Target

class qiskit.transpiler.Target(description=None, num_qubits=0, dt=None, granularity=1, min_length=1, pulse_alignment=1, acquire_alignment=1, qubit_properties=None, concurrent_measurements=None, **_subclass_kwargs)

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Bases: BaseTarget

The intent of the Target object is to inform Qiskit’s compiler about the constraints of a particular backend so the compiler can compile an input circuit to something that works and is optimized for a device. It currently contains a description of instructions on a backend and their properties as well as some timing information. However, this exact interface may evolve over time as the needs of the compiler change. These changes will be done in a backwards compatible and controlled manner when they are made (either through versioning, subclassing, or mixins) to add on to the set of information exposed by a target.

As a basic example, let’s assume backend has two qubits, supports UGate on both qubits and CXGate in both directions. To model this you would create the target like:

from qiskit.transpiler import Target, InstructionProperties
from qiskit.circuit.library import UGate, CXGate
from qiskit.circuit import Parameter
 
gmap = Target()
theta = Parameter('theta')
phi = Parameter('phi')
lam = Parameter('lambda')
u_props = {
    (0,): InstructionProperties(duration=5.23e-8, error=0.00038115),
    (1,): InstructionProperties(duration=4.52e-8, error=0.00032115),
}
gmap.add_instruction(UGate(theta, phi, lam), u_props)
cx_props = {
    (0,1): InstructionProperties(duration=5.23e-7, error=0.00098115),
    (1,0): InstructionProperties(duration=4.52e-7, error=0.00132115),
}
gmap.add_instruction(CXGate(), cx_props)

Each instruction in the Target is indexed by a unique string name that uniquely identifies that instance of an Instruction object in the Target. There is a 1:1 mapping between a name and an Instruction instance in the target and each name must be unique. By default, the name is the name attribute of the instruction, but can be set to anything. This lets a single target have multiple instances of the same instruction class with different parameters. For example, if a backend target has two instances of an RXGate one is parameterized over any theta while the other is tuned up for a theta of pi/6 you can add these by doing something like:

import math
 
from qiskit.transpiler import Target, InstructionProperties
from qiskit.circuit.library import RXGate
from qiskit.circuit import Parameter
 
target = Target()
theta = Parameter('theta')
rx_props = {
    (0,): InstructionProperties(duration=5.23e-8, error=0.00038115),
}
target.add_instruction(RXGate(theta), rx_props)
rx_30_props = {
    (0,): InstructionProperties(duration=1.74e-6, error=.00012)
}
target.add_instruction(RXGate(math.pi / 6), rx_30_props, name='rx_30')

Then in the target object accessing by rx_30 will get the fixed angle RXGate while rx will get the parameterized RXGate.

You can optionally specify a bound on valid values on a gate in the target by using the angle_bounds keyword argument when calling the add_instruction() method. Bounds are set on operations not individual instructions, so when you call add_instruction() the bounds are applied for all qargs that it is defined on. The bounds are specified of a list of 2-tuples of floats where the first float is the lower bound and the second float is the upper bound. For example, if you specfied an angle bound:

[(0.0, 3.14), (-3.14, 3.14), (0.0, 1.0)]

this indicates the angle bounds for a 3 parameter gate where the first parameter accepts angles between 0 and 3.14, the second between -3.14 and 3.14, and the third parameter between 0 and 1. All bounds are set inclusively as well. A bound can also be specified with None instead of a 2-tuple which indicates that parameter has no constraints. For example:

[(0.0, 3.14, None, None)]

indicates an angle bound for a 3 parameter gate where only the first parameter is restricted to angles between 0.0 and 3.14 and the other parameters accept any value.

You can check if any operations in the target have angle bounds set with, has_angle_bounds() and also if a specific name in the target has angle bounds set with gate_has_angle_bounds(). Whether a particular set of parameter values conforms to the angle bounds can be checked with supported_angle_bound(). In the preset pass managers the WrapAngles pass is used to enforce the angle bounds, for this to work you need to provide a function to the WrapAngleRegistry used by the pass. You can see more details on this in: Angle bounds on Gates.

This class can be queried via the mapping protocol, using the instruction’s name as a key. You can modify any property for an instruction via the update_instruction_properties() method. Modification via the mapping protocol or mutating the attributes of a InstructionProperties object is not supported and doing so will invalidate the internal state of the object.

Note

This class assumes that qubit indices start at 0 and are a contiguous set if you want a submapping the bits will need to be reindexed in a new Target object.

