition of this method in a subclass will take priority over its parent. For example, UnitaryGate accepts a parameter of the type numpy.ndarray and defines a custom validate_parameter() method that returns the parameter if it’s an numpy.ndarray. This takes priority over the function defined in its parent class Gate. If UnitaryGate were to be used as parent for a new class, this validate_parameter method would be used unless the new child class defines its own method.
The previously deprecated methods, arguments, and properties named n_qubits and numberofqubits have been removed. These were deprecated in the 0.13.0 release. The full set of changes are:

Class

Old

New

QuantumCircuit

n_qubits

num_qubits

Pauli

numberofqubits

num_qubits

Function

Old Argument

New Argument

qiskit.circuit.random.random_circuit()

n_qubits

num_qubits

qiskit.circuit.library.MSGate

n_qubits

num_qubits
Inserting a parameterized Gate instance into a QuantumCircuit now creates a copy of that gate which is used in the circuit. If changes are made to the instance inserted into the circuit it will no longer be reflected in the gate in the circuit. This change was made to fix an issue when inserting a single parameterized Gate object into multiple circuits.
The function qiskit.result.marginal_counts() now, by default, does not modify the qiskit.result.Result instance parameter. Previously, the Result object was always modified in place. A new kwarg inplace has been added marginal_counts() which enables using the previous behavior when inplace=True is set.
The U3Gate definition has been changed to be in terms of the UGate class. The UGate class has no definition. It is therefore not possible to unroll every circuit in terms of U3 and CX anymore. Instead, U and CX can be used for every circuit.
The deprecated support for running Qiskit Terra with Python 3.5 has been removed. To use Qiskit Terra from this release onward you will now need to use at least Python 3.6. If you are using Python 3.5 the last version which will work is Qiskit Terra 0.15.2.
In the PulseBackendConfiguration in the hamiltonian attributes the vars field is now returned in a unit of Hz instead of the previously used GHz. This change was made to be consistent with the units used with the other attributes in the class.
The previously deprecated support for passing in a dictionary as the first positional argument to DAGNode constructor has been removed. Using a dictonary for the first positional argument was deprecated in the 0.13.0 release. To create a DAGNode object now you should directly pass the attributes as kwargs on the constructor.
The keyword arguments for the circuit gate methods (for example: qiskit.circuit.QuantumCircuit.cx) q, ctl*, and tgt*, which were deprecated in the 0.12.0 release, have been removed. Instead, only qubit, control_qubit* and target_qubit* can be used as named arguments for these methods.
The previously deprecated module qiskit.extensions.standard has been removed. This module has been deprecated since the 0.14.0 release. The qiskit.circuit.library can be used instead. Additionally, all the gate classes previously in qiskit.extensions.standard are still importable from qiskit.extensions.
The previously deprecated gates in the module qiskit.extensions.quantum_initializer: DiagGate, UCG`, UCPauliRotGate, UCRot, UCRXGate, UCX, UCRYGate, UCY, UCRZGate, UCZ have been removed. These were all deprecated in the 0.14.0 release and have alternatives available in the circuit library (qiskit.circuit.library).
The previously deprecated qiskit.circuit.QuantumCircuit gate method iden() has been removed. This was deprecated in the 0.13.0 release and i() or id() can be used instead.

Deprecation Notes¶

The use of a numpy.ndarray for a parameter in the params kwarg for the constructor of the Gate class and subclasses has been deprecated and will be removed in future releases. This was done as part of the refactoring of how parms type checking is handled for the Gate class. If you have a custom gate class which is a subclass of Gate directly (or via a different parent in the hierarchy) that accepts an ndarray parameter, you should define a custom validate_parameter() method for your class that will return the allowed parameter type. For example:
```
def validate_parameter(self, parameter):
    """Custom gate parameter has to be an ndarray."""
    if isinstance(parameter, numpy.ndarray):
        return parameter
    else:
        raise CircuitError("invalid param type {0} in gate "
                           "{1}".format(type(parameter), self.name))
```
The num_ancilla_qubits property of the PiecewiseLinearPauliRotations and PolynomialPauliRotations classes has been deprecated and will be removed in a future release. Instead the property num_ancillas should be used instead. This was done to make it consistent with the QuantumCircuit method num_ancillas().
The qiskit.circuit.library.MSGate class has been deprecated, but will remain in place to allow loading of old jobs. It has been replaced with the qiskit.circuit.library.GMS class which should be used instead.
The MSBasisDecomposer transpiler pass has been deprecated and will be removed in a future release. The qiskit.transpiler.passes.BasisTranslator pass can be used instead.

The QuantumCircuit methods u1, u2 and u3 are now deprecated. Instead the following replacements can be used.

u1(theta) = p(theta) = u(0, 0, theta)
u2(phi, lam) = u(pi/2, phi, lam) = p(pi/2 + phi) sx p(pi/2 lam)
u3(theta, phi, lam) = u(theta, phi, lam) = p(phi + pi) sx p(theta + pi) sx p(lam)

The gate classes themselves, U1Gate, U2Gate and U3Gate remain, to allow loading of old jobs.

Bug Fixes¶

The Result class’s methods data(), get_memory(), get_counts(), get_unitary(), and get_statevector ` will now emit a warning when the ``experiment`() kwarg is specified for attempting to fetch results using either a QuantumCircuit or Schedule instance, when more than one entry matching the instance name is present in the Result object. Note that only the first entry matching this name will be returned. Fixes #3207
The qiskit.circuit.QuantumCircuit method append() can now be used to insert one parameterized gate instance into multiple circuits. This fixes a previous issue where inserting a single parameterized Gate object into multiple circuits would cause failures when one circuit had a parameter assigned. Fixes #4697
Previously the qiskit.execute.execute() function would incorrectly disallow both the backend and pass_manager kwargs to be specified at the same time. This has been fixed so that both backend and pass_manager can be used together on calls to execute(). Fixes #5037
The QuantumCircuit method unitary() method has been fixed to accept a single integer for the qarg argument (when adding a 1-qubit unitary). The allowed types for the qargs argument are now int, Qubit, or a list of integers. Fixes #4944
Previously, calling inverse() on a BlueprintCircuit object could fail if its internal data property was not yet populated. This has been fixed so that the calling inverse() will populate the internal data before generating the inverse of the circuit. Fixes #5140
Fixed an issue when creating a qiskit.result.Counts object from an empty data dictionary. Now this will create an empty Counts object. The most_frequent() method is also updated to raise a more descriptive exception when the object is empty. Fixes #5017
Fixes a bug where setting ctrl_state of a UnitaryGate would be applied twice; once in the creation of the matrix for the controlled unitary and again when calling the definition() method of the qiskit.circuit.ControlledGate class. This would give the appearence that setting ctrl_state had no effect.
Previously the ControlledGate method inverse() would not preserve the ctrl_state parameter in some cases. This has been fixed so that calling inverse() will preserve the value ctrl_state in its output.
Fixed a bug in the mpl output backend of the circuit drawer qiskit.circuit.QuantumCircuit.draw() and qiskit.visualization.circuit_drawer() that would cause the drawer to fail if the style kwarg was set to a string. The correct behavior would be to treat that string as a path to a JSON file containing the style sheet for the visualization. This has been fixed, and warnings are raised if the JSON file for the style sheet can’t be loaded.
Fixed an error where loading a QASM file via from_qasm_file() or from_qasm_str() would fail if a u, phase(p), sx, or sxdg gate were present in the QASM file. Fixes #5156
Fixed a bug that would potentially cause registers to be mismapped when unrolling/decomposing a gate defined with only one 2-qubit operation.

Aer 0.7.0¶

Prelude¶

This 0.7.0 release includes numerous performance improvements and significant enhancements to the simulator interface, and drops support for Python 3.5. The main interface changes are configurable simulator backends, and constructing preconfigured simulators from IBMQ backends. Noise model an basis gate support has also been extended for most of the Qiskit circuit library standard gates, including new support for 1 and 2-qubit rotation gates. Performance improvements include adding SIMD support to the density matrix and unitary simulation methods, reducing the used memory and improving the performance of circuits using statevector and density matrix snapshots, and adding support for Kraus instructions to the gate fusion circuit optimization for greatly improving the performance of noisy statevector simulations.

New Features¶

Adds basis gate support for the qiskit.circuit.Delay instruction to the StatevectorSimulator, UnitarySimulator, and QasmSimulator. Note that this gate is treated as an identity gate during simulation and the delay length parameter is ignored.
Adds basis gate support for the single-qubit gate qiskit.circuit.library.UGate to the StatevectorSimulator, UnitarySimulator, and the "statevector", "density_matrix", "matrix_product_state", and "extended_stabilizer" methods of the QasmSimulator.
Adds basis gate support for the phase gate qiskit.circuit.library.PhaseGate to the StatevectorSimulator, StatevectorSimulator, UnitarySimulator, and the "statevector", "density_matrix", "matrix_product_state", and "extended_stabilizer" methods of the QasmSimulator.
Adds basis gate support for the controlled-phase gate qiskit.circuit.library.CPhaseGate to the StatevectorSimulator, StatevectorSimulator, UnitarySimulator, and the "statevector", "density_matrix", and "matrix_product_state" methods of the QasmSimulator.
Adds support for the multi-controlled phase gate qiskit.circuit.library.MCPhaseGate to the StatevectorSimulator, UnitarySimulator, and the "statevector" method of the QasmSimulator.
Adds support for the \(\sqrt(X)\) gate qiskit.circuit.library.SXGate to the StatevectorSimulator, UnitarySimulator, and QasmSimulator.
Adds support for 1 and 2-qubit Qiskit circuit library rotation gates RXGate, RYGate, RZGate, RGate, RXXGate, RYYGate, RZZGate, RZXGate to the StatevectorSimulator, UnitarySimulator, and the "statevector" and "density_matrix" methods of the QasmSimulator.
Adds support for multi-controlled rotation gates "mcr", "mcrx", "mcry", "mcrz" to the StatevectorSimulator, UnitarySimulator, and the "statevector" method of the QasmSimulator.
Make simulator backends configurable. This allows setting persistant options such as simulation method and noise model for each simulator backend object.

The QasmSimulator and PulseSimulator can also be configured from an IBMQBackend backend object using the :meth:`~qiskit.providers.aer.QasmSimulator.from_backend method. For the QasmSimulator this will configure the coupling map, basis gates, and basic device noise model based on the backend configuration and properties. For the PulseSimulator the system model and defaults will be configured automatically from the backend configuration, properties and defaults.

For example a noisy density matrix simulator backend can be constructed as QasmSimulator(method='density_matrix', noise_model=noise_model), or an ideal matrix product state simulator as QasmSimulator(method='matrix_product_state').

A benefit is that a PulseSimulator instance configured from a backend better serves as a drop-in replacement to the original backend, making it easier to swap in and out a simulator and real backend, e.g. when testing code on a simulator before using a real backend. For example, in the following code-block, the PulseSimulator is instantiated from the FakeArmonk() backend. All configuration and default data is copied into the simulator instance, and so when it is passed as an argument to assemble, it behaves as if the original backend was supplied (e.g. defaults from FakeArmonk will be present and used by assemble).
```
armonk_sim = qiskit.providers.aer.PulseSimulator.from_backend(FakeArmonk())
pulse_qobj = assemble(schedules, backend=armonk_sim)
armonk_sim.run(pulse_qobj)
```
While the above example is small, the demonstrated “drop-in replacement” behavior should greatly improve the usability in more complicated work-flows, e.g. when calibration experiments are constructed using backend attributes.
Adds support for qobj global phase to the StatevectorSimulator, UnitarySimulator, and statevector methods of the QasmSimulator.
Improves general noisy statevector simulation performance by adding a Kraus method to the gate fusion circuit optimization that allows applying gate fusion to noisy statevector simulations with general Kraus noise.
Use move semantics for statevector and density matrix snapshots for the « statevector » and « density_matrix » methods of the QasmSimulator if they are the final instruction in a circuit. This reduces the memory usage of the simulator improves the performance by avoiding copying a large array in the results.
Adds support for general Kraus QauntumError gate errors in the NoiseModel to the "matrix_product_state" method of the QasmSimulator.
Adds support for density matrix snapshot instruction qiskit.providers.aer.extensions.SnapshotDensityMatrix to the "matrix_product_state" method of the QasmSimulator.
Extends the SIMD vectorization of the statevector simulation method to the unitary matrix, superoperator matrix, and density matrix simulation methods. This gives roughtly a 2x performance increase general simulation using the UnitarySimulator, the "density_matrix" method of the QasmSimulator, gate fusion, and noise simulation.
Adds a custom vector class to C++ code that has better integration with Pybind11. This haves the memory requirement of the StatevectorSimulator by avoiding an memory copy during Python binding of the final simulator state.

Upgrade Notes¶

AER now uses Lapack to perform some matrix related computations. It uses the Lapack library bundled with OpenBlas (already available in Linux and Macos typical OpenBlas dsitributions; Windows version distributed with AER) or with the accelerate framework in MacOS.
The deprecated support for running qiskit-aer with Python 3.5 has been removed. To use qiskit-aer >=0.7.0 you will now need at least Python 3.6. If you are using Python 3.5 the last version which will work is qiskit-aer 0.6.x.
Updates gate fusion default thresholds so that gate fusion will be applied to circuits with of more than 14 qubits for statevector simulations on the StatevectorSimulator and QasmSimulator.

For the "density_matrix" method of the QasmSimulator and for the UnitarySimulator gate fusion will be applied to circuits with more than 7 qubits.

Custom qubit threshold values can be set using the fusion_threshold backend option ie backend.set_options(fusion_threshold=10)
Changes fusion_threshold backend option to apply fusion when the number of qubits is above the threshold, not equal or above the threshold, to match the behavior of the OpenMP qubit threshold parameter.

Deprecation Notes¶

qiskit.providers.aer.noise.NoiseModel.set_x90_single_qubit_gates() has been deprecated as unrolling to custom basis gates has been added to the qiskit transpiler. The correct way to use an X90 based noise model is to define noise on the Sqrt(X) "sx" or "rx" gate and one of the single-qubit phase gates "u1", "rx", or "p" in the noise model.
The variance kwarg of Snapshot instructions has been deprecated. This function computed the sample variance in the snapshot due to noise model sampling, not the variance due to measurement statistics so was often being used incorrectly. If noise modeling variance is required single shot snapshots should be used so variance can be computed manually in post-processing.

Bug Fixes¶

Fixes bug in the StatevectorSimulator that caused it to always run as CPU with double-precision without SIMD/AVX2 support even on systems with AVX2, or when single-precision or the GPU method was specified in the backend options.
Fixes some for-loops in C++ code that were iterating over copies rather than references of container elements.
Fixes a bug where snapshot data was always copied from C++ to Python rather than moved where possible. This will halve memory usage and improve simulation time when using large statevector or density matrix snapshots.
Fix State::snapshot_pauli_expval to return correct Y expectation value in stabilizer simulator. Refer to #895 <https://github.com/Qiskit/qiskit-aer/issues/895> for more details.
The controller_execute wrappers have been adjusted to be functors (objects) rather than free functions. Among other things, this allows them to be used in multiprocessing.pool.map calls.
Add missing available memory checks for the StatevectorSimulator and UnitarySimulator. This throws an exception if the memory required to simulate the number of qubits in a circuit exceeds the available memory of the system.

Ignis 0.5.0¶

Prelude¶

This release includes a new module for expectation value measurement error mitigation, improved plotting functionality for quantum volume experiments, several bug fixes, and drops support for Python 3.5.

New Features¶

The qiskit.ignis.verification.randomized_benchmarking.randomized_benchmarking_seq() function allows an optional input of gate objects as interleaved_elem. In addition, the CNOT-Dihedral class qiskit.ignis.verification.randomized_benchmarking.CNOTDihedral has a new method to_instruction, and the existing from_circuit method has an optional input of an Instruction (in addition to QuantumCircuit).
The qiskit.ignis.verification.randomized_benchmarking.CNOTDihedral now contains the following new features. Initialization from various types of objects: CNOTDihedral, ScalarOp, QuantumCircuit, Instruction and Pauli. Converting to a matrix using to_matrix and to an operator using to_operator. Tensor product methods tensor and expand. Calculation of the adjoint, conjugate and transpose using conjugate, adjoint and transpose methods. Verify that an element is CNOTDihedral using is_cnotdihedral method. Decomposition method to_circuit of a CNOTDihedral element into a circuit was extended to allow any number of qubits, based on the function decompose_cnotdihedral_general.

Adds expectation value measurement error mitigation to the mitigation module. This supports using complete N-qubit assignment matrix, single-qubit tensored assignment matrix, or continuous time Markov process (CTMP) [1] measurement error mitigation when computing expectation values of diagonal operators from counts dictionaries. Expectation values are computed using the using the qiskit.ignis.mitigation.expectation_value() function.

