Source code for pennylane.measurements.null_measurement
# Copyright 2018-2025 Xanadu Quantum Technologies Inc.
# 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.
"""
This module contains the qml.mutual_info measurement.
"""
import numpy as np
from .measurements import SampleMeasurement, StateMeasurement
[docs]
class NullMeasurement(SampleMeasurement, StateMeasurement):
"""A measurement that strictly returns an array with one nan.
This measurement is for profiling problems without the overhead of performing a measurement.
>>> @qml.qnode(qml.device('default.qubit', wires=1), diff_method="parameter-shift")
... def circuit():
... return qml.measurements.NullMeasurement()
...
>>> circuit()
array(nan)
``np.array(np.nan)`` is chosen so the result still has a shape and data type for integration
with jax, catalyst, and program capture.
"""
_shortname = "null"
numeric_type = float
@classmethod
def _abstract_eval(cls, *_, **__):
return (), float
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