Note

This class only supports additions of gates, qargs, and properties. If you need to remove one of these the best option is to iterate over an existing object and create a new subset (or use one of the methods to do this). The object internally caches different views and these would potentially be invalidated by removals.

Subclassing

While it is technically possible to subclass Target, beware that the majority of the built-in information is in Rust and is queried from Rust in built-in transpiler passes. Python-space overrides are not visible to Rust, and you should not rely on these to change the behavior of Qiskit’s built-in transpiler passes. Target is largely supposed to be a representation of a QPU that has specialized constructors, not specialized subclasses; the usual API for constructing a Target should be a function that returns a base Target, not a subclass with a custom initializer.

You may use subclassing to add addition Python-space properties to your Target, for example to then interpret in custom backend-specific transpiler stages; the Target is passed to stage-plugin constructors.

You should not subclass Target to attempt to modify the behavior of Qiskit’s built-in passes; the Python-space subclassing will not be seen by passes written in Rust.

Further, as the core of Target is written in Rust, it uses __new__() as its initializer, and you must ensure that the correct arguments are passed through to the underlying implementation. If you override the signature of the __init__() method, you must also include an override of __new__() with the same signature, which calls super().__new__() in a correct manner.

Create a new Target object.

param description

An optional string to describe the Target.

type description

str

param num_qubits

An optional int to specify the number of qubits the backend target has. This is not a hard limit on the construction; any call to add_instruction() will cause the set num_qubits to update to accommodate any concrete qargs in the given properties.

This can be explicitly set to None to indicate a Target representing a simulator or other abstract machine that imposes no limits on the number of qubits. In this case, all instructions added to the target should be global (with properties=None or properties={None: None}).

type num_qubits

int

param dt

The system time resolution of input signals in seconds

type dt

float

param granularity

An integer value representing minimum pulse gate resolution in units of dt. A user-defined pulse gate should have duration of a multiple of this granularity value.

type granularity

int

param min_length

An integer value representing minimum pulse gate length in units of dt. A user-defined pulse gate should be longer than this length.

type min_length

int

param pulse_alignment

An integer value representing a time resolution of gate instruction starting time. Gate instruction should start at time which is a multiple of the alignment value.

type pulse_alignment

int

param acquire_alignment

An integer value representing a time resolution of measure instruction starting time. Measure instruction should start at time which is a multiple of the alignment value.

type acquire_alignment

int

param qubit_properties

A list of QubitProperties objects defining the characteristics of each qubit on the target device. If specified the length of this list must match the number of qubits in the target, where the index in the list matches the qubit number the properties are defined for. If some qubits don’t have properties available you can set that entry to None

type qubit_properties

list

param concurrent_measurements

A list of sets of qubits that must be measured together. This must be provided as a nested list like [[0, 1], [2, 3, 4]].

type concurrent_measurements

list

raises ValueError

If both num_qubits and qubit_properties are both defined and the value of num_qubits differs from the length of qubit_properties.

Attributes

acquire_alignment

concurrent_measurements

description

dt

Return dt.

granularity

instructions

Get the list of tuples (Instruction, (qargs)) for the target

For globally defined variable width operations the tuple will be of the form (class, None) where class is the actual operation class that is globally defined.

min_length

num_qubits

operation_names

Get the operation names in the target.

operations

Get the operation objects in the target.

physical_qubits

Returns a sorted list of physical qubits.

pulse_alignment

qargs

The set of qargs in the target.

qubit_properties

Methods

add_instruction

add_instruction(instruction, properties=None, name=None, *, angle_bounds=None)

GitHub

Add a new instruction to the Target

As Target objects are strictly additive this is the primary method for modifying a Target. Typically, you will use this to fully populate a Target before using it in BackendV2. For example:

from qiskit.circuit.library import CXGate
from qiskit.transpiler import Target, InstructionProperties
 
target = Target()
cx_properties = {
    (0, 1): None,
    (1, 0): None,
    (0, 2): None,
    (2, 0): None,
    (0, 3): None,
    (2, 3): None,
    (3, 0): None,
    (3, 2): None
}
target.add_instruction(CXGate(), cx_properties)

Will add a CXGate to the target with no properties (duration, error, etc) with the coupling edge list: (0, 1), (1, 0), (0, 2), (2, 0), (0, 3), (2, 3), (3, 0), (3, 2). If there are properties available for the instruction you can replace the None value in the properties dictionary with an InstructionProperties object. This pattern is repeated for each Instruction the target supports.

