Source code for

# This code is part of a Qiskit project.
# (C) Copyright IBM 2021, 2023.
# This code is licensed under the Apache License, Version 2.0. You may
# obtain a copy of this license in the LICENSE.txt file in the root directory
# of this source tree or at
# Any modifications or derivative works of this code must retain this
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"""The ParticleNumber property."""

from __future__ import annotations

from typing import Mapping

import qiskit_nature  # pylint: disable=unused-import
from qiskit_nature.second_q.operators import FermionicOp

[docs]class ParticleNumber: """The ParticleNumber property. The following attributes can be set via the initializer but can also be read and updated once the ``ParticleNumber`` object has been constructed. Attributes: num_spatial_orbitals (int): the number of spatial orbitals. """ def __init__(self, num_spatial_orbitals: int) -> None: """ Args: num_spatial_orbitals: the number of spatial orbitals in the system. """ self.num_spatial_orbitals = num_spatial_orbitals
[docs] def second_q_ops(self) -> Mapping[str, FermionicOp]: """Returns the second quantized particle number operator. Returns: A mapping of strings to `FermionicOp` objects. """ num_spin_orbitals = 2 * self.num_spatial_orbitals op = FermionicOp( {f"+_{o} -_{o}": 1.0 for o in range(num_spin_orbitals)}, num_spin_orbitals=num_spin_orbitals, ) return {self.__class__.__name__: op}
[docs] def interpret( self, result: "qiskit_nature.second_q.problems.EigenstateResult" # type: ignore[name-defined] ) -> None: """Interprets an :class:`~qiskit_nature.second_q.problems.EigenstateResult` in this property's context. Args: result: the result to add meaning to. """ result.num_particles = [] if result.aux_operators_evaluated is None: return for aux_op_eigenvalues in result.aux_operators_evaluated: if not isinstance(aux_op_eigenvalues, dict): continue _key = self.__class__.__name__ if aux_op_eigenvalues[_key] is not None: result.num_particles.append(aux_op_eigenvalues[_key].real) else: result.num_particles.append(None)