qiskit.circuit.library.MCXRecursive¶

class
MCXRecursive
(num_ctrl_qubits=None, label=None, ctrl_state=None)[source]¶ Implement the multicontrolled X gate using recursion.
Using a single ancilla qubit, the multicontrolled X gate is recursively split onto four subregisters. This is done until we reach the 3 or 4controlled X gate since for these we have a concrete implementation that do not require ancillas.
Create new MCX gate.
Methods
__init__
(num_ctrl_qubits[, label, ctrl_state])Create new MCX gate.
add_decomposition
(decomposition)Add a decomposition of the instruction to the SessionEquivalenceLibrary.
assemble
()Assemble a QasmQobjInstruction
broadcast_arguments
(qargs, cargs)Validation and handling of the arguments and its relationship.
c_if
(classical, val)Add classical condition on register classical and value val.
control
([num_ctrl_qubits, label, ctrl_state])Return a multicontrolledX gate with more control lines.
copy
([name])Copy of the instruction.
get_num_ancilla_qubits
(num_ctrl_qubits[, mode])Get the number of required ancilla qubits.
inverse
()Invert this gate.
Return True .IFF.
mirror
()DEPRECATED: use instruction.reverse_ops().
power
(exponent)Creates a unitary gate as gate^exponent.
qasm
()Return a default OpenQASM string for the instruction.
repeat
(n)Creates an instruction with gate repeated n amount of times.
For a composite instruction, reverse the order of subinstructions.
Return a Numpy.array for the gate unitary matrix.
validate_parameter
(parameter)Gate parameters should be int, float, or ParameterExpression
Attributes
Return the control state of the gate as a decimal integer.
Get the decompositions of the instruction from the SessionEquivalenceLibrary.
Return definition in terms of other basic gates.
Get the duration.
Return gate label
The number of ancilla qubits.
Get number of control qubits.
Get parameters from base_gate.
Get the time unit of duration.

add_decomposition
(decomposition)¶ Add a decomposition of the instruction to the SessionEquivalenceLibrary.

assemble
()¶ Assemble a QasmQobjInstruction
 Return type
Instruction

broadcast_arguments
(qargs, cargs)¶ Validation and handling of the arguments and its relationship.
For example,
cx([q[0],q[1]], q[2])
meanscx(q[0], q[2]); cx(q[1], q[2])
. This method yields the arguments in the right grouping. In the given example:in: [[q[0],q[1]], q[2]],[] outs: [q[0], q[2]], [] [q[1], q[2]], []
The general broadcasting rules are:
If len(qargs) == 1:
[q[0], q[1]] > [q[0]],[q[1]]
If len(qargs) == 2:
[[q[0], q[1]], [r[0], r[1]]] > [q[0], r[0]], [q[1], r[1]] [[q[0]], [r[0], r[1]]] > [q[0], r[0]], [q[0], r[1]] [[q[0], q[1]], [r[0]]] > [q[0], r[0]], [q[1], r[0]]
If len(qargs) >= 3:
[q[0], q[1]], [r[0], r[1]], ...] > [q[0], r[0], ...], [q[1], r[1], ...]
 Parameters
qargs (
List
) – List of quantum bit arguments.cargs (
List
) – List of classical bit arguments.
 Return type
Tuple
[List
,List
] Returns
A tuple with single arguments.
 Raises
CircuitError – If the input is not valid. For example, the number of arguments does not match the gate expectation.

c_if
(classical, val)¶ Add classical condition on register classical and value val.

control
(num_ctrl_qubits=1, label=None, ctrl_state=None)¶ Return a multicontrolledX gate with more control lines.
 Parameters
num_ctrl_qubits (int) – number of control qubits.
label (str or None) – An optional label for the gate [Default: None]
ctrl_state (int or str or None) – control state expressed as integer, string (e.g. ‘110’), or None. If None, use all 1s.
 Returns
controlled version of this gate.
 Return type

copy
(name=None)¶ Copy of the instruction.
 Parameters
name (str) – name to be given to the copied circuit, if None then the name stays the same.
 Returns
 a copy of the current instruction, with the name
updated if it was provided
 Return type

property
ctrl_state
¶ Return the control state of the gate as a decimal integer.
 Return type
int

property
decompositions
¶ Get the decompositions of the instruction from the SessionEquivalenceLibrary.

property
definition
¶ Return definition in terms of other basic gates. If the gate has open controls, as determined from self.ctrl_state, the returned definition is conjugated with X without changing the internal _definition.
 Return type
List

property
duration
¶ Get the duration.

static
get_num_ancilla_qubits
(num_ctrl_qubits, mode='recursion')[source]¶ Get the number of required ancilla qubits.

is_parameterized
()¶ Return True .IFF. instruction is parameterized else False

property
label
¶ Return gate label
 Return type
str

mirror
()¶ DEPRECATED: use instruction.reverse_ops().
 Returns
 a new instruction with subinstructions
reversed.
 Return type

property
num_ancilla_qubits
¶ The number of ancilla qubits.

property
num_ctrl_qubits
¶ Get number of control qubits.
 Returns
The number of control qubits for the gate.
 Return type
int

property
params
¶ Get parameters from base_gate.
 Returns
List of gate parameters.
 Return type
list
 Raises
CircuitError – Controlled gate does not define a base gate

power
(exponent)¶ Creates a unitary gate as gate^exponent.
 Parameters
exponent (float) – Gate^exponent
 Returns
To which to_matrix is self.to_matrix^exponent.
 Return type
 Raises
CircuitError – If Gate is not unitary

qasm
()¶ Return a default OpenQASM string for the instruction.
Derived instructions may override this to print in a different format (e.g. measure q[0] > c[0];).

repeat
(n)¶ Creates an instruction with gate repeated n amount of times.
 Parameters
n (int) – Number of times to repeat the instruction
 Returns
Containing the definition.
 Return type
 Raises
CircuitError – If n < 1.

reverse_ops
()¶ For a composite instruction, reverse the order of subinstructions.
This is done by recursively reversing all subinstructions. It does not invert any gate.
 Returns
 a new instruction with
subinstructions reversed.
 Return type

to_matrix
()¶ Return a Numpy.array for the gate unitary matrix.
 Raises
CircuitError – If a Gate subclass does not implement this method an exception will be raised when this base class method is called.
 Return type
ndarray

property
unit
¶ Get the time unit of duration.

validate_parameter
(parameter)¶ Gate parameters should be int, float, or ParameterExpression