Parameters

instruction (Union[qiskit.circuit.Instruction, Type[qiskit.circuit.Instruction]]) – The operation object to add to the map. If it’s parameterized any value of the parameter can be set. Optionally for variable width instructions (such as control flow operations such as ForLoop or MCXGate) you can specify the class. If the class is specified than the name argument must be specified. When a class is used the gate is treated as global and not having any properties set.
properties (dict) – A dictionary of qarg entries to an InstructionProperties object for that instruction implementation on the backend. Properties are optional for any instruction implementation, if there are no InstructionProperties available for the backend the value can be None. If there are no constraints on the instruction (as in a noiseless/ideal simulation) this can be set to {None, None} which will indicate it runs on all qubits (or all available permutations of qubits for multi-qubit gates). The first None indicates it applies to all qubits and the second None indicates there are no InstructionProperties for the instruction. By default, if properties is not set it is equivalent to passing {None: None}.
name (str) – An optional name to use for identifying the instruction. If not specified the name attribute of gate will be used. All gates in the Target need unique names. Backends can differentiate between different parameterization of a single gate by providing a unique name for each (e.g. “rx30”, “rx60”, `”rx90”`` similar to the example in the documentation for the Target class).
angle_bounds (list) – The bounds on the parameters for a given gate. This is specified by a list of tuples (low, high) which represent the low and high bound (inclusively) on what float values are allowed for the parameter in that position. If a parameter doesn’t have an angle bound you can use None to represent that. For example if a 3 parameter gate only had a bound on the second parameter you would represent that with: [None, [0, 3.14], None] which means the first and third parameter allow any value but the second parameter only accepts values between 0 and 3.14.

Raises

AttributeError – If gate is already in map
TranspilerError – If an operation class is passed in for instruction and no name is specified or properties is set.

build_coupling_map

build_coupling_map(two_q_gate=None, filter_idle_qubits=False)

GitHub

Get a CouplingMap from this target.

If there is a mix of two qubit operations that have a connectivity constraint and those that are globally defined this will also return None because the globally connectivity means there is no constraint on the target. If you wish to see the constraints of the two qubit operations that have constraints you should use the two_q_gate argument to limit the output to the gates which have a constraint.

Parameters

two_q_gate (str) – An optional gate name for a two qubit gate in the Target to generate the coupling map for. If specified the output coupling map will only have edges between qubits where this gate is present.
filter_idle_qubits (bool) – If set to True the output CouplingMap will remove any qubits that don’t have any operations defined in the target. Note that using this argument will result in an output CouplingMap object which has holes in its indices which might differ from the assumptions of the class. The typical use case of this argument is to be paired with CouplingMap.connected_components() which will handle the holes as expected.

Returns

The CouplingMap object

for this target. If there are no connectivity constraints in the target this will return None.

Return type

CouplingMap

Raises

ValueError – If a non-two qubit gate is passed in for two_q_gate.
IndexError – If an Instruction not in the Target is passed in for two_q_gate.

durations

durations()

GitHub

Get an InstructionDurations object from the target

Returns

The instruction duration represented in the

target

Return type

InstructionDurations

from_configuration

classmethod from_configuration(basis_gates, num_qubits=None, coupling_map=None, instruction_durations=None, concurrent_measurements=None, dt=None, timing_constraints=None, custom_name_mapping=None)

GitHub

Create a target object from the individual global configuration

Prior to the creation of the Target class, the constraints of a backend were represented by a collection of different objects which combined represent a subset of the information contained in the Target. This function provides a simple interface to convert those separate objects to a Target.

This constructor will use the input from basis_gates, num_qubits, and coupling_map to build a base model of the backend and the instruction_durations, backend_properties, and inst_map inputs are then queried (in that order) based on that model to look up the properties of each instruction and qubit. If there is an inconsistency between the inputs any extra or conflicting information present in instruction_durations, backend_properties, or inst_map will be ignored.

Parameters

basis_gates (list[str]) – The list of basis gate names for the backend. For the target to be created these names must either be in the output from get_standard_gate_name_mapping() or present in the specified custom_name_mapping argument.
num_qubits (int | None) – The number of qubits supported on the backend.
coupling_map (CouplingMap | None) – The coupling map representing connectivity constraints on the backend. If specified all gates from basis_gates will be supported on all qubits (or pairs of qubits).
instruction_durations (InstructionDurations | None) – Optional instruction durations for instructions. If specified it will take priority for setting the duration field in the InstructionProperties objects for the instructions in the target.
concurrent_measurements (list) – A list of sets of qubits that must be measured together. This must be provided as a nested list like [[0, 1], [2, 3, 4]].
dt (float | None) – The system time resolution of input signals in seconds
timing_constraints (TimingConstraints | None) – Optional timing constraints to include in the Target
custom_name_mapping (dict[str, Any] | None) – An optional dictionary that maps custom gate/operation names in basis_gates to an Operation object representing that gate/operation. By default, most standard gates names are mapped to the standard gate object from qiskit.circuit.library this only needs to be specified if the input basis_gates defines gates in names outside that set.

