# Copyright 2018 The Cirq Developers
#
# 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
#
# https://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.
from typing import Any
import numpy as np
from cirq import protocols, linalg
from cirq.testing import lin_alg_utils
[docs]def assert_phase_by_is_consistent_with_unitary(val: Any):
"""Uses `val._unitary_` to check `val._phase_by_`'s behavior."""
original = protocols.unitary(val, None)
if original is None:
# If there's no unitary, it's vacuously consistent.
return
qubit_count = len(original).bit_length() - 1
original = original.reshape((2, 2) * qubit_count)
for t in [0.125, -0.25, 1]:
p = 1j**(t*4)
for i in range(qubit_count):
phased = protocols.phase_by(val, t, i, default=None)
if phased is None:
# If not phaseable, then phase_by is vacuously consistent.
continue
actual = protocols.unitary(phased).reshape((2, 2) * qubit_count)
expected = np.array(original)
s = linalg.slice_for_qubits_equal_to([i], 1)
expected[s] *= p
s = linalg.slice_for_qubits_equal_to([qubit_count + i], 1)
expected[s] *= np.conj(p)
lin_alg_utils.assert_allclose_up_to_global_phase(
actual,
expected,
atol=1e-8,
err_msg='Phased unitary was incorrect for index #{}'.format(i))