qiskit.circuit.library.MCXRecursive¶

class MCXRecursive(num_ctrl_qubits=None, label=None, ctrl_state=None)[source]¶

Implement the multi-controlled X gate using recursion.

Using a single ancilla qubit, the multi-controlled X gate is recursively split onto four sub-registers. This is done until we reach the 3- or 4-controlled X gate since for these we have a concrete implementation that do not require ancillas.

Create new MCX gate.

__init__(num_ctrl_qubits, label=None, ctrl_state=None)[source]¶: 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 multi-controlled-X 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.
`is_parameterized`()	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.
`reverse_ops`()	For a composite instruction, reverse the order of sub-instructions.
`to_matrix`()	Return a Numpy.array for the gate unitary matrix.
`validate_parameter`(parameter)	Gate parameters should be int, float, or ParameterExpression

Attributes

`ctrl_state`	Return the control state of the gate as a decimal integer.
`decompositions`	Get the decompositions of the instruction from the SessionEquivalenceLibrary.
`definition`	Return definition in terms of other basic gates.
`duration`	Get the duration.
`label`	Return gate label
`num_ancilla_qubits`	The number of ancilla qubits.
`num_ctrl_qubits`	Get number of control qubits.
`params`	Get parameters from base_gate.
`unit`	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]) means cx(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 multi-controlled-X 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

ControlledGate

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

qiskit.circuit.Instruction

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.

inverse()[source]¶: Invert this gate. The MCX is its own inverse.

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 sub-instructions: reversed.

Return type

qiskit.circuit.Instruction

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: qiskit.extensions.UnitaryGate
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: qiskit.circuit.Instruction
Raises: CircuitError – If n < 1.

reverse_ops()¶

For a composite instruction, reverse the order of sub-instructions.

This is done by recursively reversing all sub-instructions. It does not invert any gate.

Returns

a new instruction with: sub-instructions reversed.

Return type

qiskit.circuit.Instruction

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