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ControlledGate

ControlledGate(name, num_qubits, params, label=None, num_ctrl_qubits=1, definition=None, ctrl_state=None, base_gate=None) GitHub(opens in a new tab)

Bases: qiskit.circuit.gate.Gate

Controlled unitary gate.

Create a new ControlledGate. In the new gate the first num_ctrl_qubits of the gate are the controls.

Parameters

  • name (str) – The name of the gate.
  • num_qubits (int) – The number of qubits the gate acts on.
  • params (List) – A list of parameters for the gate.
  • label (Optional[str]) – An optional label for the gate.
  • num_ctrl_qubits (Optional[int]) – Number of control qubits.
  • definition (Optional[QuantumCircuit]) – A list of gate rules for implementing this gate. The elements of the list are tuples of (Gate(), [qubit_list], [clbit_list]).
  • ctrl_state (Union[str, int, None]) – The control state in decimal or as a bitstring (e.g. ‘111’). If specified as a bitstring the length must equal num_ctrl_qubits, MSB on left. If None, use 2**num_ctrl_qubits-1.
  • base_gate (Optional[Gate]) – Gate object to be controlled.

Raises

  • CircuitError – If num_ctrl_qubits >= num_qubits.
  • CircuitError – ctrl_state < 0 or ctrl_state > 2**num_ctrl_qubits.

Examples:

Create a controlled standard gate and apply it to a circuit.

from qiskit import QuantumCircuit, QuantumRegister
from qiskit.circuit.library.standard_gates import HGate
 
qr = QuantumRegister(3)
qc = QuantumCircuit(qr)
c3h_gate = HGate().control(2)
qc.append(c3h_gate, qr)
qc.draw('mpl')

(Source code, png, hires.png, pdf)

../_images/qiskit-circuit-ControlledGate-1.png

Create a controlled custom gate and apply it to a circuit.

from qiskit import QuantumCircuit, QuantumRegister
from qiskit.circuit.library.standard_gates import HGate
 
qc1 = QuantumCircuit(2)
qc1.x(0)
qc1.h(1)
custom = qc1.to_gate().control(2)
 
qc2 = QuantumCircuit(4)
qc2.append(custom, [0, 3, 1, 2])
qc2.draw('mpl')

(Source code, png, hires.png, pdf)

../_images/qiskit-circuit-ControlledGate-2.png

Methods

add_decomposition

ControlledGate.add_decomposition(decomposition)

Add a decomposition of the instruction to the SessionEquivalenceLibrary.

assemble

ControlledGate.assemble()

Assemble a QasmQobjInstruction

broadcast_arguments

ControlledGate.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

ControlledGate.c_if(classical, val)

Set a classical equality condition on this instruction between the register or cbit classical and value val.

Note

This is a setter method, not an additive one. Calling this multiple times will silently override any previously set condition; it does not stack.

control

ControlledGate.control(num_ctrl_qubits=1, label=None, ctrl_state=None)

Return controlled version of gate. See ControlledGate for usage.

Parameters

  • num_ctrl_qubits (int) – number of controls to add to gate (default=1)
  • label (Optional[str]) – optional gate label
  • ctrl_state (Union[str, int, None]) – The control state in decimal or as a bitstring (e.g. ‘111’). If None, use 2**num_ctrl_qubits-1.

Returns

Controlled version of gate. This default algorithm uses num_ctrl_qubits-1 ancillae qubits so returns a gate of size num_qubits + 2*num_ctrl_qubits - 1.

Return type

qiskit.circuit.ControlledGate

Raises

QiskitError – unrecognized mode or invalid ctrl_state

copy

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

inverse

ControlledGate.inverse()

Invert this gate by calling inverse on the base gate.

Return type

ControlledGate

is_parameterized

ControlledGate.is_parameterized()

Return True .IFF. instruction is parameterized else False

power

ControlledGate.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

ControlledGate.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

ControlledGate.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

ControlledGate.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

soft_compare

ControlledGate.soft_compare(other)

Soft comparison between gates. Their names, number of qubits, and classical bit numbers must match. The number of parameters must match. Each parameter is compared. If one is a ParameterExpression then it is not taken into account.

Parameters

other (instruction) – other instruction.

Returns

are self and other equal up to parameter expressions.

Return type

bool

to_matrix

ControlledGate.to_matrix()

Return a Numpy.array for the gate unitary matrix.

Returns

if the Gate subclass has a matrix definition.

Return type

np.ndarray

Raises

CircuitError – If a Gate subclass does not implement this method an exception will be raised when this base class method is called.

validate_parameter

ControlledGate.validate_parameter(parameter)

Gate parameters should be int, float, or ParameterExpression


Attributes

condition_bits

Get Clbits in condition.

Return type

List[Clbit]

ctrl_state

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

Return type

int

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 self.ctrl_state, the returned definition is conjugated with X without changing the internal _definition.

Return type

List

duration

Get the duration.

label

Return instruction label

Return type

str

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.

Return type

str

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.

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