# 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
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from __future__ import annotations
from typing import List, Sequence, Union
from braket.circuits.quantum_operator import QuantumOperator
[docs]class Observable(QuantumOperator):
"""
Class `Observable` to represent a quantum observable.
Objects of this type can be used as input to `ResultType.Sample`, `ResultType.Variance`,
`ResultType.Expectation` to specify the measurement basis.
"""
def __init__(self, qubit_count: int, ascii_symbols: Sequence[str]):
super().__init__(qubit_count=qubit_count, ascii_symbols=ascii_symbols)
[docs] def to_ir(self) -> List[Union[str, List[List[List[float]]]]]:
"""List[Union[str, List[List[List[float]]]]]: Returns the IR
representation for the observable"""
raise NotImplementedError
[docs] @classmethod
def register_observable(cls, observable: Observable):
"""Register an observable implementation by adding it into the Observable class.
Args:
observable (Observable): Observable class to register.
"""
setattr(cls, observable.__name__, observable)
def __matmul__(self, other) -> Observable.TensorProduct:
if isinstance(other, Observable.TensorProduct):
return other.__rmatmul__(self)
if isinstance(other, Observable):
return Observable.TensorProduct([self, other])
raise ValueError("Can only perform tensor products between observables.")
def __repr__(self) -> str:
return f"{self.name}('qubit_count': {self.qubit_count})"
def __eq__(self, other) -> bool:
if isinstance(other, Observable):
return self.name == other.name
return NotImplemented