ControlledGate#

class qiskit.circuit.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 (Optional[Union[int, str]]) -- 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)

../_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)

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

Attributes

condition_bits#: Get Clbits in condition.

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. If the gate has open controls, as determined from self.ctrl_state, the returned definition is conjugated with X without changing the internal _definition.

duration#: Get the duration.

label#: Return instruction label

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.

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.

Methods

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.

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.

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.

Return type:

Iterable[tuple[list, list]]

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(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 (str | None) -- optional gate label
ctrl_state (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 ancilla 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(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()[source]#

Invert this gate by calling inverse on the base gate.

Return type:: ControlledGate

is_parameterized()#: Return True .IFF. instruction is parameterized else False

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()#

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];).

Deprecated since version 0.25.0: The method qiskit.circuit.instruction.Instruction.qasm() is deprecated as of qiskit-terra 0.25.0. It will be removed no earlier than 3 months after the release date. Correct exporting to OpenQASM 2 is the responsibility of a larger exporter; it cannot safely be done on an object-by-object basis without context. No replacement will be provided, because the premise is wrong.

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()#

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(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()#

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(parameter)#: Gate parameters should be int, float, or ParameterExpression