Source code for qiskit_algorithms.time_evolvers.classical_methods.scipy_imaginary_evolver

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"""Classical Quantum Imaginary Time Evolution."""

from ..time_evolution_problem import TimeEvolutionProblem
from ..time_evolution_result import TimeEvolutionResult
from ..imaginary_time_evolver import ImaginaryTimeEvolver
from .evolve import _evolve

[docs]class SciPyImaginaryEvolver(ImaginaryTimeEvolver): r"""Classical Evolver for imaginary time evolution. Evolves an initial state :math:`|\Psi\rangle` for an imaginary time :math:`\tau = it` under a Hamiltonian :math:`H`, as provided in the ``evolution_problem``. Note that the precision of the evolver does not depend on the number of timesteps taken. """ def __init__(self, num_timesteps: int): r""" Args: num_timesteps: The number of timesteps in the simulation. Raises: ValueError: If `num_timesteps` is not a positive integer. """ self.num_timesteps = num_timesteps
[docs] def evolve(self, evolution_problem: TimeEvolutionProblem) -> TimeEvolutionResult: r"""Perform imaginary time evolution :math:`\exp(-\tau H)|\Psi\rangle`. Evolves an initial state :math:`|\Psi\rangle` for an imaginary time :math:`\tau` under a Hamiltonian :math:`H`, as provided in the ``evolution_problem``. Args: evolution_problem: The definition of the evolution problem. Returns: Evolution result which includes an evolved quantum state. """ return _evolve(evolution_problem, self.num_timesteps, real_time=False)