Source code for qiskit_nature.second_q.circuit.library.ansatzes.uccsd

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The UCCSD Ansatz.

from __future__ import annotations

from qiskit.circuit import QuantumCircuit
from qiskit_nature.second_q.mappers import QubitMapper
from .ucc import UCC

[docs]class UCCSD(UCC): """The UCCSD Ansatz. This is a convenience subclass of the UCC ansatz. For more information refer to :class:`UCC`. """ def __init__( self, num_spatial_orbitals: int | None = None, num_particles: tuple[int, int] | None = None, qubit_mapper: QubitMapper | None = None, *, reps: int = 1, initial_state: QuantumCircuit | None = None, generalized: bool = False, preserve_spin: bool = True, include_imaginary: bool = False, ) -> None: # pylint: disable=unused-argument """ Args: num_spatial_orbitals: The number of spatial orbitals. num_particles: The tuple of the number of alpha- and beta-spin particles. qubit_mapper: The :class:`~qiskit_nature.second_q.mappers.QubitMapper` which takes care of mapping to a qubit operator. reps: The number of times to repeat the evolved operators. initial_state: A ``QuantumCircuit`` object to prepend to the circuit. generalized: Boolean flag whether or not to use generalized excitations, which ignore the occupation of the spin orbitals. As such, the set of generalized excitations is only determined from the number of spin orbitals and independent from the number of particles. preserve_spin: Boolean flag whether or not to preserve the particle spins. include_imaginary: Boolean flag which when set to ``True`` expands the ansatz to include imaginary parts using twice the number of free parameters. """ super().__init__( num_spatial_orbitals=num_spatial_orbitals, num_particles=num_particles, excitations="sd", qubit_mapper=qubit_mapper, alpha_spin=True, beta_spin=True, max_spin_excitation=None, generalized=generalized, preserve_spin=preserve_spin, include_imaginary=include_imaginary, reps=reps, initial_state=initial_state, )