# Source code for pennylane.ops

# Copyright 2018 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.
#pylint: disable=too-few-public-methods,function-redefined
"""
This module contains core quantum operations supported by PennyLane -
such as gates, state preparations and observables.
"""
from pennylane.operation import Any, Observable, CVObservable
from .cv import *
from .qubit import *
from .cv import __all__ as _cv__all__
from .cv import ops as _cv__ops__
from .cv import obs as _cv__obs__
from .qubit import __all__ as _qubit__all__
from .qubit import ops as _qubit__ops__
from .qubit import obs as _qubit__obs__
[docs]class Identity(CVObservable, Observable):
r"""pennylane.Identity(wires)
The identity observable :math:`\I`.
The expectation of this observable
.. math::
E[\I] = \text{Tr}(\I \rho)
corresponds to the trace of the quantum state, which in exact
simulators should always be equal to 1.
"""
num_wires = Any
num_params = 0
par_domain = None
grad_method = None
ev_order = None
__all__ = _cv__all__ + _qubit__all__ + ["Identity"]
__all_ops__ = list(_cv__ops__ | _qubit__ops__)
__all_obs__ = list(_cv__obs__ | _qubit__obs__) + ["Identity"]