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qiskit.circuit.ControlledGate

class ControlledGate(name, num_qubits, params, label=None, num_ctrl_qubits=1, definition=None, ctrl_state=None, base_gate=None)

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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[int, str, 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()
           
q0_0: ──■──

q0_1: ──■──
      ┌─┴─┐
q0_2: ┤ H ├
      └───┘

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()
                   
q_0: ──────■───────
     ┌─────┴──────┐
q_1:0
     │  circuit14 │
q_2:1
     └─────┬──────┘
q_3: ──────■───────
                   

__init__

__init__(name, num_qubits, params, label=None, num_ctrl_qubits=1, definition=None, ctrl_state=None, base_gate=None)

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[int, str, 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()
           
q1_0: ──■──

q1_1: ──■──
      ┌─┴─┐
q1_2: ┤ H ├
      └───┘

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()
                   
q_0: ──────■───────
     ┌─────┴──────┐
q_1:0
     │  circuit31 │
q_2:1
     └─────┬──────┘
q_3: ──────■───────
                   

Methods

__init__(name, num_qubits, params[, label, …])Create a new ControlledGate.
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 controlled version of gate.
copy([name])Copy of the instruction.
inverse()Invert this gate by calling inverse on the base 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_stateReturn the control state of the gate as a decimal integer.
decompositionsGet the decompositions of the instruction from the SessionEquivalenceLibrary.
definitionReturn definition in terms of other basic gates.
durationGet the duration.
labelReturn gate label
num_ctrl_qubitsGet number of control qubits.
paramsGet parameters from base_gate.
unitGet the time unit of duration.

add_decomposition

add_decomposition(decomposition)

Add a decomposition of the instruction to the SessionEquivalenceLibrary.

assemble

assemble()

Assemble a QasmQobjInstruction

Return type

Instruction

broadcast_arguments

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

c_if(classical, val)

Add classical condition on register classical and value val.

control

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

Return controlled version of gate. See ControlledGate for usage.

Parameters

  • num_ctrl_qubits (Optional[int]) – number of controls to add to gate (default=1)
  • label (Optional[str]) – optional gate label
  • ctrl_state (Union[int, str, 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

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

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.

inverse

inverse()

Invert this gate by calling inverse on the base gate.

Return type

ControlledGate

is_parameterized

is_parameterized()

Return True .IFF. instruction is parameterized else False

label

Return gate label

Return type

str

mirror

mirror()

DEPRECATED: use instruction.reverse_ops().

Returns

a new instruction with sub-instructions

reversed.

Return type

qiskit.circuit.Instruction

num_ctrl_qubits

Get number of control qubits.

Returns

The number of control qubits for the gate.

Return type

int

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

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

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

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

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

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

unit

Get the time unit of duration.

validate_parameter

validate_parameter(parameter)

Gate parameters should be int, float, or ParameterExpression

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