Source code for qiskit.circuit.barrier
# This code is part of Qiskit.
# (C) Copyright IBM 2017.
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at http://www.apache.org/licenses/LICENSE-2.0.
# Any modifications or derivative works of this code must retain this
# copyright notice, and modified files need to carry a notice indicating
# that they have been altered from the originals.
Can be applied to a :class:`~qiskit.circuit.QuantumCircuit`
with the :meth:`~qiskit.circuit.QuantumCircuit.barrier` method.
from qiskit.exceptions import QiskitError
from .instruction import Instruction
A barrier is a visual indicator of the grouping of a circuit section.
It also acts as a directive for circuit compilation to separate pieces
of a circuit so that any optimizations or re-writes are constrained
to only act between barriers."""
_directive = True
def __init__(self, num_qubits, label=None):
"""Create new barrier instruction.
num_qubits (int): the number of qubits for the barrier type [Default: 0].
label (str): the barrier label
TypeError: if barrier label is invalid.
self._label = label
super().__init__("barrier", num_qubits, 0, , label=label)
[docs] def inverse(self):
"""Special case. Return self."""
[docs] def broadcast_arguments(self, qargs, cargs):
yield [qarg for sublist in qargs for qarg in sublist], 
[docs] def c_if(self, classical, val):
raise QiskitError("Barriers are compiler directives and cannot be conditional.")