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MCXVChain

class qiskit.circuit.library.MCXVChain(num_ctrl_qubits=None, dirty_ancillas=False, label=None, ctrl_state=None, *, duration=None, unit='dt', _base_label=None, relative_phase=False, action_only=False)

GitHub

Bases: MCXGate

Implement the multi-controlled X gate using a V-chain of CX gates.

Deprecated since version 1.3_pending

The class qiskit.circuit.library.standard_gates.x.MCXVChain is pending deprecation as of qiskit 1.3. It will be marked deprecated in a future release, and then removed no earlier than 3 months after the release date. It is recommended to use MCXGate and let HighLevelSynthesis choose the best synthesis method depending on the number of ancilla qubits available. If this specific synthesis method is required, one can specify it using the high-level-synthesis plugins n_clean_m15 (using clean ancillas) or n_dirty_i15 (using dirty ancillas) for MCX gates. Alternatively, one can use synth_mcx_n_dirty_i15 and synth_mcx_n_clean_m15 to construct the gate directly.

Parameters

  • dirty_ancillas (bool) – when set to True, the method applies an optimized multicontrolled-X gate up to a relative phase using dirty ancillary qubits with the properties of lemmas 7 and 8 from arXiv:1501.06911, with at most 8*k - 6 CNOT gates. For k within the range {1, …, ceil(n/2)}. And for n representing the total number of qubits.
  • relative_phase (bool) – when set to True, the method applies the optimized multicontrolled-X gate up to a relative phase, in a way that, by lemma 7 of arXiv:1501.06911, the relative phases of the action part cancel out with the phases of the reset part.
  • action_only (bool) – when set to True, the method applies only the action part of lemma 8 from arXiv:1501.06911.
  • num_ctrl_qubits (Optional[int]) –
  • label (Optional[str]) –
  • ctrl_state (Optional[Union[str, int]]) –

Attributes

base_class

Get the base class of this instruction. This is guaranteed to be in the inheritance tree of self.

The “base class” of an instruction is the lowest class in its inheritance tree that the object should be considered entirely compatible with for _all_ circuit applications. This typically means that the subclass is defined purely to offer some sort of programmer convenience over the base class, and the base class is the “true” class for a behavioral perspective. In particular, you should not override base_class if you are defining a custom version of an instruction that will be implemented differently by hardware, such as an alternative measurement strategy, or a version of a parametrized gate with a particular set of parameters for the purposes of distinguishing it in a Target from the full parametrized gate.

This is often exactly equivalent to type(obj), except in the case of singleton instances of standard-library instructions. These singleton instances are special subclasses of their base class, and this property will return that base. For example:

>>> isinstance(XGate(), XGate)
True
>>> type(XGate()) is XGate
False
>>> XGate().base_class is XGate
True

In general, you should not rely on the precise class of an instruction; within a given circuit, it is expected that Instruction.name should be a more suitable discriminator in most situations.

condition

The classical condition on the instruction.

Deprecated since version 1.3.0

The property qiskit.circuit.instruction.Instruction.condition is deprecated as of qiskit 1.3.0. It will be removed in 2.0.0.

condition_bits

Get Clbits in condition.

Deprecated since version 1.3.0

The property qiskit.circuit.instruction.Instruction.condition_bits is deprecated as of qiskit 1.3.0. It will be removed in 2.0.0.

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. If the gate has open controls, as determined from ctrl_state, the returned definition is conjugated with X without changing the internal _definition.

duration

Get the duration.

Deprecated since version 1.3.0

The property qiskit.circuit.instruction.Instruction.duration is deprecated as of qiskit 1.3.0. It will be removed in Qiskit 2.0.0.

label

Return instruction label

mutable

Is this instance is a mutable unique instance or not.

If this attribute is False the gate instance is a shared singleton and is not mutable.

name

Get name of gate. If the gate has open controls the gate name will become:

<original_name_o<ctrl_state>

where <original_name> is the gate name for the default case of closed control qubits and <ctrl_state> is the integer value of the control state for the gate.

num_ancilla_qubits

The number of ancilla qubits.

num_clbits

Return the number of clbits.

num_ctrl_qubits

Get number of control qubits.

Returns

The number of control qubits for the gate.

Return type

int

num_qubits

Return the number of qubits.

params

Get parameters from base_gate.

Returns

List of gate parameters.

Return type

list

Raises

CircuitError – Controlled gate does not define a base gate

unit

Get the time unit of duration.

Deprecated since version 1.3.0

The property qiskit.circuit.instruction.Instruction.unit is deprecated as of qiskit 1.3.0. It will be removed in Qiskit 2.0.0.


Methods

get_num_ancilla_qubits

static get_num_ancilla_qubits(num_ctrl_qubits, mode='v-chain')

GitHub

Get the number of required ancilla qubits.

Parameters

  • num_ctrl_qubits (int) –
  • mode (str) –

inverse

inverse(annotated=False)

GitHub

Invert this gate. The MCX is its own inverse.

Parameters

annotated (bool) – when set to True, this is typically used to return an AnnotatedOperation with an inverse modifier set instead of a concrete Gate. However, for this class this argument is ignored as this gate is self-inverse.

Returns

inverse gate (self-inverse).

Return type

MCXVChain

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