CCXGate

class qiskit.circuit.library.CCXGate(*args, _force_mutable=False, **kwargs)

Bases: SingletonControlledGate

CCX gate, also known as Toffoli gate.

Can be applied to a QuantumCircuit with the ccx() and toffoli() methods.

Circuit symbol:

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

Matrix representation:

CCX q_0, q_1, q_2 = I \otimes I \otimes |0 \rangle \langle 0| + CX \otimes |1 \rangle \langle 1| = \begin{pmatrix} 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0\\ 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0\\ 0 & 0 & 1 & 0 & 0 & 0 & 0 & 0\\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1\\ 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0\\ 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0\\ 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0\\ 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0 \end{pmatrix}

Note

In Qiskit’s convention, higher qubit indices are more significant (little endian convention). In many textbooks, controlled gates are presented with the assumption of more significant qubits as control, which in our case would be q_2 and q_1. Thus a textbook matrix for this gate will be:

     ┌───┐
q_0: ┤ X ├
     └─┬─┘
q_1: ──■──
       │
q_2: ──■──

CCX\ q_2, q_1, q_0 = |0 \rangle \langle 0| \otimes I \otimes I + |1 \rangle \langle 1| \otimes CX = \begin{pmatrix} 1 & 0 & 0 & 0 & 0 & 0 & 0 & 0\\ 0 & 1 & 0 & 0 & 0 & 0 & 0 & 0\\ 0 & 0 & 1 & 0 & 0 & 0 & 0 & 0\\ 0 & 0 & 0 & 1 & 0 & 0 & 0 & 0\\ 0 & 0 & 0 & 0 & 1 & 0 & 0 & 0\\ 0 & 0 & 0 & 0 & 0 & 1 & 0 & 0\\ 0 & 0 & 0 & 0 & 0 & 0 & 0 & 1\\ 0 & 0 & 0 & 0 & 0 & 0 & 1 & 0 \end{pmatrix}

Create new CCX gate.

Attributes

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.

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.

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.

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

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.

Return instruction label

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.

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.

Return the number of clbits.

Get number of control qubits.

Returns

The number of control qubits for the gate.

Return type

int

Return the number of qubits.

Get parameters from base_gate.

Returns

List of gate parameters.

Return type

list

Raises

CircuitError - Controlled gate does not define a base gate

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.

control(num_ctrl_qubits=1, label=None, ctrl_state=None, annotated=False)

Controlled version of this gate.

Parameters

num_ctrl_qubits (int) – number of control qubits.
label (str | None) – An optional label for the gate [Default: None]
ctrl_state (int |str | None) – control state expressed as integer, string (e.g. '110'), or None. If None, use all 1s.
annotated (bool) – indicates whether the controlled gate should be implemented as an annotated gate.

Returns

controlled version of this gate.

Return type

ControlledGate

inverse(annotated=False)

Return an inverted CCX gate (also a CCX).

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

CCXGate

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