Calibration circuits for calibrating a measurement error mitigator are generated using the qiskit.ignis.mitigation.expval_meas_mitigator_circuits() function, and the result fitted using the qiskit.ignis.mitigation.ExpvalMeasMitigatorFitter class. The fitter returns a mitigator object can the be supplied as an argument to the expectation_value() function to apply mitigation.

[1] S Bravyi, S Sheldon, A Kandala, DC Mckay, JM Gambetta,: Mitigating measurement errors in multi-qubit experiments, arXiv:2006.14044 [quant-ph].

Example:

The following example shows calibrating a 5-qubit expectation value measurement error mitigator using the 'tensored' method.

from qiskit import execute
from qiskit.test.mock import FakeVigo
import qiskit.ignis.mitigation as mit

backend = FakeVigo()
num_qubits = backend.configuration().num_qubits

# Generate calibration circuits
circuits, metadata = mit.expval_meas_mitigator_circuits(
    num_qubits, method='tensored')
result = execute(circuits, backend, shots=8192).result()

# Fit mitigator
mitigator = mit.ExpvalMeasMitigatorFitter(result, metadata).fit()

# Plot fitted N-qubit assignment matrix
mitigator.plot_assignment_matrix()

<matplotlib.axes._subplots.AxesSubplot at 0x7f5665dfd0a0>

The following shows how to use the above mitigator to apply measurement error mitigation to expectation value computations

from qiskit import QuantumCircuit

# Test Circuit with expectation value -1.
qc = QuantumCircuit(num_qubits)
qc.x(range(num_qubits))
qc.measure_all()

# Execute
shots = 8192
seed_simulator = 1999
result = execute(qc, backend, shots=8192, seed_simulator=1999).result()
counts = result.get_counts(0)

# Expectation value of Z^N without mitigation
expval_nomit, error_nomit = mit.expectation_value(counts)
print('Expval (no mitigation): {:.2f} \u00B1 {:.2f}'.format(
    expval_nomit, error_nomit))

# Expectation value of Z^N with mitigation
expval_mit, error_mit = mit.expectation_value(counts,
    meas_mitigator=mitigator)
print('Expval (with mitigation): {:.2f} \u00B1 {:.2f}'.format(
    expval_mit, error_mit))

Expval (no mitigation): -0.66 ± 0.01
Expval (with mitigation): -1.01 ± 0.01

Adds Numba as an optional dependency. Numba is used to significantly increase the performance of the qiskit.ignis.mitigation.CTMPExpvalMeasMitigator class used for expectation value measurement error mitigation with the CTMP method.
Add two methods to qiskit.ignis.verification.quantum_volume.QVFitter.
- qiskit.ignis.verification.quantum_volume.QVFitter.calc_z_value() to calculate z value in standard normal distribution using mean and standard deviation sigma. If sigma = 0, it raises a warning and assigns a small value (1e-10) for sigma so that the code still runs.
- qiskit.ignis.verification.quantum_volume.QVFitter.calc_confidence_level() to calculate confidence level using z value.
Store confidence level even when hmean < 2/3 in qiskit.ignis.verification.quantum_volume.QVFitter.qv_success().
Add explanations for how to calculate statistics based on binomial distribution in qiskit.ignis.verification.quantum_volume.QVFitter.calc_statistics().
The qiskit.ignis.verification.QVFitter method plot_qv_data() has been updated to return a matplotlib.Figure object. Previously, it would not return anything. By returning a figure this makes it easier to integrate the visualizations into a larger matplotlib workflow.
The error bars in the figure produced by the qiskit.ignis.verification.QVFitter method qiskit.ignis.verification.QVFitter.plot_qv_data() has been updated to represent two-sigma confidence intervals. Previously, the error bars represent one-sigma confidence intervals. The success criteria of Quantum Volume benchmarking requires heavy output probability > 2/3 with one-sided two-sigma confidence (~97.7%). Changing error bars to represent two-sigma confidence intervals allows easily identification of success in the figure.
A new kwarg, figsize has been added to the qiskit.ignis.verification.QVFitter method qiskit.ignis.verification.QVFitter.plot_qv_data(). This kwarg takes in a tuple of the form (x, y) where x and y are the dimension in inches to make the generated plot.
The qiskit.ignis.verification.quantum_volume.QVFitter.plot_hop_accumulative() method has been added to plot heavy output probability (HOP) vs number of trials similar to Figure 2a of Quantum Volume 64 paper (arXiv:2008.08571). HOP of individual trials are plotted as scatters and cummulative HOP are plotted in red line. Two-sigma confidence intervals are plotted as shaded area and 2/3 success threshold is plotted as dashed line.
The qiskit.ignis.verification.quantum_volume.QVFitter.plot_qv_trial() method has been added to plot individual trials, leveraging on the qiskit.visualization.plot_histogram() method from Qiskit Terra. Bitstring counts are plotted as overlapping histograms for ideal (hollow) and experimental (filled) values. Experimental heavy output probability are shown on the legend. Median probability is plotted as red dashed line.

Upgrade Notes¶

The deprecated support for running qiskit-ignis with Python 3.5 has been removed. To use qiskit-ignis >=0.5.0 you will now need at least Python 3.6. If you are using Python 3.5 the last version which will work is qiskit-ignis 0.4.x.

Bug Fixes¶

Fixing a bug in the class qiskit.ignis.verification.randomized_benchmarking.CNOTDihedral for elements with more than 5 quits.
Fix the confidence level threshold for qiskit.ignis.verification.quantum_volume.QVFitter.qv_success() to 0.977 corresponding to z = 2 as defined by the QV paper Algorithm 1.
Fix a bug at qiskit.ignis.verification.randomized_benchmarking.randomized_benchmarking_seq() which caused all the subsystems with the same size in the given rb_pattern to have the same gates when a “rand_seed” parameter was given to the function.

Aqua 0.8.0¶

Prelude¶

This release introduces an interface for running the available methods for Bosonic problems. In particular we introduced a full interface for running vibronic structure calculations.

This release introduces an interface for excited states calculations. It is now easier for the user to create a general excited states calculation. This calculation is based on a Driver which provides the relevant information about the molecule, a Transformation which provides the information about the mapping of the problem into a qubit Hamiltonian, and finally a Solver. The Solver is the specific way which the excited states calculation is done (the algorithm). This structure follows the one of the ground state calculations. The results are modified to take lists of expectation values instead of a single one. The QEOM and NumpyEigensolver are adapted to the new structure. A factory is introduced to run a numpy eigensolver with a specific filter (to target states of specific symmetries).

VQE expectation computation with Aer qasm_simulator now defaults to a computation that has the expected shot noise behavior.

New Features¶

Introduced an option warm_start that should be used when tuning other options does not help. When this option is enabled, a relaxed problem (all variables are continuous) is solved first and the solution is used to initialize the state of the optimizer before it starts the iterative process in the solve method.

The amplitude estimation algorithms now use QuantumCircuit objects as inputs to specify the A- and Q operators. This change goes along with the introduction of the GroverOperator in the circuit library, which allows an intuitive and fast construction of different Q operators. For example, a Bernoulli-experiment can now be constructed as

import numpy as np
from qiskit import QuantumCircuit
from qiskit.aqua.algorithms import AmplitudeEstimation

probability = 0.5
angle = 2 * np.sqrt(np.arcsin(probability))
a_operator = QuantumCircuit(1)
a_operator.ry(angle, 0)

# construct directly
q_operator = QuantumCircuit(1)
q_operator.ry(2 * angle, 0)

# construct via Grover operator
from qiskit.circuit.library import GroverOperator
oracle = QuantumCircuit(1)
oracle.z(0)  # good state = the qubit is in state |1>
q_operator = GroverOperator(oracle, state_preparation=a_operator)

# use default construction in QAE
q_operator = None

ae = AmplitudeEstimation(a_operator, q_operator)

Add the possibility to compute Conditional Value at Risk (CVaR) expectation values.

Given a diagonal observable H, often corresponding to the objective function of an optimization problem, we are often not as interested in minimizing the average energy of our observed measurements. In this context, we are satisfied if at least some of our measurements achieve low energy. (Note that this is emphatically not the case for chemistry problems).

To this end, one might consider using the best observed sample as a cost function during variational optimization. The issue here, is that this can result in a non-smooth optimization surface. To resolve this issue, we can smooth the optimization surface by using not just the best observed sample, but instead average over some fraction of best observed samples. This is exactly what the CVaR estimator accomplishes [1].

Let \(\alpha\) be a real number in \([0,1]\) which specifies the fraction of best observed samples which are used to compute the objective function. Observe that if \(\alpha = 1\), CVaR is equivalent to a standard expectation value. Similarly, if \(\alpha = 0\), then CVaR corresponds to using the best observed sample. Intermediate values of \(\alpha\) interpolate between these two objective functions.

The functionality to use CVaR is included into the operator flow through a new subclass of OperatorStateFn called CVaRMeasurement. This new StateFn object is instantied in the same way as an OperatorMeasurement with the exception that it also accepts an alpha parameter and that it automatically enforces the is_measurement attribute to be True. Observe that it is unclear what a CVaRStateFn would represent were it not a measurement.

Examples:
```
qc = QuantumCircuit(1)
qc.h(0)
op = CVaRMeasurement(Z, alpha=0.5) @ CircuitStateFn(primitive=qc, coeff=1.0)
result = op.eval()
```
Similarly, an operator corresponding to a standard expectation value can be converted into a CVaR expectation using the CVaRExpectation converter.

Examples:
```
qc = QuantumCircuit(1)
qc.h(0)
op = ~StateFn(Z) @ CircuitStateFn(primitive=qc, coeff=1.0)
cvar_expecation = CVaRExpectation(alpha=0.1).convert(op)
result = cvar_expecation.eval()
```
See [1] for additional details regarding this technique and it’s empircal performance.

References:

[1]: Barkoutsos, P. K., Nannicini, G., Robert, A., Tavernelli, I., and Woerner, S.,
« Improving Variational Quantum Optimization using CVaR » arXiv:1907.04769
New interface Eigensolver for Eigensolver algorithms.
An interface for excited states calculation has been added to the chemistry module. It is now easier for the user to create a general excited states calculation. This calculation is based on a Driver which provides the relevant information about the molecule, a Transformation which provides the information about the mapping of the problem into a qubit Hamiltonian, and finally a Solver. The Solver is the specific way which the excited states calculation is done (the algorithm). This structure follows the one of the ground state calculations. The results are modified to take lists of expectation values instead of a single one. The QEOM and NumpyEigensolver are adapted to the new structure. A factory is introduced to run a numpy eigensolver with a specific filter (to target states of specific symmetries).
In addition to the workflows for solving Fermionic problems, interfaces for calculating Bosonic ground and excited states have been added. In particular we introduced a full interface for running vibronic structure calculations.
The OrbitalOptimizationVQE has been added as new ground state solver in the chemistry module. This solver allows for the simulatneous optimization of the variational parameters and the orbitals of the molecule. The algorithm is introduced in Sokolov et al., The Journal of Chemical Physics 152 (12).
A new algorithm has been added: the Born Openheimer Potential Energy surface for the calculation of potential energy surface along different degrees of freedom of the molecule. The algorithm is called BOPESSampler. It further provides functionalities of fitting the potential energy surface to an analytic function of predefined potentials.
A feasibility check of the obtained solution has been added to all optimizers in the optimization stack. This has been implemented by adding two new methods to QuadraticProgram: * get_feasibility_info(self, x: Union[List[float], np.ndarray]) accepts an array and returns whether this solution is feasible and a list of violated variables(violated bounds) and a list of violated constraints. * is_feasible(self, x: Union[List[float], np.ndarray]) accepts an array and returns whether this solution is feasible or not.
Add circuit-based versions of FixedIncomeExpectedValue, EuropeanCallDelta, GaussianConditionalIndependenceModel and EuropeanCallExpectedValue to qiskit.finance.applications.
Gradient Framework. qiskit.operators.gradients Given an operator that represents either a quantum state resp. an expectation value, the gradient framework enables the evaluation of gradients, natural gradients, Hessians, as well as the Quantum Fisher Information.

Suppose a parameterized quantum state |ψ(θ)〉 = V(θ)|ψ〉 with input state |ψ〉 and parametrized Ansatz V(θ), and an Operator O(ω).

Gradients: We want to compute \(d⟨ψ(θ)|O(ω)|ψ(θ)〉/ dω\) resp. \(d⟨ψ(θ)|O(ω)|ψ(θ)〉/ dθ\) resp. \(d⟨ψ(θ)|i〉⟨i|ψ(θ)〉/ dθ\).

The last case corresponds to the gradient w.r.t. the sampling probabilities of |ψ(θ). These gradients can be computed with different methods, i.e. a parameter shift, a linear combination of unitaries and a finite difference method.

Examples:
```
x = Parameter('x')
ham = x * X
a = Parameter('a')

q = QuantumRegister(1)
qc = QuantumCircuit(q)
qc.h(q)
qc.p(params[0], q[0])
op = ~StateFn(ham) @ CircuitStateFn(primitive=qc, coeff=1.)

value_dict = {x: 0.1, a: np.pi / 4}

ham_grad = Gradient(grad_method='param_shift').convert(operator=op, params=[x])
ham_grad.assign_parameters(value_dict).eval()

state_grad = Gradient(grad_method='lin_comb').convert(operator=op, params=[a])
state_grad.assign_parameters(value_dict).eval()

prob_grad = Gradient(grad_method='fin_diff').convert(operator=CircuitStateFn(primitive=qc, coeff=1.),
                                                     params=[a])
prob_grad.assign_parameters(value_dict).eval()
```
Hessians: We want to compute \(d^2⟨ψ(θ)|O(ω)|ψ(θ)〉/ dω^2\) resp. \(d^2⟨ψ(θ)|O(ω)|ψ(θ)〉/ dθ^2\) resp. \(d^2⟨ψ(θ)|O(ω)|ψ(θ)〉/ dθdω\) resp. \(d^2⟨ψ(θ)|i〉⟨i|ψ(θ)〉/ dθ^2\).

The last case corresponds to the Hessian w.r.t. the sampling probabilities of |ψ(θ). Just as the first order gradients, the Hessians can be evaluated with different methods, i.e. a parameter shift, a linear combination of unitaries and a finite difference method. Given a tuple of parameters Hessian().convert(op, param_tuple) returns the value for the second order derivative. If a list of parameters is given Hessian().convert(op, param_list) returns the full Hessian for all the given parameters according to the given parameter order.

QFI: The Quantum Fisher Information QFI is a metric tensor which is representative for the representation capacity of a parameterized quantum state |ψ(θ)〉 = V(θ)|ψ〉 generated by an input state |ψ〉 and a parametrized Ansatz V(θ). The entries of the QFI for a pure state read \([QFI]kl= Re[〈∂kψ|∂lψ〉−〈∂kψ|ψ〉〈ψ|∂lψ〉] * 4\).

Just as for the previous derivative types, the QFI can be computed using different methods: a full representation based on a linear combination of unitaries implementation, a block-diagonal and a diagonal representation based on an overlap method.

Examples:
```
q = QuantumRegister(1)
qc = QuantumCircuit(q)
qc.h(q)
qc.p(params[0], q[0])
op = ~StateFn(ham) @ CircuitStateFn(primitive=qc, coeff=1.)

value_dict = {x: 0.1, a: np.pi / 4}
qfi = QFI('lin_comb_full').convert(operator=CircuitStateFn(primitive=qc, coeff=1.), params=[a])
qfi.assign_parameters(value_dict).eval()
```
The combination of the QFI and the gradient lead to a special form of a gradient, namely

NaturalGradients: The natural gradient is a special gradient method which rescales a gradient w.r.t. a state parameter with the inverse of the corresponding Quantum Fisher Information (QFI) \(QFI^-1 d⟨ψ(θ)|O(ω)|ψ(θ)〉/ dθ\). Hereby, we can choose a gradient as well as a QFI method and a regularization method which is used together with a least square solver instead of exact invertion of the QFI:

Examples:
```
op = ~StateFn(ham) @ CircuitStateFn(primitive=qc, coeff=1.)
nat_grad = NaturalGradient(grad_method='lin_comb, qfi_method='lin_comb_full', \
                           regularization='ridge').convert(operator=op, params=params)
```
The gradient framework is also compatible with the optimizers from qiskit.aqua.components.optimizers. The derivative classes come with a gradient_wrapper() function which returns the corresponding callable.
Introduces transformations for the fermionic and bosonic transformation of a problem instance. Transforms the fermionic operator to qubit operator. Respective class for the transformation is fermionic_transformation Introduces in algorithms ground_state_solvers for the calculation of ground state properties. The calculation can be done either using an MinimumEigensolver or using AdaptVQE Introduces chemistry/results where the eigenstate_result and the electronic_structure_result are also used for the algorithms. Introduces Minimum Eigensolver factories minimum_eigensolver_factories where chemistry specific minimum eigensolvers can be initialized Introduces orbital optimization vqe oovqe as a ground state solver for chemistry applications
New Algorithm result classes:

Grover method _run() returns class GroverResult. AmplitudeEstimation method _run() returns class AmplitudeEstimationResult. IterativeAmplitudeEstimation method _run() returns class IterativeAmplitudeEstimationResult. MaximumLikelihoodAmplitudeEstimation method _run() returns class MaximumLikelihoodAmplitudeEstimationResult.

