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Source code for mrmustard.lab.circuit_components_utils.b_to_ps

# Copyright 2024 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.

"""The class representing an operation that changes Bargmann into phase space."""

from __future__ import annotations

from collections.abc import Sequence

from mrmustard.parameters import Parameter
from mrmustard.physics.ansatz_factory import AnsatzFactory
from mrmustard.physics.wires import ReprEnum, Wires
from mrmustard.utils.typing import ComplexTensor

from ..transformations.base import Map
from .builtins import bargmann_to_wigner

__all__ = ["BtoPS"]




[docs]
class BtoPS(Map):
    r"""The `s`-parametrized Stratonovich-Weyl kernel as a ``Map``.

    Used internally as a ``Channel`` for transformations between representations.

    Args:
        modes: The modes of this channel.
        s: The `s` parameter of this channel. The case `s=-1`  corresponds to Husimi, `s=0` to Wigner, and `s=1` to Glauber P function.
    """

    short_name = "BtoPS"

    def __init__(
        self,
        modes: int | tuple[int, ...],
        s: float,
    ):
        modes = (modes,) if isinstance(modes, int) else modes
        super().__init__(
            ansatz_factory=AnsatzFactory(
                ansatz_dict={ReprEnum.BARGMANN: (bargmann_to_wigner, ("s", "n_modes", "lin_sup"))},
                n_modes=len(modes),
            ),
            wires=Wires(
                modes_in_bra=set(modes),
                modes_out_bra=set(modes),
                modes_in_ket=set(modes),
                modes_out_ket=set(modes),
            ),
            name=self.__class__.__name__,
        )
        self.parameters["s"] = Parameter.from_cc_init(s, "float64", f"{self.name}/s")

        for w in self.wires.output.standard_order:
            w.repr = ReprEnum.PHASESPACE



[docs]
    def fock_array(self, shape: int | Sequence[int] | None = None) -> ComplexTensor:
        raise NotImplementedError(f"{self.__class__.__name__} does not have a Fock representation.")