Coverage for src/braket/circuits/observable.py : 100%

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1# Copyright 2019-2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
2#
3# Licensed under the Apache License, Version 2.0 (the "License"). You
4# may not use this file except in compliance with the License. A copy of
5# the License is located at
6#
7# http://aws.amazon.com/apache2.0/
8#
9# or in the "license" file accompanying this file. This file is
10# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
11# ANY KIND, either express or implied. See the License for the specific
12# language governing permissions and limitations under the License.
13from __future__ import annotations
15from typing import List, Sequence, Union
17from braket.circuits.quantum_operator import QuantumOperator
20class Observable(QuantumOperator):
21 """
22 Class `Observable` to represent a quantum observable.
24 Objects of this type can be used as input to `ResultType.Sample`, `ResultType.Variance`,
25 `ResultType.Expectation` to specify the measurement basis.
26 """
28 def __init__(self, qubit_count: int, ascii_symbols: Sequence[str]):
29 super().__init__(qubit_count=qubit_count, ascii_symbols=ascii_symbols)
31 def to_ir(self) -> List[Union[str, List[List[List[float]]]]]:
32 """List[Union[str, List[List[List[float]]]]]: Returns the IR
33 representation for the observable"""
34 raise NotImplementedError
36 @classmethod
37 def register_observable(cls, observable: Observable):
38 """Register an observable implementation by adding it into the Observable class.
40 Args:
41 observable (Observable): Observable class to register.
42 """
43 setattr(cls, observable.__name__, observable)
45 def __matmul__(self, other) -> Observable.TensorProduct:
46 if isinstance(other, Observable.TensorProduct):
47 return other.__rmatmul__(self)
49 if isinstance(other, Observable):
50 return Observable.TensorProduct([self, other])
52 raise ValueError("Can only perform tensor products between observables.")
54 def __repr__(self) -> str:
55 return f"{self.name}('qubit_count': {self.qubit_count})"
57 def __eq__(self, other) -> bool:
58 if isinstance(other, Observable):
59 return self.name == other.name
60 return NotImplemented