All new result classes are backwards compatible with previous result dictionary.
New Linear Solver result classes:

HHL method _run() returns class HHLResult. NumPyLSsolver method _run() returns class NumPyLSsolverResult.

All new result classes are backwards compatible with previous result dictionary.
MinimumEigenOptimizationResult now exposes properties: samples and eigensolver_result. The latter is obtained from the underlying algorithm used by the optimizer and specific to the algorithm. RecursiveMinimumEigenOptimizer now returns an instance of the result class RecursiveMinimumEigenOptimizationResult which in turn may contains intermediate results obtained from the underlying algorithms. The dedicated result class exposes properties replacements and history that are specific to this optimizer. The depth of the history is managed by the history parameter of the optimizer.
GroverOptimizer now returns an instance of GroverOptimizationResult and this result class exposes properties operation_counts, n_input_qubits, and n_output_qubits directly. These properties are not available in the raw_results dictionary anymore.
SlsqpOptimizer now returns an instance of SlsqpOptimizationResult and this result class exposes additional properties specific to the SLSQP implementation.
Support passing QuantumCircuit objects as generator circuits into the QuantumGenerator.
Removes the restriction to real input vectors in CircuitStateFn.from_vector. The method calls extensions.Initialize. The latter explicitly supports (in API and documentation) complex input vectors. So this restriction seems unnecessary.
Simplified AbelianGrouper using a graph coloring algorithm of retworkx. It is faster than the numpy-based coloring algorithm.
Allow calling eval on state function objects with no argument, which returns the VectorStateFn representation of the state function. This is consistent behavior with OperatorBase.eval, which returns the MatrixOp representation, if no argument is passed.
Adds max_iterations to the VQEAdapt class in order to allow limiting the maximum number of iterations performed by the algorithm.
VQE expectation computation with Aer qasm_simulator now defaults to a computation that has the expected shot noise behavior. The special Aer snapshot based computation, that is much faster, with the ideal output similar to state vector simulator, may still be chosen but like before Aqua 0.7 it now no longer defaults to this but can be chosen.

Upgrade Notes¶

Extension of the previous Analytic Quantum Gradient Descent (AQGD) classical optimizer with the AQGD with Epochs. Now AQGD performs the gradient descent optimization with a momentum term, analytic gradients, and an added customized step length schedule for parametrized quantum gates. Gradients are computed « analytically » using the quantum circuit when evaluating the objective function.
The deprecated support for running qiskit-aqua with Python 3.5 has been removed. To use qiskit-aqua >=0.8.0 you will now need at least Python 3.6. If you are using Python 3.5 the last version which will work is qiskit-aqua 0.7.x.
Added retworkx as a new dependency.

Deprecation Notes¶

The i_objective argument of the amplitude estimation algorithms has been renamed to objective_qubits.
TransformationType
QubitMappingType

Deprecate the CircuitFactory and derived types. The CircuitFactory has been introduced as temporary class when the QuantumCircuit missed some features necessary for applications in Aqua. Now that the circuit has all required functionality, the circuit factory can be removed. The replacements are shown in the following table.

Circuit factory class               | Replacement
------------------------------------+-----------------------------------------------
CircuitFactory                      | use QuantumCircuit
                                    |
UncertaintyModel                    | -
UnivariateDistribution              | -
MultivariateDistribution            | -
NormalDistribution                  | qiskit.circuit.library.NormalDistribution
MultivariateNormalDistribution      | qiskit.circuit.library.NormalDistribution
LogNormalDistribution               | qiskit.circuit.library.LogNormalDistribution
MultivariateLogNormalDistribution   | qiskit.circuit.library.LogNormalDistribution
UniformDistribution                 | qiskit.circuit.library.UniformDistribution
MultivariateUniformDistribution     | qiskit.circuit.library.UniformDistribution
UnivariateVariationalDistribution   | use parameterized QuantumCircuit
MultivariateVariationalDistribution | use parameterized QuantumCircuit
                                    |
UncertaintyProblem                  | -
UnivariateProblem                   | -
MultivariateProblem                 | -
UnivariatePiecewiseLinearObjective  | qiskit.circuit.library.LinearAmplitudeFunction

The ising convert classes qiskit.optimization.converters.QuadraticProgramToIsing and qiskit.optimization.converters.IsingToQuadraticProgram have been deprecated and will be removed in a future release. Instead the qiskit.optimization.QuadraticProgram methods to_ising() and from_ising() should be used instead.
Deprecate the WeightedSumOperator which has been ported to the circuit library as WeightedAdder in qiskit.circuit.library.
Core Hamiltonian class is deprecated in favor of the FermionicTransformation Chemistry Operator class is deprecated in favor of the tranformations minimum_eigen_solvers/vqe_adapt is also deprecated and moved as an implementation of the ground_state_solver interface applications/molecular_ground_state_energy is deprecated in favor of ground_state_solver
Optimizer.SupportLevel nested enum is replaced by OptimizerSupportLevel and Optimizer.SupportLevel was removed. Use, for example, OptimizerSupportLevel.required instead of Optimizer.SupportLevel.required.
Deprecate the UnivariateVariationalDistribution and MultivariateVariationalDistribution as input to the QuantumGenerator. Instead, plain QuantumCircuit objects can be used.
Ignored fast and use_nx options of AbelianGrouper.group_subops to be removed in the future release.
GSLS optimizer class deprecated __init__ parameter max_iter in favor of maxiter. SPSA optimizer class deprecated __init__ parameter max_trials in favor of maxiter. optimize_svm function deprecated max_iters parameter in favor of maxiter. ADMMParameters class deprecated __init__ parameter max_iter in favor of maxiter.

Bug Fixes¶

The UCCSD excitation list, comprising single and double excitations, was not being generated correctly when an active space was explicitly provided to UCSSD via the active_(un)occupied parameters.
For the amplitude estimation algorithms, we define the number of oracle queries as number of times the Q operator/Grover operator is applied. This includes the number of shots. That factor has been included in MLAE and IQAE but was missing in the “standard” QAE.
Fix CircuitSampler.convert, so that the is_measurement property is propagated to converted StateFns.
Fix double calculation of coefficients in :meth`~qiskit.aqua.operators.VectorStateFn.to_circuit_op`.
Calling PauliTrotterEvolution.convert on an operator including a term that is a scalar multiple of the identity gave an incorrect circuit, one that ignored the scalar coefficient. This fix includes the effect of the coefficient in the global_phase property of the circuit.
Make ListOp.num_qubits check that all ops in list have the same num_qubits Previously, the number of qubits in the first operator in the ListOp was returned. With this change, an additional check is made that all other operators also have the same number of qubits.
Make PauliOp.exp_i() generate the correct matrix with the following changes. 1) There was previously an error in the phase of a factor of 2. 2) The global phase was ignored when converting the circuit to a matrix. We now use qiskit.quantum_info.Operator, which is generally useful for converting a circuit to a unitary matrix, when possible.
Fixes the cyclicity detection as reported buggy in https://github.com/Qiskit/qiskit-aqua/issues/1184.

IBM Q Provider 0.11.0¶

Upgrade Notes¶

The deprecated support for running qiskit-ibmq-provider with Python 3.5 has been removed. To use qiskit-ibmq-provider >=0.11.0 you will now need at least Python 3.6. If you are using Python 3.5 the last version which will work is qiskit-ibmq-provider 0.10.x.
Prior to this release, websockets 7.0 was used for Python 3.6. With this release, websockets 8.0 or above is required for all Python versions. The package requirements have been updated to reflect this.

Qiskit 0.22.0¶

Terra 0.15.2¶

No change

Aer 0.6.1¶

No change

Ignis 0.4.0¶

No change

Aqua 0.7.5¶

No change

IBM Q Provider 0.10.0¶

New Features¶

CQC randomness extractors can now be invoked asynchronously, using methods run_async_ext1() and run_async_ext2(). Each of these methods returns a CQCExtractorJob instance that allows you to check on the job status (using status()) and wait for its result (using block_until_ready()). The qiskit.provider.ibmq.random.CQCExtractor.run() method remains synchronous.
You can now use the new IBMQ experiment service to query, retrieve, and download experiment related data. Interface to this service is located in the new qiskit.providers.ibmq.experiment package. Note that this feature is still in beta, and not all accounts have access to it. It is also subject to heavy modification in both functionality and API without backward compatibility.
Two Jupyter magic functions, the IQX dashboard and the backend widget, are updated to display backend reservations. If a backend has reservations scheduled in the next 24 hours, time to the next one and its duration are displayed (e.g. Reservation: in 6 hrs 30 min (60m)). If there is a reservation and the backend is active, the backend status is displayed as active [R].

Upgrade Notes¶

Starting from this release, the basis_gates returned by qiskit.providers.ibmq.IBMQBackend.configuration() may differ for each backend. You should update your program if it relies on the basis gates being ['id','u1','u2','u3','cx']. We recommend always using the configuration() method to find backend configuration values instead of hard coding them.
qiskit-ibmq-provider release 0.10 requires qiskit-terra release 0.15 or above. The package metadata has been updated to reflect the new dependency.

Qiskit 0.21.0¶

Terra 0.15.2¶

No change

Aer 0.6.1¶

No change

Ignis 0.4.0¶

No change

Aqua 0.7.5¶

No change

IBM Q Provider 0.9.0¶

New Features¶

You can now access the IBMQ random number services, such as the CQC randomness extractor, using the new package qiskit.providers.ibmq.random. Note that this feature is still in beta, and not all accounts have access to it. It is also subject to heavy modification in both functionality and API without backward compatibility.

Bug Fixes¶

Fixes an issue that may raise a ValueError if retrieve_job() is used to retrieve a job submitted via the IBM Quantum Experience Composer.
IBMQJobManager has been updated so that if a time out happens while waiting for an old job to finish, the time out error doesn’t prevent a new job to be submitted. Fixes #737

Qiskit 0.20.1¶

Terra 0.15.2¶

Bug Fixes¶

When accessing the definition attribute of a parameterized Gate instance, the generated QuantumCircuit had been generated with an invalid ParameterTable, such that reading from QuantumCircuit.parameters or calling QuantumCircuit.bind_parameters would incorrectly report the unbound parameters. This has been resolved.
SXGate().inverse() had previously returned an “sx_dg” gate with a correct definition but incorrect to_matrix. This has been updated such that SXGate().inverse() returns an SXdgGate() and vice versa.
Instruction.inverse(), when not overridden by a subclass, would in some cases return a Gate instance with an incorrect to_matrix method. The instances of incorrect to_matrix methods have been removed.
For C3XGate with a non-zero angle, inverting the gate via C3XGate.inverse() had previously generated an incorrect inverse gate. This has been corrected.
The MCXGate modes have been updated to return a gate of the same mode when calling .inverse(). This resolves an issue where in some cases, transpiling a circuit containing the inverse of an MCXVChain gate would raise an error.
Previously, when creating a multiply controlled phase gate via PhaseGate.control, an MCU1Gate gate had been returned. This has been had corrected so that an MCPhaseGate is returned.
Previously, attempting to decompose a circuit containing an MCPhaseGate would raise an error due to an inconsistency in the definition of the MCPhaseGate. This has been corrected.
QuantumCircuit.compose and DAGCircuit.compose had, in some cases, incorrectly translated conditional gates if the input circuit contained more than one ClassicalRegister. This has been resolved.
Fixed an issue when creating a qiskit.result.Counts object from an empty data dictionary. Now this will create an empty Counts object. The most_frequent() method is also updated to raise a more descriptive exception when the object is empty. Fixes #5017
Extending circuits with differing registers updated the qregs and cregs properties accordingly, but not the qubits and clbits lists. As these are no longer generated from the registers but are cached lists, this lead to a discrepancy of registers and bits. This has been fixed and the extend method explicitly updates the cached bit lists.
Fix bugs of the concrete implementations of meth:~qiskit.circuit.ControlledGate.inverse method which do not preserve the ctrl_state parameter.
A bug was fixed that caused long pulse schedules to throw a recursion error.

Aer 0.6.1¶

No change

Ignis 0.4.0¶

No change

Aqua 0.7.5¶

No change

IBM Q Provider 0.8.0¶

No change

Qiskit 0.20.0¶

Terra 0.15.1¶

Prelude¶

The 0.15.0 release includes several new features and bug fixes. Some highlights for this release are:

This release includes the introduction of arbitrary basis translation to the transpiler. This includes support for directly targeting a broader range of device basis sets, e.g. backends implementing RZ, RY, RZ, CZ or iSwap gates.

The QuantumCircuit class now tracks global phase. This means controlling a circuit which has global phase now correctly adds a relative phase, and gate matrix definitions are now exact rather than equal up to a global phase.

New Features¶

A new DAG class qiskit.dagcircuit.DAGDependency for representing the dependency form of circuit, In this DAG, the nodes are operations (gates, measure, barrier, etc…) and the edges corresponds to non-commutation between two operations.
Four new functions are added to qiskit.converters for converting back and forth to DAGDependency. These functions are:
- circuit_to_dagdependency() to convert from a QuantumCircuit object to a DAGDependency object.
- dagdependency_to_circuit() to convert from a DAGDependency object to a QuantumCircuit object.
- dag_to_dagdependency() to convert from a DAGCircuit object to a DAGDependency object.
- dagdependency_to_dag() to convert from a DAGDependency object to a DAGCircuit object.
For example:
```
from qiskit.converters.dagdependency_to_circuit import dagdependency_to_circuit
from qiskit import QuantumRegister, ClassicalRegister, QuantumCircuit

circuit_in = QuantumCircuit(2)
circuit_in.h(qr[0])
circuit_in.h(qr[1])

dag_dependency = circuit_to_dagdependency(circuit_in)
circuit_out = dagdepency_to_circuit(dag_dependency)
```
Two new transpiler passes have been added to qiskit.transpiler.passes The first, UnrollCustomDefinitions, unrolls all instructions in the circuit according to their definition property, stopping when reaching either the specified basis_gates or a set of gates in the provided EquivalenceLibrary. The second, BasisTranslator, uses the set of translations in the provided EquivalenceLibrary to re-write circuit instructions in a specified basis.
A new translation_method keyword argument has been added to transpile() to allow selection of the method to be used for translating circuits to the available device gates. For example, transpile(circ, backend, translation_method='translator'). Valid choices are:
- 'unroller': pour utiliser le passe Unroller
- 'translator': to use the BasisTranslator pass.
- 'synthesis': to use the UnitarySynthesis pass.
The default value is 'translator'.
A new class for handling counts result data, qiskit.result.Counts, has been added. This class is a subclass of dict and can be interacted with like any other dictionary. But, it includes helper methods and attributes for dealing with counts results from experiments and also handles post processing and formatting of binary strings at object initialization. A Counts object can be created by passing a dictionary of counts with the keys being either integers, hexadecimal strings of the form '0x4a', binary strings of the form '0b1101', a bit string formatted across register and memory slots (ie '00 10'), or a dit string. For example:
```
from qiskit.result import Counts

counts = Counts({"0x0': 1, '0x1', 3, '0x2': 1020})
```
A new method for constructing qiskit.dagcircuit.DAGCircuit objects has been added, from_networkx(). This method takes in a networkx MultiDiGraph object (in the format returned by to_networkx()) and will return a new DAGCircuit object. The intent behind this function is to enable transpiler pass authors to leverage networkx’s graph algorithm library if a function is missing from the retworkx API. Although, hopefully in such casses an issue will be opened with retworkx issue tracker (or even better a pull request submitted).
A new kwarg for init_qubits has been added to assemble() and execute(). For backends that support this feature init_qubits can be used to control whether the backend executing the circuits inserts any initialization sequences at the start of each shot. By default this is set to True meaning that all qubits can assumed to be in the ground state at the start of each shot. However, when init_qubits is set to False qubits will be uninitialized at the start of each experiment and between shots. Note, that the backend running the circuits has to support this feature for this flag to have any effect.
A new kwarg rep_delay has been added to qiskit.compiler.assemble(), qiskit.execute.execute(), and the constructor for PulseQobjtConfig.qiskit This new kwarg is used to denotes the time between program executions. It must be chosen from the list of valid values set as the rep_delays from a backend’s PulseBackendConfiguration object which can be accessed as backend.configuration().rep_delays).

