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
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"""Barrier instruction.

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

[docs]class Barrier(Instruction): """Barrier 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. Args: num_qubits (int): the number of qubits for the barrier type [Default: 0]. label (str): the barrier label Raises: 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.""" return Barrier(self.num_qubits)
[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.")