# -*- coding: utf-8 -*-
# Copyright 2021 Huawei Technologies Co., Ltd
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License 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.
# ============================================================================
"""Bitphaseflip operator."""
from mindquantum.core.gates import Z
from mindquantum.core.circuit import Circuit
from mindquantum.utils.type_value_check import _check_input_type
[docs]def bitphaseflip_operator(phase_inversion_index, n_qubits):
"""
This operator generate a circuit that can flip the sign of any calculation bases.
Args:
phase_inversion_index (list[int]): Index of calculation bases want to flip phase.
n_qubits (int): Total number of qubits.
Examples:
>>> from mindquantum.core.circuit import Circuit
>>> from mindquantum import UN, H, Z
>>> from mindquantum.algorithm.library import bitphaseflip_operator
>>> circuit = Circuit()
>>> circuit += UN(H, 3)
>>> circuit += bitphaseflip_operator([1, 3], 3)
>>> print(circuit.get_qs(ket=True))
√2/4¦000⟩
-√2/4¦001⟩
√2/4¦010⟩
-√2/4¦011⟩
√2/4¦100⟩
√2/4¦101⟩
√2/4¦110⟩
√2/4¦111⟩
Returns:
Circuit, the bit phase flip circuit.
"""
_check_input_type('n_qubits', int, n_qubits)
_check_input_type('phase_inversion_index', (list, range), phase_inversion_index)
s = [1 for i in range(1 << n_qubits)]
for i in phase_inversion_index:
s[i] = -1
if s[0] == -1:
for i in range(len(s)):
s[i] = -1 * s[i]
circuit = Circuit()
length = len(s)
cz = []
for i in range(length):
if s[i] == -1:
cz.append([])
current = i
t = 0
while current != 0:
if (current & 1) == 1:
cz[-1].append(t)
t += 1
current = current >> 1
for j in range(i + 1, length):
if i & j == i:
s[j] = -1 * s[j]
for i in cz:
if i:
if len(i) > 1:
circuit += Z.on(i[-1], i[:-1])
else:
circuit += Z.on(i[0])
return circuit