The rep_delay kwarg will only work on backends which allow for dynamic repetition time. This will also be indicated in the PulseBackendConfiguration object for a backend as the dynamic_reprate_enabled attribute. If dynamic_reprate_enabled is False then the rep_time value specified for qiskit.compiler.assemble(), qiskit.execute.execute(), or the constructor for PulseQobjtConfig will be used rather than rep_delay. rep_time only allows users to specify the duration of a program, rather than the delay between programs.
The qobj_schema.json JSON Schema file in qiskit.schemas has been updated to include the rep_delay as an optional configuration property for pulse qobjs.
The backend_configuration_schema.json JSON Schema file in mod:qiskit.schemas has been updated to include rep_delay_range and default_rep_delay as optional properties for a pulse backend configuration.
A new attribute, global_phase, which is is used for tracking the global phase has been added to the qiskit.circuit.QuantumCircuit class. For example:
```
import math

from qiskit import QuantumCircuit

circ = QuantumCircuit(1, global_phase=math.pi)
circ.u1(0)
```
The global phase may also be changed or queried with circ.global_phase in the above example. In either case the setting is in radians. If the circuit is converted to an instruction or gate the global phase is represented by two single qubit rotations on the first qubit.

This allows for other methods and functions which consume a QuantumCircuit object to take global phase into account. For example. with the global_phase attribute the to_matrix() method for a gate can now exactly correspond to its decompositions instead of just up to a global phase.

The same attribute has also been added to the DAGCircuit class so that global phase can be tracked when converting between QuantumCircuit and DAGCircuit.
Two new classes, AncillaRegister and AncillaQubit have been added to the qiskit.circuit module. These are subclasses of QuantumRegister and Qubit respectively and enable marking qubits being ancillas. This will allow these qubits to be re-used in larger circuits and algorithms.
A new method, control(), has been added to the QuantumCircuit. This method will return a controlled version of the QuantumCircuit object, with both open and closed controls. This functionality had previously only been accessible via the Gate class.
A new method repeat() has been added to the QuantumCircuit class. It returns a new circuit object containing a specified number of repetitions of the original circuit. For example:
from qiskit.circuit import QuantumCircuit qc = QuantumCircuit(2) qc.h(0) qc.cx(0, 1) repeated_qc = qc.repeat(3) repeated_qc.decompose().draw(output='mpl')
The parameters are copied by reference, meaning that if you update the parameters in one instance of the circuit all repetitions will be updated.
A new method reverse_bits() has been added to the QuantumCircuit class. This method will reverse the order of bits in a circuit (both quantum and classical bits). This can be used to switch a circuit from little-endian to big-endian and vice-versa.
A new method, combine_into_edge_map(), was added to the qiskit.transpiler.Layout class. This method enables converting converting two Layout objects into a qubit map for composing two circuits.

A new class, ConfigurableFakeBackend, has been added to the qiskit.test.mock.utils module. This new class enables the creation of configurable mock backends for use in testing. For example:

from qiskit.test.mock.utils import ConfigurableFakeBackend

backend = ConfigurableFakeBackend("Tashkent",
                                  n_qubits=100,
                                  version="0.0.1",
                                  basis_gates=['u1'],
                                  qubit_t1=99.,
                                  qubit_t2=146.,
                                  qubit_frequency=5.,
                                  qubit_readout_error=0.01,
                                  single_qubit_gates=['u1'])

will create a backend object with 100 qubits and all the other parameters specified in the constructor.

A new method draw() has been added to the qiskit.circuit.EquivalenceLibrary class. This method can be used for drawing the contents of an equivalence library, which can be useful for debugging. For example:

from numpy import pi

from qiskit.circuit import EquivalenceLibrary
from qiskit.circuit import QuantumCircuit
from qiskit.circuit import QuantumRegister
from qiskit.circuit import Parameter
from qiskit.circuit.library import HGate
from qiskit.circuit.library import U2Gate
from qiskit.circuit.library import U3Gate

my_equiv_library = EquivalenceLibrary()

q = QuantumRegister(1, 'q')
def_h = QuantumCircuit(q)
def_h.append(U2Gate(0, pi), [q[0]], [])
my_equiv_library.add_equivalence(HGate(), def_h)

theta = Parameter('theta')
phi = Parameter('phi')
lam = Parameter('lam')
def_u2 = QuantumCircuit(q)
def_u2.append(U3Gate(pi / 2, phi, lam), [q[0]], [])
my_equiv_library.add_equivalence(U2Gate(phi, lam), def_u2)

my_equiv_library.draw()

A new Phase instruction, SetPhase, has been added to qiskit.pulse. This instruction sets the phase of the subsequent pulses to the specified phase (in radians. For example:
```
import numpy as np

from qiskit.pulse import DriveChannel
from qiskit.pulse import Schedule
from qiskit.pulse import SetPhase

sched = Schedule()
sched += SetPhase(np.pi, DriveChannel(0))
```
In this example, the phase of the pulses applied to DriveChannel(0) after the SetPhase instruction will be set to \(\pi\) radians.
A new pulse instruction ShiftFrequency has been added to qiskit.pulse.instructions. This instruction enables shifting the frequency of a channel from its set frequency. For example:
```
from qiskit.pulse import DriveChannel
from qiskit.pulse import Schedule
from qiskit.pulse import ShiftFrequency

sched = Schedule()
sched += ShiftFrequency(-340e6, DriveChannel(0))
```
In this example all the pulses applied to DriveChannel(0) after the ShiftFrequency command will have the envelope a frequency decremented by 340MHz.
A new method conjugate() has been added to the ParameterExpression class. This enables calling numpy.conj() without raising an error. Since a ParameterExpression object is real, it will return itself. This behaviour is analogous to Python floats/ints.
A new class PhaseEstimation has been added to qiskit.circuit.library. This circuit library class is the circuit used in the original formulation of the phase estimation algorithm in arXiv:quant-ph/9511026. Phase estimation is the task to to estimate the phase \(\phi\) of an eigenvalue \(e^{2\pi i\phi}\) of a unitary operator \(U\), provided with the corresponding eigenstate \(|psi\rangle\). That is

\[U|\psi\rangle = e^{2\pi i\phi} |\psi\rangle\]

This estimation (and thereby this circuit) is a central routine to several well-known algorithms, such as Shor’s algorithm or Quantum Amplitude Estimation.
The qiskit.visualization function plot_state_qsphere() has a new kwarg show_state_labels which is used to control whether each blob in the qsphere visualization is labeled. By default this kwarg is set to True and shows the basis states next to each blob by default. This feature can be disabled, reverting to the previous behavior, by setting the show_state_labels kwarg to False.
The qiskit.visualization function plot_state_qsphere() has a new kwarg show_state_phases which is set to False by default. When set to True it displays the phase of each basis state.
The qiskit.visualization function plot_state_qsphere() has a new kwarg use_degrees which is set to False by default. When set to True it displays the phase of each basis state in degrees, along with the phase circle at the bottom right.
A new class, QuadraticForm to the qiskit.circuit.library module for implementing a a quadratic form on binary variables. The circuit library element implements the operation

\[|x\rangle |0\rangle \mapsto |x\rangle |Q(x) \mod 2^m\rangle\]

for the quadratic form \(Q\) and \(m\) output qubits. The result is in the \(m\) output qubits is encoded in two’s complement. If \(m\) is not specified, the circuit will choose the minimal number of qubits required to represent the result without applying a modulo operation. The quadratic form is specified using a matrix for the quadratic terms, a vector for the linear terms and a constant offset. If all terms are integers, the circuit implements the quadratic form exactly, otherwise it is only an approximation.

For example:
```
import numpy as np

from qiskit.circuit.library import QuadraticForm

A = np.array([[1, 2], [-1, 0]])
b = np.array([3, -3])
c = -2
m = 4
quad_form_circuit = QuadraticForm(m, A, b, c)
```
Add qiskit.quantum_info.Statevector.expectation_value() and qiskit.quantum_info.DensityMatrix.expectation_value() methods for computing the expectation value of an qiskit.quantum_info.Operator.
For the seed kwarg in the constructor for qiskit.circuit.library.QuantumVolume numpy random Generator objects can now be used. Previously, only integers were a valid input. This is useful when integrating QuantumVolume as part of a larger function with its own random number generation, e.g. generating a sequence of QuantumVolume circuits.

The QuantumCircuit method compose() has a new kwarg front which can be used for prepending the other circuit before the origin circuit instead of appending. For example:

from qiskit.circuit import QuantumCircuit

circ1 = QuantumCircuit(2)
circ2 = QuantumCircuit(2)

circ2.h(0)
circ1.cx(0, 1)

circ1.compose(circ2, front=True).draw(output='mpl')

Two new passes, SabreLayout and SabreSwap for layout and routing have been added to qiskit.transpiler.passes. These new passes are based on the algorithm presented in Li et al., « Tackling the Qubit Mapping Problem for NISQ-Era Quantum Devices », ASPLOS 2019. They can also be selected when using the transpile() function by setting the layout_method kwarg to 'sabre' and/or the routing_method to 'sabre' to use SabreLayout and SabreSwap respectively.
Added the method replace() to the qiskit.pulse.Schedule class which allows a pulse instruction to be replaced with another. For example:
```
.. code-block:: python
```
from qiskit import pulse

d0 = pulse.DriveChannel(0)

sched = pulse.Schedule()

old = pulse.Play(pulse.Constant(100, 1.0), d0) new = pulse.Play(pulse.Constant(100, 0.1), d0)

sched += old

sched = sched.replace(old, new)

assert sched == pulse.Schedule(new)
Added new gate classes to qiskit.circuit.library for the \(\sqrt{X}\), its adjoint \(\sqrt{X}^\dagger\), and controlled \(\sqrt{X}\) gates as SXGate, SXdgGate, and CSXGate. They can also be added to a QuantumCircuit object using the sx(), sxdg(), and csx() respectively.
Add support for Reset instructions to qiskit.quantum_info.Statevector.from_instruction(). Note that this involves RNG sampling in choosing the projection to the zero state in the case where the qubit is in a superposition state. The seed for sampling can be set using the seed() method.

The methods qiskit.circuit.ParameterExpression.subs() and qiskit.circuit.QuantumCircuit.assign_parameters() now accept ParameterExpression as the target value to be substituted.

For example,

from qiskit.circuit import QuantumCircuit, Parameter

p = Parameter('p')
source = QuantumCircuit(1)
source.rz(p, 0)

x = Parameter('x')
source.assign_parameters({p: x*x})

     ┌──────────┐
q_0: ┤ Rz(x**2) ├
     └──────────┘

The QuantumCircuit() method to_gate() has a new kwarg label which can be used to set a label for for the output Gate object. For example:

from qiskit.circuit import QuantumCircuit

circuit_gate = QuantumCircuit(2)
circuit_gate.h(0)
circuit_gate.cx(0, 1)
custom_gate = circuit_gate.to_gate(label='My Special Bell')
new_circ = QuantumCircuit(2)
new_circ.append(custom_gate, [0, 1], [])
new_circ.draw(output='mpl')

Added the UGate, CUGate, PhaseGate, and CPhaseGate with the corresponding QuantumCircuit methods u(), cu(), p(), and cp(). The UGate gate is the generic single qubit rotation gate with 3 Euler angles and the CUGate gate its controlled version. CUGate has 4 parameters to account for a possible global phase of the U gate. The PhaseGate and CPhaseGate gates are the general Phase gate at an arbitrary angle and it’s controlled version.
A new kwarg, cregbundle has been added to the qiskit.visualization.circuit_drawer() function and the QuantumCircuit method draw(). When set to True the cregs will be bundled into a single line in circuit visualizations for the text and mpl drawers. The default value is True. Addresses issue #4290.

For example:
from qiskit import QuantumCircuit circuit = QuantumCircuit(2) circuit.measure_all() circuit.draw(output='mpl', cregbundle=True)
A new kwarg, initial_state has been added to the qiskit.visualization.circuit_drawer() function and the QuantumCircuit method draw(). When set to True the initial state will now be included in circuit visualizations for all drawers. Addresses issue #4293.

For example:
from qiskit import QuantumCircuit circuit = QuantumCircuit(2) circuit.measure_all() circuit.draw(output='mpl', initial_state=True)
Labels will now be displayed when using the “mpl” drawer. There are 2 types of labels - gate labels and control labels. Gate labels will replace the gate name in the display. Control labels will display above or below the controls for a gate. Fixes issues #3766, #4580 Addresses issues #3766 and #4580.

For example:
from qiskit import QuantumCircuit from qiskit.circuit.library.standard_gates import YGate circuit = QuantumCircuit(2) circuit.append(YGate(label='A Y Gate').control(label='Y Control'), [0, 1]) circuit.draw(output='mpl')

Upgrade Notes¶

Implementations of the multi-controlled X Gate ( MCXGrayCode, MCXRecursive, and MCXVChain) have had their name properties changed to more accurately describe their implementation: mcx_gray, mcx_recursive, and mcx_vchain respectively. Previously, these gates shared the name mcx with MCXGate, which caused these gates to be incorrectly transpiled and simulated.
By default the preset passmanagers in qiskit.transpiler.preset_passmanagers are using UnrollCustomDefinitions and BasisTranslator to handle basis changing instead of the previous default Unroller. This was done because the new passes are more flexible and allow targeting any basis set, however the output may differ. To use the previous default you can set the translation_method kwarg on transpile() to 'unroller'.
The qiskit.converters.circuit_to_gate() and :func`qiskit.converters.circuit_to_instruction` converter functions had previously automatically included the generated gate or instruction in the active SessionEquivalenceLibrary. These converters now accept an optional equivalence_library keyword argument to specify if and where the converted instances should be registered. The default behavior has changed to not register the converted instance.
The default value of the cregbundle kwarg for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function has been changed to True. This means that by default the classical bits in the circuit diagram will now be bundled by default, for example:
from qiskit.circuit import QuantumCircuit circ = QuantumCircuit(4) circ.x(0) circ.h(1) circ.measure_all() circ.draw(output='mpl')
If you want to have your circuit drawing retain the previous behavior and show each classical bit in the diagram you can set the cregbundle kwarg to False. For example:
from qiskit.circuit import QuantumCircuit circ = QuantumCircuit(4) circ.x(0) circ.h(1) circ.measure_all() circ.draw(output='mpl', cregbundle=False)
Schedule plotting with qiskit.pulse.Schedule.draw() and qiskit.visualization.pulse_drawer() will no longer display the event table by default. This can be reenabled by setting the table kwarg to True.
The pass RemoveResetInZeroState was previously included in the preset pass manager level_0_pass_manager() which was used with the optimization_level=0 for transpile() and execute() functions. However, RemoveResetInZeroState is an optimization pass and should not have been included in optimization level 0 and was removed. If you need to run transpile() with RemoveResetInZeroState either use a custom pass manager or optimization_level 1, 2, or 3.
The deprecated kwarg line_length for the qiskit.visualization.circuit_drawer() function and qiskit.circuit.QuantumCircuit.draw() method has been removed. It had been deprecated since the 0.10.0 release. Instead you can use the fold kwarg to adjust the width of the circuit diagram.
The 'mpl' output mode for the qiskit.circuit.QuantumCircuit.draw() method and circuit_drawer() now requires the pylatexenc library to be installed. This was already an optional dependency for visualization, but was only required for the 'latex' output mode before. It is now also required for the matplotlib drawer because it is needed to handle correctly sizing gates with matplotlib’s mathtext labels for gates.
The deprecated get_tokens methods for the qiskit.qasm.Qasm and qiskit.qasm.QasmParser has been removed. These methods have been deprecated since the 0.9.0 release. The qiskit.qasm.Qasm.generate_tokens() and qiskit.qasm.QasmParser.generate_tokens() methods should be used instead.
The deprecated kwarg channels_to_plot for qiskit.pulse.Schedule.draw(), qiskit.pulse.Instruction.draw(), qiskit.visualization.pulse.matplotlib.ScheduleDrawer.draw and pulse_drawer() has been removed. The kwarg has been deprecated since the 0.11.0 release and was replaced by the channels kwarg, which functions identically and should be used instead.
The deprecated circuit_instruction_map attribute of the qiskit.providers.models.PulseDefaults class has been removed. This attribute has been deprecated since the 0.12.0 release and was replaced by the instruction_schedule_map attribute which can be used instead.
The union method of Schedule and Instruction have been deprecated since the 0.12.0 release and have now been removed. Use qiskit.pulse.Schedule.insert() and qiskit.pulse.Instruction.meth() methods instead with the kwarg``time=0``.
The deprecated scaling argument to the draw method of Schedule and Instruction has been replaced with scale since the 0.12.0 release and now has been removed. Use the scale kwarg instead.
The deprecated period argument to qiskit.pulse.library functions have been replaced by freq since the 0.13.0 release and now removed. Use the freq kwarg instead of period.

