# Copyright 2019-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License"). You
# may not use this file except in compliance with the License. A copy of
# the License is located at
#
# http://aws.amazon.com/apache2.0/
#
# or in the "license" file accompanying this file. This file is
# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
# ANY KIND, either express or implied. See the License for the specific
# language governing permissions and limitations under the License.
from __future__ import annotations
from typing import Union
QubitInput = Union["Qubit", int]
[docs]class Qubit(int):
"""
A quantum bit index. The index of this qubit is locally scoped towards the contained
circuit. This may not be the exact qubit index on the quantum device.
"""
def __new__(cls, index: int):
"""
Args:
index (int): Index of the qubit.
Raises:
ValueError: If `index` is less than zero.
Examples:
>>> Qubit(0)
>>> Qubit(1)
"""
if index < 0:
raise ValueError(f"Supplied index, {index}, cannot be less than zero.")
return super().__new__(cls, index)
def __repr__(self):
return f"Qubit({super().__repr__()})"
def __str__(self):
return self.__repr__()
[docs] @staticmethod
def new(qubit: QubitInput) -> Qubit:
"""
Helper constructor - if input is a Qubit it returns the same value,
else a new Qubit is constructed.
Args:
qubit (int or Qubit): Qubit index. If type == Qubit then the `qubit` is returned.
"""
if isinstance(qubit, Qubit):
return qubit
else:
return Qubit(qubit)