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# qiskit.circuit.library.CXGate¶

class CXGate(label=None, ctrl_state=None)[소스]

Controlled-X gate.

Circuit symbol:

q_0: ──■──
┌─┴─┐
q_1: ┤ X ├
└───┘


Matrix representation:

$\begin{split}CX\ q_0, q_1 = I \otimes |0\rangle\langle0| + X \otimes |1\rangle\langle1| = \begin{pmatrix} 1 & 0 & 0 & 0 \\ 0 & 0 & 0 & 1 \\ 0 & 0 & 1 & 0 \\ 0 & 1 & 0 & 0 \end{pmatrix}\end{split}$

참고

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_1. Thus a textbook matrix for this gate will be:

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

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

In the computational basis, this gate flips the target qubit if the control qubit is in the $$|1\rangle$$ state. In this sense it is similar to a classical XOR gate.

$|a, b\rangle \rightarrow |a, a \oplus b\rangle$

Create new CX gate.

__init__(label=None, ctrl_state=None)[소스]

Create new CX gate.

Methods

 __init__([label, ctrl_state]) Create new CX gate. add_decomposition(decomposition) Add a decomposition of the instruction to the SessionEquivalenceLibrary. 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 controlled-X gate with more control lines. copy([name]) Copy of the instruction. Return inverted CX gate (itself). Return True .IFF. DEPRECATED: use instruction.reverse_ops(). power(exponent) Creates a unitary gate as gate^exponent. Return a default OpenQASM string for the instruction. Creates an instruction with gate repeated n amount of times. For a composite instruction, reverse the order of sub-instructions. Return a numpy.array for the CX gate. 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_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

반환 형식

Instruction

broadcast_arguments(qargs, cargs)

Validation and handling of the arguments and its relationship.

For example, cx([q,q], q) means cx(q, q); cx(q, q). This method yields the arguments in the right grouping. In the given example:

in: [[q,q], q],[]
outs: [q, q], []
[q, q], []


• If len(qargs) == 1:

[q, q] -> [q],[q]

• If len(qargs) == 2:

[[q, q], [r, r]] -> [q, r], [q, r]
[[q], [r, r]]       -> [q, r], [q, r]
[[q, q], [r]]       -> [q, r], [q, r]

• If len(qargs) >= 3:

[q, q], [r, r],  ...] -> [q, r, ...], [q, r, ...]

매개변수
• qargs (List) – List of quantum bit arguments.

• cargs (List) – List of classical bit arguments.

반환 형식

Tuple[List, List]

반환값

A tuple with single arguments.

예외

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)[소스]

Return a controlled-X gate with more control lines.

매개변수
• 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.

반환값

controlled version of this gate.

반환 형식

ControlledGate

copy(name=None)

Copy of the instruction.

매개변수

name (str) – name to be given to the copied circuit, if None then the name stays the same.

반환값

a copy of the current instruction, with the name

updated if it was provided

반환 형식

qiskit.circuit.Instruction

property ctrl_state

Return the control state of the gate as a decimal integer.

반환 형식

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.

반환 형식

List

property duration

Get the duration.

inverse()[소스]

Return inverted CX gate (itself).

is_parameterized()

Return True .IFF. instruction is parameterized else False

property label

Return gate label

반환 형식

str

mirror()

DEPRECATED: use instruction.reverse_ops().

반환값

a new instruction with sub-instructions

reversed.

반환 형식

qiskit.circuit.Instruction

property num_ctrl_qubits

Get number of control qubits.

반환값

The number of control qubits for the gate.

반환 형식

int

property params

Get parameters from base_gate.

반환값

List of gate parameters.

반환 형식

list

예외

CircuitError – Controlled gate does not define a base gate

power(exponent)

Creates a unitary gate as gate^exponent.

매개변수

exponent (float) – Gate^exponent

반환값

To which to_matrix is self.to_matrix^exponent.

반환 형식

qiskit.extensions.UnitaryGate

예외

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 -> c;).

repeat(n)

Creates an instruction with gate repeated n amount of times.

매개변수

n (int) – Number of times to repeat the instruction

반환값

Containing the definition.

반환 형식

qiskit.circuit.Instruction

예외

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.

반환값

a new instruction with

sub-instructions reversed.

반환 형식

qiskit.circuit.Instruction

to_matrix()[소스]

Return a numpy.array for the CX gate.

property unit

Get the time unit of duration.

validate_parameter(parameter)

Gate parameters should be int, float, or ParameterExpression