The qiskit.pulse.commands module containing Commands classes was deprecated in the 0.13.0 release and has now been removed. You will have to upgrade your Pulse code if you were still using commands. For example:

Old	New
`Command(args)(channel)`	`Instruction(args, channel)`
Acquire(duration)(AcquireChannel(0))	Acquire(duration, AcquireChannel(0))
Delay(duration)(channel)	Delay(duration, channel)
FrameChange(angle)(DriveChannel(0))	# FrameChange was also renamed ShiftPhase(angle, DriveChannel(0))
Gaussian(...)(DriveChannel(0))	# Pulses need to be `Play`d Play(Gaussian(...), DriveChannel(0))

All classes and function in the qiskit.tool.qi module were deprecated in the 0.12.0 release and have now been removed. Instead use the qiskit.quantum_info module and the new methods and classes that it has for working with quantum states and operators.
The qiskit.quantum_info.basis_state and qiskit.quantum_info.projector functions are deprecated as of Qiskit Terra 0.12.0 as are now removed. Use the qiskit.quantum_info.QuantumState and its derivatives qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix to work with states.
The interactive plotting functions from qiskit.visualization, iplot_bloch_multivector, iplot_state_city, iplot_state_qsphere, iplot_state_hinton, iplot_histogram, iplot_state_paulivec now are just deprecated aliases for the matplotlib based equivalents and are no longer interactive. The hosted static JS code that these functions relied on has been removed and they no longer could work. A normal deprecation wasn’t possible because the site they depended on no longer exists.
The validation components using marshmallow from qiskit.validation have been removed from terra. Since they are no longer used to build any objects in terra.
The marshmallow schema classes in qiskit.result have been removed since they are no longer used by the qiskit.result.Result class.
The output of the to_dict() method for the qiskit.result.Result class is no longer in a format for direct JSON serialization. Depending on the content contained in instances of these classes there may be types that the default JSON encoder doesn’t know how to handle, for example complex numbers or numpy arrays. If you’re JSON serializing the output of the to_dict() method directly you should ensure that your JSON encoder can handle these types.
The option to acquire multiple qubits at once was deprecated in the 0.12.0 release and is now removed. Specifically, the init args mem_slots and reg_slots have been removed from qiskit.pulse.instructions.Acquire, and channel, mem_slot and reg_slot will raise an error if a list is provided as input.
Support for the use of the USE_RETWORKX environment variable which was introduced in the 0.13.0 release to provide an optional fallback to the legacy networkx based qiskit.dagcircuit.DAGCircuit implementation has been removed. This flag was only intended as provide a relief valve for any users that encountered a problem with the new implementation for one release during the transition to retworkx.
The module within qiskit.pulse responsible for schedule->schedule transformations has been renamed from reschedule.py to transforms.py. The previous import path has been deprecated. To upgrade your code:
```
from qiskit.pulse.rescheduler import <X>
```
should be replaced by:
```
from qiskit.pulse.transforms import <X>
```
In previous releases a PassManager did not allow TransformationPass classes to modify the PropertySet. This restriction has been lifted so a TransformationPass class now has read and write access to both the PropertySet and DAGCircuit during run(). This change was made to more efficiently facilitate TransformationPass classes that have an internal state which may be necessary for later passes in the PassManager. Without this change a second redundant AnalysisPass would have been necessary to recreate the internal state, which could add significant overhead.

Deprecation Notes¶

The name of the first positional parameter for the qiskit.visualization functions plot_state_hinton(), plot_bloch_multivector(), plot_state_city(), plot_state_paulivec(), and plot_state_qsphere() has been renamed from rho to state. Passing in the value by name to rho is deprecated and will be removed in a future release. Instead you should either pass the argument positionally or use the new parameter name state.
The qiskit.pulse.pulse_lib module has been deprecated and will be removed in a future release. It has been renamed to qiskit.pulse.library which should be used instead.
The qiskit.circuit.QuantumCircuit method mirror() has been deprecated and will be removed in a future release. The method qiskit.circuit.QuantumCircuit.reverse_ops() should be used instead, since mirroring could be confused with swapping the output qubits of the circuit. The reverse_ops() method only reverses the order of gates that are applied instead of mirroring.
The qubits() and clbits() methods of qiskit.dagcircuit.DAGCircuit have been deprecated and will be removed in a future release. They have been replaced with properties of the same name, qiskit.dagcircuit.DAGCircuit.qubits and qiskit.dagcircuit.DAGCircuit.clbits, and are cached so accessing them is much faster.
The get_sample_pulse method for qiskit.pulse.library.ParametricPulse derived classes (for example GaussianSquare) has been deprecated and will be removed in a future release. It has been replaced by the get_waveform method (for example get_waveform()) which should behave identically.
The use of the optional condition argument on qiskit.dagcircuit.DAGNode, qiskit.dagcircuit.DAGCircuit.apply_operation_back(), and qiskit.dagcircuit.DAGCircuit.apply_operation_front() has been deprecated and will be removed in a future release. Instead the control set in qiskit.circuit.Instruction instances being added to a DAGCircuit should be used.
The set_atol and set_rtol class methods of the qiskit.quantum_info.BaseOperator and qiskit.quantum_info.QuantumState classes (and their subclasses such as Operator and qiskit.quantum_info.DensityMatrix) are deprecated and will be removed in a future release. Instead the value for the attributes .atol and .rtol should be set on the class instead. For example:
```
from qiskit.quantum_info import ScalarOp

ScalarOp.atol = 3e-5
op = ScalarOp(2)
```
The interactive plotting functions from qiskit.visualization, iplot_bloch_multivector, iplot_state_city, iplot_state_qsphere, iplot_state_hinton, iplot_histogram, iplot_state_paulivec have been deprecated and will be removed in a future release. The matplotlib based equivalent functions from qiskit.visualization, plot_bloch_multivector(), plot_state_city(), plot_state_qsphere(), plot_state_hinton(), plot_state_histogram(), and plot_state_paulivec() should be used instead.
The properties acquires, mem_slots, and reg_slots of the qiskit.pulse.instructions.Acquire pulse instruction have been deprecated and will be removed in a future release. They are just duplicates of channel, mem_slot, and reg_slot respectively now that previously deprecated support for using multiple qubits in a single Acquire instruction has been removed.
The SamplePulse class from qiskit.pulse has been renamed to Waveform. SamplePulse is deprecated and will be removed in a future release.
The style dictionary key cregbundle has been deprecated and will be removed in a future release. This has been replaced by the kwarg cregbundle added to the qiskit.visualization.circuit_drawer() function and the QuantumCircuit method draw().

Bug Fixes¶

The qiskit.circuit.QuantumCircuit method num_nonlocal_gates previously included multi-qubit qiskit.circuit.Instruction objects (for example, Barrier) in its count of non-local gates. This has been corrected so that only non-local Gate objects are counted. Fixes #4500
ControlledGate instances with a set ctrl_state were in some cases not being evaluated as equal, even if the compared gates were equivalent. This has been resolved so that Fixes #4573
When accessing a bit from a qiskit.circuit.QuantumRegister or qiskit.circuit.ClassicalRegister by index when using numpy integer types <https://numpy.org/doc/stable/user/basics.types.html>`__ would previously raise a CircuitError exception. This has been resolved so numpy types can be used in addition to Python’s built-in int type. Fixes #3929.
A bug was fixed where only the first qiskit.pulse.configuration.Kernel or qiskit.pulse.configuration.Discriminator for an qiskit.pulse.Acquire was used when there were multiple Acquires at the same time in a qiskit.pulse.Schedule.
The SI unit use for constructing qiskit.pulse.SetFrequency objects is in Hz, but when a PulseQobjInstruction object is created from a SetFrequency instance it needs to be converted to GHz. This conversion was missing from previous releases and has been fixed.
Previously it was possible to set the number of control qubits to zero in which case the the original, potentially non-controlled, operation would be returned. This could cause an AttributeError to be raised if the caller attempted to access an attribute which only ControlledGate object have. This has been fixed by adding a getter and setter for num_ctrl_qubits to validate that a valid value is being used. Fixes #4576
Open controls were implemented by modifying a Gate objects definition. However, when the gate already exists in the basis set, this definition was not used, which resulted in incorrect circuits being sent to a backend after transpilation. This has been fixed by modifying the Unroller pass to use the definition if it encounters a controlled gate with open controls. Fixes #4437
The insert_barriers keyword argument in the ZZFeatureMap class didn’t actually insert barriers in between the Hadamard layers and evolution layers. This has been fixed so that barriers are now properly inserted.
Fixed issue where some gates with three or more qubits would fail to compile in certain instances. Refer to #4577 <https://github.com/Qiskit/qiskit-terra/issues/4577 for more detail.
The matplotlib ('mpl') output backend for the qiskit.circuit.QuantumCircuit method draw() and the qiskit.visualization.circuit_drawer() function was not properly scaling when the kwarg scale was set. Fonts and line widths did not scale with the rest of the image. This has been fixed and all elements of the circuit diagram now scale properly. For example:
from qiskit import QuantumCircuit circuit = QuantumCircuit(2) circuit.h(0) circuit.cx(0, 1) circuit.draw(output='mpl', scale=0.5)
Fixes #4179.
Fixes issue where initializing or evolving qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix classes by circuits by circuit containing Barrier instructions would raise an exception. Fixes #4461
Previously when a QuantumCircuit contained a Gate with a classical condition the transpiler would sometimes fail when using optimization_level=3 on transpile() or execute() raising an UnboundLocalError. This has been fixed by updating the ConsolidateBlocks pass to account for the classical condition. Fixes #4672.
In some situations long gate and register names would overflow, or leave excessive empty space around them when using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function. This has been fixed by using correct text widths for a proportional font. Fixes #4611, #4605, #4545, #4497, #4449, and #3641.
When using the style` kwarg on the :meth:`qiskit.circuit.QuantumCircuit.draw` or :func:`qiskit.visualization.circuit_drawer` with the ``'mpl' output backend the dictionary key 'showindex' set to True, the index numbers at the top of the column did not line up properly. This has been fixed.
When using cregbunde=True with the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function and measuring onto a second fold, the measure arrow would overwrite the creg count. The count was moved to the left to prevent this. Fixes #4148.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function CSwapGate gates and a controlled RZZGate gates now display with their appropriate symbols instead of in a box.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function controlled gates created using the to_gate() method were not properly spaced and could overlap with other gates in the circuit diagram. This issue has been fixed.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function gates with arrays as parameters, such as HamiltonianGate, no longer display with excessive space around them. Fixes #4352.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function generic gates created by directly instantiating qiskit.circuit.Gate method now display the proper background color for the gate. Fixes #4496.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function an AttributeError that occurred when using Isometry or Initialize has been fixed. Fixes #4439.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function some open-controlled gates did not properly display the open controls. This has been corrected so that open controls are properly displayed as open circles. Fixes #4248.
When using the 'mpl' output backend for the qiskit.circuit.QuantumCircuit.draw() method and qiskit.visualization.circuit_drawer() function setting the fold kwarg to -1 will now properly display the circuit without folding. Fixes #4506.
Parametric pulses from qiskit.pulse.library.discrete now have zero ends of parametric pulses by default. The endpoints are defined such that for a function \(f(x)\) then \(f(-1) = f(duration + 1) = 0\). Fixes #4317

Other Notes¶

The qiskit.result.Result class which was previously constructed using the marshmallow library has been refactored to not depend on marshmallow anymore. This new implementation should be a seamless transition but some specific behavior that was previously inherited from marshmallow may not work. Please file issues for any incompatibilities found.

Aer 0.6.1¶

Prelude¶

This 0.6.0 release includes numerous performance improvements for all simulators in the Aer provider and significant changes to the build system when building from source. The main changes are support for SIMD vectorization, approximation in the matrix product state method via bond-dimension truncation, more efficient Pauli expectation value computation, and greatly improved efficiency in Python conversion of C++ result objects. The build system was upgraded to use the Conan to manage common C++ dependencies when building from source.

New Features¶

Add density matrix snapshot support to « statevector » and « statevector_gpu » methods of the QasmSimulator.
Allow density matrix snapshots on specific qubits, not just all qubits. This computes the partial trace of the state over the remaining qubits.
Adds Pauli expectation value snapshot support to the « density_matrix » simulation method of the qiskit.providers.aer.QasmSimulator. Add snapshots to circuits using the qiskit.providers.aer.extensions.SnapshotExpectationValue extension.
Greatly improves performance of the Pauli expectation value snapshot algorithm for the « statevector », « statevector_gpu, « density_matrix », and « density_matrix_gpu » simulation methods of the qiskit.providers.aer.QasmSimulator.
Enable the gate-fusion circuit optimization from the qiskit.providers.aer.QasmSimulator in both the qiskit.providers.aer.StatevectorSimulator and qiskit.providers.aer.UnitarySimulator backends.
Improve the performance of average snapshot data in simulator results. This effects probability, Pauli expectation value, and density matrix snapshots using the following extensions:
Add move constructor and improve memory usage of the C++ matrix class to minimize copies of matrices when moving output of simulators into results.
Improve performance of unitary simulator.
Add approximation to the « matrix_product_state » simulation method of the QasmSimulator to limit the bond-dimension of the MPS.

There are two modes of approximation. Both discard the smallest Schmidt coefficients following the SVD algorithm. There are two parameters that control the degree of approximation: "matrix_product_state_max_bond_dimension" (int): Sets a limit on the number of Schmidt coefficients retained at the end of the svd algorithm. Coefficients beyond this limit will be discarded. (Default: None, i.e., no limit on the bond dimension). "matrix_product_state_truncation_threshold" (double): Discard the smallest coefficients for which the sum of their squares is smaller than this threshold. (Default: 1e-16).
Improve the performance of measure sampling when using the « matrix_product_state » QasmSimulator simulation method.
Add support for Delay, Phase and SetPhase pulse instructions to the qiskit.providers.aer.PulseSimulator.
Improve the performance of the qiskit.providers.aer.PulseSimulator by caching calls to RHS function
Introduce alternate DE solving methods, specifiable through backend_options in the qiskit.providers.aer.PulseSimulator.
Improve performance of simulator result classes by using move semantics and removing unnecessary copies that were happening when combining results from separate experiments into the final result object.
Greatly improve performance of pybind11 conversion of simulator results by using move semantics where possible, and by moving vector and matrix results to Numpy arrays without copies.
Change the RNG engine for simulators from 32-bit Mersenne twister to 64-bit Mersenne twister engine.
Improves the performance of the « statevector » simulation method of the qiskit.providers.aer.QasmSimulator and qiskit.providers.aer.StatevectorSimulator by using SIMD intrinsics on systems that support the AVX2 instruction set. AVX2 support is automatically detected and enabled at runtime.

Upgrade Notes¶

Changes the build system to use the Conan package manager. This tool will handle most of the dependencies needed by the C++ source code. Internet connection may be needed for the first build or when dependencies are added or updated, in order to download the required packages if they are not in your Conan local repository.

When building the standalone version of qiskit-aer you must install conan first with:
```
pip install conan
```
Changes how transpilation passes are handled in the C++ Controller classes so that each pass must be explicitly called. This allows for greater customization on when each pass should be called, and with what parameters. In particular this enables setting different parameters for the gate fusion optimization pass depending on the QasmController simulation method.
Add gate_length_units kwarg to qiskit.providers.aer.noise.NoiseModel.from_device() for specifying custom gate_lengths in the device noise model function to handle unit conversions for internal code.
Add Controlled-Y (« cy ») gate to the Stabilizer simulator methods supported gateset.
For Aer’s backend the jsonschema validation of input qobj objects from terra is now opt-in instead of being enabled by default. If you want to enable jsonschema validation of qobj set the validate kwarg on the qiskit.providers.aer.QasmSimualtor.run() method for the backend object to True.
Adds an OpSet object to the base simulator State class to allow easier validation of instructions, gates, and snapshots supported by simulators.
Refactor OpSet class. Moved OpSet to separate header file and add contains and difference methods based on std::set::contains and std::algorithm::set_difference. These replace the removed invalid and validate instructions from OpSet, but with the order reversed. It returns a list of other ops not in current opset rather than opset instructions not in the other.
Improves how measurement sampling optimization is checked. The expensive part of this operation is now done once during circuit construction where rather than multiple times during simulation for when checking memory requirements, simulation method, and final execution.

Bug Fixes¶

Remove « extended_stabilizer » from the automatically selected simulation methods. This is needed as the extended stabilizer method is not exact and may give incorrect results for certain circuits unless the user knows how to optimize its configuration parameters.