Returns

the target built from the input configuration

Return type

Target

Raises

TranspilerError – If the input basis gates contain > 2 qubits and coupling_map is
specified. –
KeyError – If no mapping is available for a specified basis_gate.

gate_has_angle_bounds

gate_has_angle_bounds(name)

Check if a specific gate gate has an angle bound set

Parameters

name (str) – The instruction name to check if it has an angle bound set

Returns

This will return True if the gate is in the target and has angle bounds defined. It will return False if the gate does not have angle bounds defined or is not in the target.

Return type

bool

get

get(key, default=None)

GitHub

Gets an item from the Target. If not found return a provided default or None.

get_non_global_operation_names

get_non_global_operation_names(strict_direction=False)

GitHub

Return the non-global operation names for the target

The non-global operations are those in the target which don’t apply on all qubits (for single qubit operations) or all multi-qubit qargs (for multi-qubit operations).

Parameters

strict_direction (bool) – If set to True the multi-qubit operations considered as non-global respect the strict direction (or order of qubits in the qargs is significant). For example, if cx is defined on (0, 1) and ecr is defined over (1, 0) by default neither would be considered non-global, but if strict_direction is set True both cx and ecr would be returned.

Returns

A list of operation names for operations that aren’t global in this target

Return type

List[str]

has_angle_bounds

has_angle_bounds()

Check if there are any angle bounds set in the target

Returns

This will return True if there are angle bounds set on any instructions in the circuit

Return type

bool

instruction_properties

instruction_properties(index)

GitHub

Get the instruction properties for a specific instruction tuple

This method is to be used in conjunction with the instructions attribute of a Target object. You can use this method to quickly get the instruction properties for an element of instructions by using the index in that list. However, if you’re not working with instructions directly it is likely more efficient to access the target directly via the name and qubits to get the instruction properties. For example, if instructions returned:

[(XGate(), (0,)), (XGate(), (1,))]

you could get the properties of the XGate on qubit 1 with:

props = target.instruction_properties(1)

but just accessing it directly via the name would be more efficient:

props = target['x'][(1,)]

(assuming the XGate’s canonical name in the target is 'x') This is especially true for larger targets as this will scale worse with the number of instruction tuples in a target.

Parameters

index (int) – The index of the instruction tuple from the instructions attribute. For, example if you want the properties from the third element in instructions you would set this to be 2.

Returns

The instruction properties for the specified instruction tuple

Return type

InstructionProperties

instruction_supported

instruction_supported(operation_name=None, qargs=Ellipsis, operation_class=None, parameters=None, check_angle_bounds=True)

Return whether the instruction (operation + qubits) is supported by the target

Parameters

operation_name (str) – The name of the operation for the instruction. Either this or operation_class must be specified, if both are specified operation_class will take priority and this argument will be ignored.
qargs (tuple) – The tuple of qubit indices for the instruction. If this is not specified then this method will return True if the specified operation is supported on any qubits. The typical application will always have this set (otherwise it’s the same as just checking if the target contains the operation). Normally you would not set this argument if you wanted to check more generally that the target supports an operation with the parameters on any qubits.
operation_class (Type[qiskit.circuit.Instruction]) – The operation class to check whether the target supports a particular operation by class rather than by name. This lookup is more expensive as it needs to iterate over all operations in the target instead of just a single lookup. If this is specified it will supersede the operation_name argument. The typical use case for this operation is to check whether a specific variant of an operation is supported on the backend. For example, if you wanted to check whether a RXGate was supported on a specific qubit with a fixed angle. That fixed angle variant will typically have a name different from the object’s name attribute ("rx") in the target. This can be used to check if any instances of the class are available in such a case.
parameters (list) –

