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ControlledGate

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

Bases: 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-93 │
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

Set a classical equality condition on this instruction between the 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.

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

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.