The automatic method now only selects from « stabilizer », « density_matrix », and « statevector » methods. If a non-Clifford circuit that is too large for the statevector method is executed an exception will be raised suggesting you could try explicitly using the « extended_stabilizer » or « matrix_product_state » methods instead.
Disables gate fusion for the matrix product state simulation method as this was causing issues with incorrect results being returned in some cases.
Fixes a bug causing incorrect channel evaluation in the qiskit.providers.aer.PulseSimulator.
Fixes several minor bugs for Hamiltonian parsing edge cases in the qiskit.providers.aer.pulse.system_models.hamiltonian_model.HamiltonianModel class.

Ignis 0.4.0¶

Prelude¶

The main change made in this release is a refactor of the Randomized Benchmarking code to integrate the updated Clifford class qiskit.quantum_info.Clifford from Terra and to improve the CNOT-Dihedral class.

New Features¶

The qiskit.ignis.verification.randomized_benchmarking.randomized_benchmarking_seq() function was refactored to use the updated Clifford class Clifford, to allow efficient Randomized Benchmarking (RB) on Clifford sequences with more than 2 qubits. In addition, the code of the CNOT-Dihedral class qiskit.ignis.verification.randomized_benchmarking.CNOTDihedral was refactored to make it more efficient, by using numpy arrays, as well not using pre-generated pickle files storing all the 2-qubit group elements. The qiskit.ignis.verification.randomized_benchmarking.randomized_benchmarking_seq() function has a new kwarg rand_seed which can be used to specify a seed for the random number generator used to generate the RB circuits. This can be useful for having a reproducible circuit.
The qiskit.ignis.verification.qv_circuits() function has a new kwarg seed which can be used to specify a seed for the random number generator used to generate the Quantum Volume circuits. This can be useful for having a reproducible circuit.

Upgrade Notes¶

The qiskit.ignis.verification.randomized_benchmarking.randomized_benchmarking_seq() function is now using the updated Clifford class Clifford and the updated CNOT-Dihedral class qiskit.ignis.verification.randomized_benchmarking.CNOTDihedral to construct its output instead of using pre-generated group tables for the Clifford and CNOT-Dihedral group elements, which were stored in pickle files. This may result in subtle differences from the output from the previous version.
A new requirement scikit-learn has been added to the requirements list. This dependency was added in the 0.3.0 release but wasn’t properly exposed as a dependency in that release. This would lead to an ImportError if the qiskit.ignis.measurement.discriminator.iq_discriminators module was imported. This is now correctly listed as a dependency so that scikit-learn will be installed with qiskit-ignis.
The qiskit.ignis.verification.qv_circuits() function is now using the circuit library class QuantumVolume to construct its output instead of building the circuit from scratch. This may result in subtle differences from the output from the previous version.
Tomography fitters can now also get list of Result objects instead of a single Result as requested in issue #320.

Deprecation Notes¶

The kwarg interleaved_gates for the qiskit.ignis.verification.randomized_benchmarking.randomized_benchmarking_seq() function has been deprecated and will be removed in a future release. It is superseded by interleaved_elem. The helper functions qiskit.ignis.verification.randomized_benchmarking.BasicUtils, qiskit.ignis.verification.randomized_benchmarking.CliffordUtils and qiskit.ignis.verification.randomized_benchmarking.DihedralUtils were deprecated. These classes are superseded by qiskit.ignis.verification.randomized_benchmarking.RBgroup that handles the group operations needed for RB. The class qiskit.ignis.verification.randomized_benchmarking.Clifford is superseded by Clifford.
The kwargs qr and cr for the qiskit.ignis.verification.qv_circuits() function have been deprecated and will be removed in a future release. These kwargs were documented as being used for specifying a qiskit.circuit.QuantumRegister and qiskit.circuit.ClassicalRegister to use in the generated Quantum Volume circuits instead of creating new ones. However, the parameters were never actually respected and a new Register would always be created regardless of whether they were set or not. This behavior is unchanged and these kwargs still do not have any effect, but are being deprecated prior to removal to avoid a breaking change for users who may have been setting either.
Support for passing in subsets of qubits as a list in the qubit_lists parameter for the qiskit.ignis.verification.qv_circuits() function has been deprecated and will removed in a future release. In the past this was used to specify a layout to run the circuit on a device. In other words if you had a 5 qubit device and wanted to run a 2 qubit QV circuit on qubits 1, 3, and 4 of that device. You would pass in [1, 3, 4] as one of the lists in qubit_lists, which would generate a 5 qubit virtual circuit and have qv applied to qubits 1, 3, and 4 in that virtual circuit. However, this functionality is not necessary and overlaps with the concept of initial_layout in the transpiler and whether a circuit has been embedded with a layout set. Moving forward instead you should just run transpile() or execute() with initial layout set to do this. For example, running the above example would become:
```
from qiskit import execute
from qiskit.ignis.verification import qv_circuits

initial_layout = [1, 3, 4]
qv_circs, _ = qv_circuits([list(range3)])
execute(qv_circuits, initial_layout=initial_layout)
```

Bug Fixes¶

Fix a bug of the position of measurement pulses inserted by py:func:qiskit.ignis.characterization.calibrations.pulse_schedules.drag_schedules. Fixes #465

Aqua 0.7.5¶

New Features¶

Removed soft dependency on CPLEX in ADMMOptimizer. Now default optimizers used by ADMMOptimizer are MinimumEigenOptimizer for QUBO problems and SlsqpOptimizer as a continuous optimizer. You can still use CplexOptimizer as an optimizer for ADMMOptimizer, but it should be set explicitly.
New Yahoo! finance provider created.
Introduced QuadraticProgramConverter which is an abstract class for converters. Added convert/interpret methods for converters instead of encode/decode. Added to_ising and from_ising to QuadraticProgram class. Moved all parameters from convert to constructor except name. Created setter/getter for converter parameters. Added auto_define_penalty and interpret for``LinearEqualityToPenalty``. Now error messages of converters are more informative.
Added an SLSQP optimizer qiskit.optimization.algorithms.SlsqpOptimizer as a wrapper of the corresponding SciPy optimization method. This is a classical optimizer, does not depend on quantum algorithms and may be used as a replacement for CobylaOptimizer.
Cobyla optimizer has been modified to accommodate a multi start feature introduced in the SLSQP optimizer. By default, the optimizer does not run in the multi start mode.
The SummedOp does a mathematically more correct check for equality, where expressions such as X + X == 2*X and X + Z == Z + X evaluate to True.

Deprecation Notes¶

GSLS optimizer class deprecated __init__ parameter max_iter in favor of maxiter. SPSA optimizer class deprecated __init__ parameter max_trials in favor of maxiter. optimize_svm function deprecated max_iters parameter in favor of maxiter. ADMMParameters class deprecated __init__ parameter max_iter in favor of maxiter.
The ising convert classes qiskit.optimization.converters.QuadraticProgramToIsing and qiskit.optimization.converters.IsingToQuadraticProgram have been deprecated and will be removed in a future release. Instead the qiskit.optimization.QuadraticProgram methods to_ising() and from_ising() should be used instead.
The pprint_as_string method for qiskit.optimization.QuadraticProgram has been deprecated and will be removed in a future release. Instead you should just run .pprint_as_string() on the output from to_docplex()
The prettyprint method for qiskit.optimization.QuadraticProgram has been deprecated and will be removed in a future release. Instead you should just run .prettyprint() on the output from to_docplex()

Bug Fixes¶

Changed in python version 3.8: On macOS, the spawn start method is now the default. The fork start method should be considered unsafe as it can lead to crashes in subprocesses. However P_BFGS doesn’t support spawn, so we revert to single process. Refer to #1109 <https://github.com/Qiskit/qiskit-aqua/issues/1109> for more details.
Binding parameters in the CircuitStateFn did not copy the value of is_measurement and always set is_measurement=False. This has been fixed.
Previously, SummedOp.to_matrix_op built a list MatrixOp’s (with numpy matrices) and then summed them, returning a single MatrixOp. Some algorithms (for example vqe) require summing thousands of matrices, which exhausts memory when building the list of matrices. With this change, no list is constructed. Rather, each operand in the sum is converted to a matrix, added to an accumulator, and discarded.
Changing backends in VQE from statevector to qasm_simulator or real device was causing an error due to CircuitSampler incompatible reuse. VQE was changed to always create a new CircuitSampler and create a new expectation in case not entered by user. Refer to #1153 <https://github.com/Qiskit/qiskit-aqua/issues/1153> for more details.
Exchange and Wikipedia finance providers were fixed to correctly handle Quandl data. Refer to #775 <https://github.com/Qiskit/qiskit-aqua/issues/775> for more details. Fixes a divide by 0 error on finance providers mean vector and covariance matrix calculations. Refer to #781 <https://github.com/Qiskit/qiskit-aqua/issues/781> for more details.
The ListOp.combo_fn property has been lost in several transformations, such as converting to another operator type, traversing, reducing or multiplication. Now this attribute is propagated to the resulting operator.
The evaluation of some operator expressions, such as of SummedOp``s and evaluations with the ``CircuitSampler did not treat coefficients correctly or ignored them completely. E.g. evaluating ~StateFn(0 * (I + Z)) @ Plus did not yield 0 or the normalization of ~StateFn(I) @ ((Plus + Minus) / sqrt(2)) missed a factor of sqrt(2). This has been fixed.
OptimizationResult included some public setters and class variables were Optional. This fix makes all class variables read-only so that mypy and pylint can check types more effectively. MinimumEigenOptimizer.solve generated bitstrings in a result as str. This fix changed the result into List[float] as the other algorithms do. Some public classes related to optimization algorithms were missing in the documentation of qiskit.optimization.algorithms. This fix added all such classes to the docstring. #1131 <https://github.com/Qiskit/qiskit-aqua/issues/1131> for more details.
OptimizationResult.__init__ did not check whether the sizes of x and variables match or not (they should match). This fix added the check to raise an error if they do not match and fixes bugs detected by the check. This fix also adds missing unit tests related to OptimizationResult.variable_names and OptimizationResult.variables_dict in test_converters. #1167 <https://github.com/Qiskit/qiskit-aqua/issues/1167> for more details.
Fix parameter binding in the OperatorStateFn, which did not bind parameters of the underlying primitive but just the coefficients.
op.eval(other), where op is of type OperatorBase, sometimes silently returns a nonsensical value when the number of qubits in op and other are not equal. This fix results in correct behavior, which is to throw an error rather than return a value, because the input in this case is invalid.
The construct_circuit method of VQE previously returned the expectation value to be evaluated as type OperatorBase. This functionality has been moved into construct_expectation and construct_circuit returns a list of the circuits that are evaluated to compute the expectation value.

IBM Q Provider 0.8.0¶

New Features¶

IBMQBackend now has a new reservations() method that returns reservation information for the backend, with optional filtering. In addition, you can now use provider.backends.my_reservations() to query for your own reservations.
qiskit.providers.ibmq.job.IBMQJob.result() raises an IBMQJobFailureError exception if the job has failed. The exception message now contains the reason the job failed, if the entire job failed for a single reason.
A new attribute client_version was added to IBMQJob and qiskit.result.Result object retrieved via qiskit.providers.ibmq.job.IBMQJob.result(). client_version is a dictionary with the key being the name and the value being the version of the client used to submit the job, such as Qiskit.
The least_busy() function now takes a new, optional parameter reservation_lookahead. If specified or defaulted to, a backend is considered unavailable if it has reservations in the next n minutes, where n is the value of reservation_lookahead. For example, if the default value of 60 is used, then any backends that have reservations in the next 60 minutes are considered unavailable.
ManagedResults now has a new combine_results() method that combines results from all managed jobs and returns a single Result object. This Result object can be used, for example, in qiskit-ignis fitter methods.

Upgrade Notes¶

Timestamps in the following fields are now in local time instead of UTC:
- Backend properties returned by qiskit.providers.ibmq.IBMQBackend.properties().
- Backend properties returned by qiskit.providers.ibmq.job.IBMQJob.properties().
- estimated_start_time and estimated_complete_time in QueueInfo, returned by qiskit.providers.ibmq.job.IBMQJob.queue_info().
- date in Result, returned by qiskit.providers.ibmq.job.IBMQJob.result().
In addition, the datetime parameter for qiskit.providers.ibmq.IBMQBackend.properties() is also expected to be in local time unless it has UTC timezone information.
websockets 8.0 or above is now required if Python 3.7 or above is used. websockets 7.0 will continue to be used for Python 3.6 or below.
On Windows, the event loop policy is set to WindowsSelectorEventLoopPolicy instead of using the default WindowsProactorEventLoopPolicy. This fixes the issue that the qiskit.providers.ibmq.job.IBMQJob.result() method could hang on Windows. Fixes #691

Deprecation Notes¶

Use of Qconfig.py to save IBM Quantum Experience credentials is deprecated and will be removed in the next release. You should use qiskitrc (the default) instead.

Bug Fixes¶

Fixes an issue wherein a call to qiskit.providers.ibmq.IBMQBackend.jobs() can hang if the number of jobs being returned is large. Fixes #674
Fixes an issue which would raise a ValueError when building error maps in Jupyter for backends that are offline. Fixes #706
qiskit.providers.ibmq.IBMQBackend.jobs() will now return the correct list of IBMQJob objects when the status kwarg is set to 'RUNNING'.
The package metadata has been updated to properly reflect the dependency on qiskit-terra >= 0.14.0. This dependency was implicitly added as part of the 0.7.0 release but was not reflected in the package requirements so it was previously possible to install qiskit-ibmq-provider with a version of qiskit-terra which was too old. Fixes #677

Qiskit 0.19.6¶

Terra 0.14.2¶

No Change

Aer 0.5.2¶

No Change

Ignis 0.3.3¶

Upgrade Notes¶

A new requirement scikit-learn has been added to the requirements list. This dependency was added in the 0.3.0 release but wasn’t properly exposed as a dependency in that release. This would lead to an ImportError if the qiskit.ignis.measurement.discriminator.iq_discriminators module was imported. This is now correctly listed as a dependency so that scikit-learn will be installed with qiskit-ignis.

Bug Fixes¶

Fixes an issue in qiskit-ignis 0.3.2 which would raise an ImportError when qiskit.ignis.verification.tomography.fitters.process_fitter was imported without cvxpy being installed.

Aqua 0.7.3¶

No Change

IBM Q Provider 0.7.2¶

No Change

Qiskit 0.19.5¶

Terra 0.14.2¶

No Change

Aer 0.5.2¶

No Change

Ignis 0.3.2¶

Bug Fixes¶

The qiskit.ignis.verification.TomographyFitter.fit() method has improved detection logic for the default fitter. Previously, the cvx fitter method was used whenever cvxpy was installed. However, it was possible to install cvxpy without an SDP solver that would work for the cvx fitter method. This logic has been reworked so that the cvx fitter method is only used if cvxpy is installed and an SDP solver is present that can be used. Otherwise, the lstsq fitter is used.
Fixes an edge case in qiskit.ignis.mitigation.measurement.fitters.MeasurementFitter.apply() for input that has invalid or incorrect state labels that don’t match the calibration circuit. Previously, this would not error and just return an empty result. Instead now this case is correctly caught and a QiskitError exception is raised when using incorrect labels.

Aqua 0.7.3¶

Upgrade Notes¶

The cvxpy dependency which is required for the svm classifier has been removed from the requirements list and made an optional dependency. This is because installing cvxpy is not seamless in every environment and often requires a compiler be installed to run. To use the svm classifier now you’ll need to install cvxpy by either running pip install cvxpy<1.1.0 or to install it with aqua running pip install qiskit-aqua[cvx].

Bug Fixes¶

The compose method of the CircuitOp used QuantumCircuit.combine which has been changed to use QuantumCircuit.compose. Using combine leads to the problem that composing an operator with a CircuitOp based on a named register does not chain the operators but stacks them. E.g. composing Z ^ 2 with a circuit based on a 2-qubit named register yielded a 4-qubit operator instead of a 2-qubit operator.
The MatrixOp.to_instruction method previously returned an operator and not an instruction. This method has been updated to return an Instruction. Note that this only works if the operator primitive is unitary, otherwise an error is raised upon the construction of the instruction.
The __hash__ method of the PauliOp class used the id() method which prevents set comparisons to work as expected since they rely on hash tables and identical objects used to not have identical hashes. Now, the implementation uses a hash of the string representation inline with the implementation in the Pauli class.

IBM Q Provider 0.7.2¶

No Change

Qiskit 0.19.4¶

Terra 0.14.2¶

Upgrade Notes¶

The circuit_to_gate and circuit_to_instruction converters had previously automatically included the generated gate or instruction in the active SessionEquivalenceLibrary. These converters now accept an optional equivalence_library keyword argument to specify if and where the converted instances should be registered. The default behavior is not to register the converted instance.

