ControlledGate¶

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

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[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           ├
     │  circuit-8 │
q_2: ┤1           ├
     └─────┬──────┘
q_3: ──────■───────

Methods

`add_decomposition`	Add a decomposition of the instruction to the SessionEquivalenceLibrary.
`assemble`	Assemble a QasmQobjInstruction
`broadcast_arguments`	Validation and handling of the arguments and its relationship.
`c_if`	Add classical condition on register or cbit classical and value val.
`control`	Return controlled version of gate.
`copy`	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`	Creates a unitary gate as gate^exponent.
`qasm`	Return a default OpenQASM string for the instruction.
`repeat`	Creates an instruction with gate repeated n amount of times.
`reverse_ops`	For a composite instruction, reverse the order of sub-instructions.
`soft_compare`	Soft comparison between gates.
`to_matrix`	Return a Numpy.array for the gate unitary matrix.
`validate_parameter`	Gate parameters should be int, float, or ParameterExpression

Attributes

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_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

unit¶: Get the time unit of duration.