/
barrier.py
48 lines (37 loc) · 1.57 KB
/
barrier.py
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
# 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.
"""Barrier instruction.
Can be applied to a :class:`~qiskit.circuit.QuantumCircuit`
with the :meth:`~qiskit.circuit.QuantumCircuit.barrier` method.
"""
from __future__ import annotations
from qiskit.exceptions import QiskitError
from .instruction import Instruction
class Barrier(Instruction):
"""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.
This will also appear in visualizations as a visual marker.
"""
_directive = True
def __init__(self, num_qubits: int, label: str | None = None):
"""
Args:
num_qubits: the number of qubits for the barrier.
label: the optional label of this barrier.
"""
self._label = label
super().__init__("barrier", num_qubits, 0, [], label=label)
def inverse(self, annotated: bool = False):
"""Special case. Return self."""
return Barrier(self.num_qubits)
def c_if(self, classical, val):
raise QiskitError("Barriers are compiler directives and cannot be conditional.")