Bug Fixes¶

Implementations of the multi-controlled X Gate (MCXGrayCode, MCXRecursive and MCXVChain) have had their name properties changed to more accurately describe their implementation (mcx_gray, mcx_recursive, and mcx_vchain respectively.) Previously, these gates shared the name mcx` with ``MCXGate, which caused these gates to be incorrectly transpiled and simulated.
ControlledGate instances with a set ctrl_state were in some cases not being evaluated as equal, even if the compared gates were equivalent. This has been resolved.
Fixed the SI unit conversion for qiskit.pulse.SetFrequency. The SetFrequency instruction should be in Hz on the frontend and has to be converted to GHz when SetFrequency is converted to PulseQobjInstruction.
Open controls were implemented by modifying a gate's definition. However, when the gate already exists in the basis, this definition is not used, which yields incorrect circuits sent to a backend. This modifies the unroller to output the definition if it encounters a controlled gate with open controls.

Aer 0.5.2¶

No Change

Ignis 0.3.0¶

No Change

Aqua 0.7.2¶

Prelude¶

VQE expectation computation with Aer qasm_simulator now defaults to a computation that has the expected shot noise behavior.

Upgrade Notes¶

cvxpy is now in the requirements list as a dependency for qiskit-aqua. It is used for the quadratic program solver which is used as part of the qiskit.aqua.algorithms.QSVM. Previously cvxopt was an optional dependency that needed to be installed to use this functionality. This is no longer required as cvxpy will be installed with qiskit-aqua.
For state tomography run as part of qiskit.aqua.algorithms.HHL with a QASM backend the tomography fitter function qiskit.ignis.verification.StateTomographyFitter.fit() now gets called explicitly with the method set to lstsq to always use the least-squares fitting. Previously it would opportunistically try to use the cvx fitter if cvxpy were installed. But, the cvx fitter depends on a specifically configured cvxpy installation with an SDP solver installed as part of cvxpy which is not always present in an environment with cvxpy installed.
The VQE expectation computation using qiskit-aer’s qiskit.providers.aer.extensions.SnapshotExpectationValue instruction is not enabled by default anymore. This was changed to be the default in 0.7.0 because it is significantly faster, but it led to unexpected ideal results without shot noise (see #1013 for more details). The default has now changed back to match user expectations. Using the faster expectation computation is now opt-in by setting the new include_custom kwarg to True on the qiskit.aqua.algorithms.VQE constructor.

New Features¶

A new kwarg include_custom has been added to the constructor for qiskit.aqua.algorithms.VQE and it’s subclasses (mainly qiskit.aqua.algorithms.QAOA). When set to true and the expectation kwarg is set to None (the default) this will enable the use of VQE expectation computation with Aer’s qasm_simulator qiskit.providers.aer.extensions.SnapshotExpectationValue instruction. The special Aer snapshot based computation is much faster but with the ideal output similar to state vector simulator.

IBM Q Provider 0.7.2¶

No Change

Qiskit 0.19.3¶

Terra 0.14.1¶

No Change

Aer 0.5.2¶

Bug Fixes¶

Fixed bug with statevector and unitary simulators running a number of (parallel) shots equal to the number of CPU threads instead of only running a single shot.
Fixes the « diagonal » qobj gate instructions being applied incorrectly in the density matrix Qasm Simulator method.
Fixes bug where conditional gates were not being applied correctly on the density matrix simulation method.
Fix bug in CZ gate and Z gate for « density_matrix_gpu » and « density_matrix_thrust » QasmSimulator methods.
Fixes issue where memory requirements of simulation were not being checked on the QasmSimulator when using a non-automatic simulation method.
Fixed a memory leak that effected the GPU simulator methods

Ignis 0.3.0¶

No Change

Aqua 0.7.1¶

No Change

IBM Q Provider 0.7.2¶

Bug Fixes¶

qiskit.provider.ibmq.IBMQBackend.jobs() will now return the correct list of IBMQJob objects when the status kwarg is set to 'RUNNING'. Fixes #523
The package metadata has been updated to properly reflect the dependency on qiskit-terra >= 0.14.0. This dependency was implicitly added as part of the 0.7.0 release but was not reflected in the package requirements so it was previously possible to install qiskit-ibmq-provider with a version of qiskit-terra which was too old. Fixes #677

Qiskit 0.19.0¶

Terra 0.14.0¶

Prelude¶

The 0.14.0 release includes several new features and bug fixes. The biggest change for this release is the introduction of a quantum circuit library in qiskit.circuit.library, containing some circuit families of interest.

The circuit library gives users access to a rich set of well-studied circuit families, instances of which can be used as benchmarks, as building blocks in building more complex circuits, or as a tool to explore quantum computational advantage over classical. The contents of this library will continue to grow and mature.

The initial release of the circuit library contains:

standard_gates: these are fixed-width gates commonly used as primitive building blocks, consisting of 1, 2, and 3 qubit gates. For example the XGate, RZZGate and CSWAPGate. The old location of these gates under qiskit.extensions.standard is deprecated.
generalized_gates: these are families that can generalize to arbitrarily many qubits, for example a Permutation or GMS (Global Molmer-Sorensen gate).
boolean_logic: circuits that transform basis states according to simple Boolean logic functions, such as ADD or XOR.
arithmetic: a set of circuits for doing classical arithmetic such as WeightedAdder and IntegerComparator.
basis_changes: circuits such as the quantum Fourier transform, QFT, that mathematically apply basis changes.
n_local: patterns to easily create large circuits with rotation and entanglement layers, such as TwoLocal which uses single-qubit rotations and two-qubit entanglements.
data_preparation: circuits that take classical input data and encode it in a quantum state that is difficult to simulate, e.g. PauliFeatureMap or ZZFeatureMap.
Other circuits that have proven interesting in the literature, such as QuantumVolume, GraphState, or IQP.

To allow easier use of these circuits as building blocks, we have introduced a compose() method of qiskit.circuit.QuantumCircuit for composition of circuits either with other circuits (by welding them at the ends and optionally permuting wires) or with other simpler gates:

>>> lhs.compose(rhs, qubits=[3, 2], inplace=True)

            ┌───┐                   ┌─────┐                ┌───┐
lqr_1_0: ───┤ H ├───    rqr_0: ──■──┤ Tdg ├    lqr_1_0: ───┤ H ├───────────────
            ├───┤              ┌─┴─┐└─────┘                ├───┤
lqr_1_1: ───┤ X ├───    rqr_1: ┤ X ├───────    lqr_1_1: ───┤ X ├───────────────
         ┌──┴───┴──┐           └───┘                    ┌──┴───┴──┐┌───┐
lqr_1_2: ┤ U1(0.1) ├  +                     =  lqr_1_2: ┤ U1(0.1) ├┤ X ├───────
         └─────────┘                                    └─────────┘└─┬─┘┌─────┐
lqr_2_0: ─────■─────                           lqr_2_0: ─────■───────■──┤ Tdg ├
            ┌─┴─┐                                          ┌─┴─┐        └─────┘
lqr_2_1: ───┤ X ├───                           lqr_2_1: ───┤ X ├───────────────
            └───┘                                          └───┘
lcr_0: 0 ═══════════                           lcr_0: 0 ═══════════════════════
lcr_1: 0 ═══════════                           lcr_1: 0 ═══════════════════════

With this, Qiskit’s circuits no longer assume an implicit initial state of \(|0\rangle\), and will not be drawn with this initial state. The all-zero initial state is still assumed on a backend when a circuit is executed.

New Features¶

A new method, has_entry(), has been added to the qiskit.circuit.EquivalenceLibrary class to quickly check if a given gate has any known decompositions in the library.
A new class IQP, to construct an instantaneous quantum polynomial circuit, has been added to the circuit library module qiskit.circuit.library.
A new compose() method has been added to qiskit.circuit.QuantumCircuit. It allows composition of two quantum circuits without having to turn one into a gate or instruction. It also allows permutations of qubits/clbits at the point of composition, as well as optional inplace modification. It can also be used in place of append(), as it allows composing instructions and operators onto the circuit as well.
qiskit.circuit.library.Diagonal circuits have been added to the circuit library. These circuits implement diagonal quantum operators (consisting of non-zero elements only on the diagonal). They are more efficiently simulated by the Aer simulator than dense matrices.
Add from_label() method to the qiskit.quantum_info.Clifford class for initializing as the tensor product of single-qubit I, X, Y, Z, H, or S gates.

Schedule transformer qiskit.pulse.reschedule.compress_pulses() performs an optimization pass to reduce the usage of waveform memory in hardware by replacing multiple identical instances of a pulse in a pulse schedule with a single pulse. For example:

from qiskit.pulse import reschedule

schedules = []
for _ in range(2):
    schedule = Schedule()
    drive_channel = DriveChannel(0)
    schedule += Play(SamplePulse([0.0, 0.1]), drive_channel)
    schedule += Play(SamplePulse([0.0, 0.1]), drive_channel)
    schedules.append(schedule)

compressed_schedules = reschedule.compress_pulses(schedules)

The qiskit.transpiler.Layout has a new method reorder_bits() that is used to reorder a list of virtual qubits based on the layout object.
Two new methods have been added to the qiskit.providers.models.PulseBackendConfiguration for interacting with channels.
- get_channel_qubits() to get a list of all qubits operated by the given channel and
- get_qubit_channel() to get a list of channels operating on the given qubit.
New qiskit.extensions.HamiltonianGate and qiskit.circuit.QuantumCircuit.hamiltonian() methods are introduced, representing Hamiltonian evolution of the circuit wavefunction by a user-specified Hermitian Operator and evolution time. The evolution time can be a Parameter, allowing the creation of parameterized UCCSD or QAOA-style circuits which compile to UnitaryGate objects if time parameters are provided. The Unitary of a HamiltonianGate with Hamiltonian Operator H and time parameter t is \(e^{-iHt}\).
The circuit library module qiskit.circuit.library now provides a new boolean logic AND circuit, qiskit.circuit.library.AND, and OR circuit, qiskit.circuit.library.OR, which implement the respective operations on a variable number of provided qubits.
New fake backends are added under qiskit.test.mock. These include mocked versions of ibmq_armonk, ibmq_essex, ibmq_london, ibmq_valencia, ibmq_cambridge, ibmq_paris, ibmq_rome, and ibmq_athens. As with other fake backends, these include snapshots of calibration data (i.e. backend.defaults()) and error data (i.e. backend.properties()) taken from the real system, and can be used for local testing, compilation and simulation.
The last_update_date parameter for BackendProperties can now also be passed in as a datetime object. Previously only a string in ISO8601 format was accepted.
Adds qiskit.quantum_info.Statevector.from_int() and qiskit.quantum_info.DensityMatrix.from_int() methods that allow constructing a computational basis state for specified system dimensions.
The methods on the qiskit.circuit.QuantumCircuit class for adding gates (for example h()) which were previously added dynamically at run time to the class definition have been refactored to be statically defined methods of the class. This means that static analyzer (such as IDEs) can now read these methods.

Upgrade Notes¶

A new package, python-dateutil, is now required and has been added to the requirements list. It is being used to parse datetime strings received from external providers in BackendProperties objects.
The marshmallow schema classes in qiskit.providers.models have been removed since they are no longer used by the BackendObjects.
The output of the to_dict() method for the classes in qiskit.providers.models is no longer in a format for direct JSON serialization. Depending on the content contained in instances of these class there may be numpy arrays and/or complex numbers in the fields of the dict. If you’re JSON serializing the output of the to_dict methods you should ensure your JSON encoder can handle numpy arrays and complex numbers. This includes:
- qiskit.providers.models.BackendConfiguration.to_dict()
- qiskit.providers.models.BackendProperties.to_dict()
- qiskit.providers.models.BackendStatus.to_dict()
- qiskit.providers.models.QasmBackendConfiguration.to_dict()
- qiskit.providers.models.PulseBackendConfiguration.to_dict()
- qiskit.providers.models.UchannelLO.to_dict()
- qiskit.providers.models.GateConfig.to_dict()
- qiskit.providers.models.PulseDefaults.to_dict()
- qiskit.providers.models.Command.to_dict()
- qiskit.providers.models.JobStatus.to_dict()
- qiskit.providers.models.Nduv.to_dict()
- qiskit.providers.models.Gate.to_dict()

Deprecation Notes¶

The qiskit.dagcircuit.DAGCircuit.compose() method now takes a list of qubits/clbits that specify the positional order of bits to compose onto. The dictionary-based method of mapping using the edge_map argument is deprecated and will be removed in a future release.
The combine_into_edge_map() method for the qiskit.transpiler.Layout class has been deprecated and will be removed in a future release. Instead, the new method reorder_bits() should be used to reorder a list of virtual qubits according to the layout object.
Passing a qiskit.pulse.ControlChannel object in via the parameter channel for the qiskit.providers.models.PulseBackendConfiguration method control() has been deprecated and will be removed in a future release. The ControlChannel objects are now generated from the backend configuration channels attribute which has the information of all channels and the qubits they operate on. Now, the method control() is expected to take the parameter qubits of the form (control_qubit, target_qubit) and type list or tuple, and returns a list of control channels.
The AND and OR methods of qiskit.circuit.QuantumCircuit are deprecated and will be removed in a future release. Instead you should use the circuit library boolean logic classes qiskit.circuit.library.AND amd qiskit.circuit.library.OR and then append those objects to your class. For example:
```
from qiskit import QuantumCircuit
from qiskit.circuit.library import AND

qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)

qc_and = AND(2)

qc.compose(qc_and, inplace=True)
```
The qiskit.extensions.standard module is deprecated and will be removed in a future release. The gate classes in that module have been moved to qiskit.circuit.library.standard_gates.

Bug Fixes¶

The qiskit.circuit.QuantumCircuit methods inverse(), mirror() methods, as well as the QuantumCircuit.data setter would generate an invalid circuit when used on a parameterized circuit instance. This has been resolved and these methods should now work with a parameterized circuit. Fixes #4235
Previously when creating a controlled version of a standard qiskit gate if a ctrl_state was specified a generic ControlledGate object would be returned whereas without it a standard qiskit controlled gate would be returned if it was defined. This PR allows standard qiskit controlled gates to understand ctrl_state.

Additionally, this PR fixes what might be considered a bug where setting the ctrl_state of an already controlled gate would assume the specified state applied to the full control width instead of the control qubits being added. For instance,:
```
circ = QuantumCircuit(2)
circ.h(0)
circ.x(1)
gate = circ.to_gate()
cgate = gate.control(1)
c3gate = cgate.control(2, ctrl_state=0)
```
would apply ctrl_state to all three control qubits instead of just the two control qubits being added.
Fixed a bug in random_clifford() that stopped it from sampling the full Clifford group. Fixes #4271
The qiskit.circuit.Instruction method qiskit.circuit.Instruction.is_parameterized() method had previously returned True for any Instruction instance which had a qiskit.circuit.Parameter in any element of its params array, even if that Parameter had been fully bound. This has been corrected so that .is_parameterized will return False when the instruction is fully bound.
qiskit.circuit.ParameterExpression.subs() had not correctly detected some cases where substituting parameters would result in a two distinct Parameters objects in an expression with the same name. This has been corrected so a CircuitError will be raised in these cases.
Improve performance of qiskit.quantum_info.Statevector and qiskit.quantum_info.DensityMatrix for low-qubit circuit simulations by optimizing the class __init__ methods. Fixes #4281

The function qiskit.compiler.transpile() now correctly handles when the parameter basis_gates is set to None. This will allow any gate in the output tranpiled circuit, including gates added by the transpilation process. Note that using this parameter may have some unintended consequences during optimization. Some transpiler passes depend on having a basis_gates set. For example, qiskit.transpiler.passes.Optimize1qGates only optimizes the chains of u1, u2, and u3 gates and without basis_gates it is unable to unroll gates that otherwise could be optimized:

from qiskit import *

q = QuantumRegister(1, name='q')
circuit = QuantumCircuit(q)
circuit.h(q[0])
circuit.u1(0.1, q[0])
circuit.u2(0.1, 0.2, q[0])
circuit.h(q[0])
circuit.u3(0.1, 0.2, 0.3, q[0])

result = transpile(circuit, basis_gates=None, optimization_level=3)
result.draw()

     ┌───┐┌─────────────┐┌───┐┌─────────────────┐
q_0: ┤ H ├┤ U2(0.1,0.3) ├┤ H ├┤ U3(0.1,0.2,0.3) ├
     └───┘└─────────────┘└───┘└─────────────────┘

Fixes #3017

Other Notes¶

The objects in qiskit.providers.models which were previously constructed using the marshmallow library have been refactored to not depend on marshmallow. This includes:
- BackendConfiguration
- BackendProperties
- BackendStatus
- QasmBackendConfiguration
- PulseBackendConfiguration
- UchannelLO
- GateConfig
- PulseDefaults
- Command
- JobStatus
- Nduv
- Gate
These should be drop-in replacements without any noticeable change but specifics inherited from marshmallow may not work. Please file issues for any incompatibilities found.