A list of parameters to check if the target supports them on the specified qubits. If the instruction supports the parameter values specified in the list on the operation and qargs specified this will return True but if the parameters are not supported on the specified instruction it will return False. If this argument is not specified this method will return True if the instruction is supported independent of the instruction parameters. If specified with any Parameter objects in the list, that entry will be treated as supporting any value, however parameter names will not be checked (for example if an operation in the target is listed as parameterized with "theta" and "phi" is passed into this function that will return True). For example, if called with:
```
parameters = [Parameter("theta")]
target.instruction_supported("rx", (0,), parameters=parameters)
```
will return True if an RXGate is supported on qubit 0 that will accept any parameter. If you need to check for a fixed numeric value parameter this argument is typically paired with the operation_class argument. For example:
```
target.instruction_supported("rx", (0,), RXGate, parameters=[pi / 4])
```
will return True if an RXGate(pi/4) exists on qubit 0.
check_angle_bounds (bool) – If set to True (the default) the value of parameters will be validated against any angle bounds set in the target. If any of the values in parameters are set to be ParameterExpression instances this flag will have no effect as angle bounds only impact non-parameterized operations in the circuit.

Returns

Returns True if the instruction is supported and False if it isn’t.

Return type

bool

items

items()

GitHub

Returns pairs of Gate names and its property map (str, dict[tuple, InstructionProperties])

keys

keys()

GitHub

Return the keys (operation_names) of the Target

operation_from_name

operation_from_name(instruction)

Get the operation class object for a given name

Parameters

instruction (str) – The instruction name to get the Instruction instance for

Returns

The Instruction instance corresponding to the name. This also can also be the class for globally defined variable with operations.

Return type

qiskit.circuit.Instruction

operation_names_for_qargs

operation_names_for_qargs(qargs, /)

Get the operation names for a specified qargs tuple

Parameters

qargs (tuple) – A qargs tuple of the qubits to get the gates that apply to it. For example, (0,) will return the set of all instructions that apply to qubit 0. If set to None this will return the names for any globally defined operations in the target.

Returns

The set of operation names that apply to the specified qargs.

Return type

set

Raises

KeyError – If qargs is not in target

operations_for_qargs

operations_for_qargs(qargs, /)

Get the operation class object for a specified qargs tuple

Parameters

qargs (tuple) – A qargs tuple of the qubits to get the gates that apply to it. For example, (0,) will return the set of all instructions that apply to qubit 0. If set to None this will return any globally defined operations in the target.

Returns

The list of Instruction instances that apply to the specified qarg. This may also be a class if a variable width operation is globally defined.

Return type

list

Raises

KeyError – If qargs is not in target

qargs_for_operation_name

qargs_for_operation_name(operation)

GitHub

Get the qargs for a given operation name

Parameters

operation (str) – The operation name to get qargs for

Returns

The set of qargs the gate instance applies to.

Return type

set

seconds_to_dt

seconds_to_dt(duration)

GitHub

Convert a given duration in seconds to units of dt

Parameters

duration (float) – The duration in seconds, such as in an InstructionProperties field for an instruction in the target.

Return type

int

Returns

duration: The duration in units of dt

supported_angle_bound

supported_angle_bound(name, angles)

Check that parameters on a specific gate conform to the angle bounds

Parameters

name (str) – The instruction name to check the angle bounds of
angles (list) – A list of float parameter values for name to see if they conform to the defined angle bounds.

Returns

Returns True if the parameter values specified are compatible with the angle bounds. False is returned if the any of the parameters are outside the defined bounds.

Return type

bool

Raises

TranspilerError – If name is not in the target or does not
have angle bounds defined. –

timing_constraints

timing_constraints()

GitHub

Get an TimingConstraints object from the target

Returns

The timing constraints represented in the Target

Return type

TimingConstraints

update_instruction_properties

update_instruction_properties(instruction, qargs, properties)

GitHub

Update the property object for an instruction qarg pair already in the Target.

For ease of access, a user is able to obtain the mapping between an instruction’s applicable qargs and its instruction properties via the mapping protocol (using __getitem__), with the instruction’s name as the key. This method is the only way to modify/update the properties of an instruction in the Target. Usage of the mapping protocol for modifications is not supported.

Parameters

instruction (str) – The instruction name to update
qargs (tuple) – The qargs to update the properties of
properties (InstructionProperties) – The properties to set for this instruction

Raises

KeyError – If instruction or qarg are not in the target

values

values()

GitHub

Return the Property Map (qargs -> InstructionProperties) of every instruction in the Target

Parameters

description (str | None) –
num_qubits (int | None) –
dt (float | None) –
granularity (int) –
min_length (int) –
pulse_alignment (int) –
acquire_alignment (int) –
qubit_properties (list | None) –
concurrent_measurements (list | None) –

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