Aer 0.5.1¶

No Change

Ignis 0.3.0¶

No Change

Aqua 0.7.0¶

Prelude¶

The Qiskit Aqua 0.7.0 release introduces a lot of new functionality along with an improved integration with qiskit.circuit.QuantumCircuit objects. The central contributions are the Qiskit’s optimization module, a complete refactor on Operators, using circuits as native input for the algorithms and removal of the declarative JSON API.

Optimization module¶

The qiskit.optimization` module now offers functionality for modeling and solving quadratic programs. It provides various near-term quantum and conventional algorithms, such as the MinimumEigenOptimizer (covering e.g. VQE or QAOA) or CplexOptimizer, as well as a set of converters to translate between different problem representations, such as QuadraticProgramToQubo. See the changelog for a list of the added features.

Operator flow¶

The operator logic provided in qiskit.aqua.operators` was completely refactored and is now a full set of tools for constructing physically-intuitive quantum computations. It contains state functions, operators and measurements and internally relies on Terra’s Operator objects. Computing expectation values and evolutions was heavily simplified and objects like the ExpectationFactory produce the suitable, most efficient expectation algorithm based on the Operator input type. See the changelog for a overview of the added functionality.

Native circuits¶

Algorithms commonly use parameterized circuits as input, for example the VQE, VQC or QSVM. Previously, these inputs had to be of type VariationalForm or FeatureMap which were wrapping the circuit object. Now circuits are natively supported in these algorithms, which means any individually constructed QuantumCircuit can be passed to these algorithms. In combination with the release of the circuit library which offers a wide collection of circuit families, it is now easy to construct elaborate circuits as algorithm input.

Declarative JSON API¶

The ability of running algorithms using dictionaries as parameters as well as using the Aqua interfaces GUI has been removed.

IBM Q Provider 0.7.0¶

New Features¶

A new exception, qiskit.providers.ibmq.IBMQBackendJobLimitError, is now raised if a job could not be submitted because the limit on active jobs has been reached.
qiskit.providers.ibmq.job.IBMQJob and qiskit.providers.ibmq.managed.ManagedJobSet each has two new methods update_name and update_tags. They are used to change the name and tags of a job or a job set, respectively.
qiskit.providers.ibmq.IBMQFactory.save_account() and qiskit.providers.ibmq.IBMQFactory.enable_account() now accept optional parameters hub, group, and project, which allow specifying a default provider to save to disk or use, respectively.

Upgrade Notes¶

The qiskit.providers.ibmq.job.IBMQJob methods creation_date and time_per_step now return date time information as a datetime object in local time instead of UTC. Similarly, the parameters start_datetime and end_datetime, of qiskit.providers.ibmq.IBMQBackendService.jobs() and qiskit.providers.ibmq.IBMQBackend.jobs() can now be specified in local time.
The qiskit.providers.ibmq.job.QueueInfo.format() method now uses a custom datetime to string formatter, and the package arrow is no longer required and has been removed from the requirements list.

Deprecation Notes¶

The from_dict() and to_dict() methods of qiskit.providers.ibmq.job.IBMQJob are deprecated and will be removed in the next release.

Bug Fixes¶

Fixed an issue where nest_asyncio.apply() may raise an exception if there is no asyncio loop due to threading.

Qiskit 0.18.3¶

Terra 0.13.0¶

No Change

Aer 0.5.1¶

Upgrade Notes¶

Changes how transpilation passes are handled in the C++ Controller classes so that each pass must be explicitly called. This allows for greater customization on when each pass should be called, and with what parameters. In particular this enables setting different parameters for the gate fusion optimization pass depending on the QasmController simulation method.
Add gate_length_units kwarg to qiskit.providers.aer.noise.NoiseModel.from_device() for specifying custom gate_lengths in the device noise model function to handle unit conversions for internal code.
Add Controlled-Y (« cy ») gate to the Stabilizer simulator methods supported gateset.
For Aer’s backend the jsonschema validation of input qobj objects from terra is now opt-in instead of being enabled by default. If you want to enable jsonschema validation of qobj set the validate kwarg on the qiskit.providers.aer.QasmSimualtor.run() method for the backend object to True.

Bug Fixes¶

Remove « extended_stabilizer » from the automatically selected simulation methods. This is needed as the extended stabilizer method is not exact and may give incorrect results for certain circuits unless the user knows how to optimize its configuration parameters.

The automatic method now only selects from « stabilizer », « density_matrix », and « statevector » methods. If a non-Clifford circuit that is too large for the statevector method is executed an exception will be raised suggesting you could try explicitly using the « extended_stabilizer » or « matrix_product_state » methods instead.
Fixes Controller classes so that the ReduceBarrier transpilation pass is applied first. This prevents barrier instructions from preventing truncation of unused qubits if the only instruction defined on them was a barrier.
Disables gate fusion for the matrix product state simulation method as this was causing issues with incorrect results being returned in some cases.
Fix error in gate time unit conversion for device noise model with thermal relaxation errors and gate errors. The error probability the depolarizing error was being calculated with gate time in microseconds, while for thermal relaxation it was being calculated in nanoseconds. This resulted in no depolarizing error being applied as the incorrect units would make the device seem to be coherence limited.
Fix bug in incorrect composition of QuantumErrors when the qubits of composed instructions differ.
Fix issue where the « diagonal » gate is checked to be unitary with too high a tolerance. This was causing diagonals generated from Numpy functions to often fail the test.
Fix remove-barrier circuit optimization pass to be applied before qubit trucation. This fixes an issue where barriers inserted by the Terra transpiler across otherwise inactive qubits would prevent them from being truncated.

Ignis 0.3.0¶

No Change

Aqua 0.6.6¶

No Change

IBM Q Provider 0.6.1¶

No Change

Qiskit 0.18.0¶

Terra 0.13.0¶

Prelude¶

The 0.13.0 release includes many big changes. Some highlights for this release are:

For the transpiler we have switched the graph library used to build the qiskit.dagcircuit.DAGCircuit class which is the underlying data structure behind all operations to be based on retworkx for greatly improved performance. Circuit transpilation speed in the 0.13.0 release should be significanlty faster than in previous releases.

There has been a significant simplification to the style in which Pulse instructions are built. Now, Command s are deprecated and a unified set of Instruction s are supported.

The qiskit.quantum_info module includes several new functions for generating random operators (such as Cliffords and quantum channels) and for computing the diamond norm of quantum channels; upgrades to the Statevector and DensityMatrix classes to support computing measurement probabilities and sampling measurements; and several new classes are based on the symplectic representation of Pauli matrices. These new classes include Clifford operators (Clifford), N-qubit matrices that are sparse in the Pauli basis (SparsePauliOp), lists of Pauli’s (PauliTable), and lists of stabilizers (StabilizerTable).

This release also has vastly improved documentation across Qiskit, including improved documentation for the qiskit.circuit, qiskit.pulse and qiskit.quantum_info modules.

Additionally, the naming of gate objects and QuantumCircuit methods have been updated to be more consistent. This has resulted in several classes and methods being deprecated as things move to a more consistent naming scheme.

For full details on all the changes made in this release see the detailed release notes below.

New Features¶

Added a new circuit library module qiskit.circuit.library. This will be a place for constructors of commonly used circuits that can be used as building blocks for larger circuits or applications.
The qiskit.providers.BaseJob class has four new methods:
- done()
- running()
- cancelled()
- in_final_state()
These methods are used to check wheter a job is in a given job status.
Add ability to specify control conditioned on a qubit being in the ground state. The state of the control qubits is represented by an integer. For example:
```
from qiskit import QuantumCircuit
from qiskit.extensions.standard import XGate

qc = QuantumCircuit(4)
cgate = XGate().control(3, ctrl_state=6)
qc.append(cgate, [0, 1, 2, 3])
```
Creates a four qubit gate where the fourth qubit gets flipped if the first qubit is in the ground state and the second and third qubits are in the excited state. If ctrl_state is None, the default, control is conditioned on all control qubits being excited.
A new jupyter widget, %circuit_library_info has been added to qiskit.tools.jupyter. This widget is used for visualizing details about circuits built from the circuit library. For example
from qiskit.circuit.library import XOR import qiskit.tools.jupyter circuit = XOR(5, seed=42) %circuit_library_info circuit
A new kwarg option, formatted , has been added to qiskit.circuit.QuantumCircuit.qasm() . When set to True the method will print a syntax highlighted version (using pygments) to stdout and return None (which differs from the normal behavior of returning the QASM code as a string).
A new kwarg option, filename , has been added to qiskit.circuit.QuantumCircuit.qasm(). When set to a path the method will write the QASM code to that file. It will then continue to output as normal.
A new instruction SetFrequency which allows users to change the frequency of the PulseChannel. This is done in the following way:
```
from qiskit.pulse import Schedule
from qiskit.pulse import SetFrequency

sched = pulse.Schedule()
sched += SetFrequency(5.5e9, DriveChannel(0))
```
In this example, the frequency of all pulses before the SetFrequency command will be the default frequency and all pulses applied to drive channel zero after the SetFrequency command will be at 5.5 GHz. Users of SetFrequency should keep in mind any hardware limitations.
A new method, assign_parameters() has been added to the qiskit.circuit.QuantumCircuit class. This method accepts a parameter dictionary with both floats and Parameters objects in a single dictionary. In other words this new method allows you to bind floats, Parameters or both in a single dictionary.

Also, by using the inplace kwarg it can be specified you can optionally modify the original circuit in place. By default this is set to False and a copy of the original circuit will be returned from the method.
A new method num_nonlocal_gates() has been added to the qiskit.circuit.QuantumCircuit class. This method will return the number of gates in a circuit that involve 2 or or more qubits. These gates are more costly in terms of time and error to implement.
The qiskit.circuit.QuantumCircuit method iso() for adding an Isometry gate to the circuit has a new alias. You can now call qiskit.circuit.QuantumCircuit.isometry() in addition to calling iso.
A description attribute has been added to the CouplingMap class for storing a short description for different coupling maps (e.g. full, grid, line, etc.).

A new method compose() has been added to the DAGCircuit class for composing two circuits via their DAGs.

dag_left.compose(dag_right, edge_map={right_qubit0: self.left_qubit1,
                                  right_qubit1: self.left_qubit4,
                                  right_clbit0: self.left_clbit1,
                                  right_clbit1: self.left_clbit0})

            ┌───┐                    ┌─────┐┌─┐
lqr_1_0: ───┤ H ├───     rqr_0: ──■──┤ Tdg ├┤M├
            ├───┤               ┌─┴─┐└─┬─┬─┘└╥┘
lqr_1_1: ───┤ X ├───     rqr_1: ┤ X ├──┤M├───╫─
         ┌──┴───┴──┐            └───┘  └╥┘   ║
lqr_1_2: ┤ U1(0.1) ├  +  rcr_0: ════════╬════╩═  =
         └─────────┘                    ║
lqr_2_0: ─────■─────     rcr_1: ════════╩══════
            ┌─┴─┐
lqr_2_1: ───┤ X ├───
            └───┘
lcr_0:   ═══════════

lcr_1:   ═══════════

            ┌───┐
lqr_1_0: ───┤ H ├──────────────────
            ├───┤        ┌─────┐┌─┐
lqr_1_1: ───┤ X ├─────■──┤ Tdg ├┤M├
         ┌──┴───┴──┐  │  └─────┘└╥┘
lqr_1_2: ┤ U1(0.1) ├──┼──────────╫─
         └─────────┘  │          ║
lqr_2_0: ─────■───────┼──────────╫─
            ┌─┴─┐   ┌─┴─┐  ┌─┐   ║
lqr_2_1: ───┤ X ├───┤ X ├──┤M├───╫─
            └───┘   └───┘  └╥┘   ║
lcr_0:   ═══════════════════╩════╬═
                                 ║
lcr_1:   ════════════════════════╩═

The mock backends in qiskit.test.mock now have a functional run() method that will return results similar to the real devices. If qiskit-aer is installed a simulation will be run with a noise model built from the device snapshot in the fake backend. Otherwise, qiskit.providers.basicaer.QasmSimulatorPy will be used to run an ideal simulation. Additionally, if a pulse experiment is passed to run and qiskit-aer is installed the PulseSimulator will be used to simulate the pulse schedules.

The qiskit.result.Result() method get_counts() will now return a list of all the counts available when there are multiple circuits in a job. This works when get_counts() is called with no arguments.

The main consideration for this feature was for drawing all the results from multiple circuits in the same histogram. For example it is now possible to do something like:

from qiskit import execute
from qiskit import QuantumCircuit
from qiskit.providers.basicaer import BasicAer
from qiskit.visualization import plot_histogram

sim = BasicAer.get_backend('qasm_simulator')

qc = QuantumCircuit(2)
qc.h(0)
qc.cx(0, 1)
qc.measure_all()
result = execute([qc, qc, qc], sim).result()

plot_histogram(result.get_counts())

A new kwarg, initial_state has been added to the qiskit.visualization.circuit_drawer() function and the QuantumCircuit method draw(). When set to True the initial state will be included in circuit visualizations for all backends. For example:
from qiskit import QuantumCircuit circuit = QuantumCircuit(2) circuit.measure_all() circuit.draw(output='mpl', initial_state=True)

It is now possible to insert a callable into a qiskit.pulse.InstructionScheduleMap which returns a new qiskit.pulse.Schedule when it is called with parameters. For example:

def test_func(x):
   sched = Schedule()
   sched += pulse_lib.constant(int(x), amp_test)(DriveChannel(0))
   return sched

inst_map = InstructionScheduleMap()
inst_map.add('f', (0,), test_func)
output_sched = inst_map.get('f', (0,), 10)
assert output_sched.duration == 10

Two new gate classes, qiskit.extensions.iSwapGate and qiskit.extensions.DCXGate, along with their QuantumCircuit methods iswap() and dcx() have been added to the standard extensions. These gates, which are locally equivalent to each other, can be used to enact particular XY interactions. A brief motivation for these gates can be found in: arxiv.org/abs/quant-ph/0209035
The qiskit.providers.BaseJob class now has a new method wait_for_final_state() that polls for the job status until the job reaches a final state (such as DONE or ERROR). This method also takes an optional callback kwarg which takes a Python callable that will be called during each iteration of the poll loop.
The search_width and search_depth attributes of the qiskit.transpiler.passes.LookaheadSwap pass are now settable when initializing the pass. A larger search space can often lead to more optimized circuits, at the cost of longer run time.
The number of qubits in BackendConfiguration can now be accessed via the property num_qubits. It was previously only accessible via the n_qubits attribute.
Two new methods, angles() and angles_and_phase(), have been added to the qiskit.quantum_info.OneQubitEulerDecomposer class. These methods will return the relevant parameters without validation, and calling the OneQubitEulerDecomposer object will perform the full synthesis with validation.
An RR decomposition basis has been added to the qiskit.quantum_info.OneQubitEulerDecomposer for decomposing an arbitrary 2x2 unitary into a two RGate circuit.
Adds the ability to set qargs to objects which are subclasses of the abstract BaseOperator class. This is done by calling the object op(qargs) (where op is an operator class) and will return a shallow copy of the original object with a qargs property set. When such an object is used with the compose() or dot() methods the internal value for qargs will be used when the qargs method kwarg is not used. This allows for subsystem composition using binary operators, for example:
```
from qiskit.quantum_info import Operator

init = Operator.from_label('III')
x = Operator.from_label('X')
h = Operator.from_label('H')
init @ x([0]) @ h([1])
```
Adds qiskit.quantum_info.Clifford operator class to the quantum_info module. This operator is an efficient symplectic representation an N-qubit unitary operator from the Clifford group. This class includes a to_circuit() method for compilation into a QuantumCircuit of Clifford gates with a minimal number of CX gates for up to 3-qubits. It also providers general compilation for N > 3 qubits but this method is not optimal in the number of two-qubit gates.
Adds qiskit.quantum_info.SparsePauliOp operator class. This is an efficient representaiton of an N-qubit matrix that is sparse in the Pauli basis and uses a qiskit.quantum_info.PauliTable and vector of complex coefficients for its data structure.

This class supports much of the same functionality of the qiskit.quantum_info.Operator class so SparsePauliOp objects can be tensored, composed, scalar multiplied, added and subtracted.

Numpy arrays or Operator objects can be converted to a SparsePauliOp using the :class:`~qiskit.quantum_info.SparsePauliOp.from_operator method. SparsePauliOp can be convered to a sparse csr_matrix or dense Numpy array using the to_matrix method, or to an Operator object using the

Class	Old	New
`QuantumCircuit`	`n_qubits`	`num_qubits`
`Pauli`	`numberofqubits`	`num_qubits`

Function	Old Argument	New Argument
`qiskit.circuit.random.random_circuit()`	`n_qubits`	`num_qubits`
`qiskit.circuit.library.MSGate`	`n_qubits`	`num_qubits`