C贸digo fuente para qiskit.opflow.gradients.hessian_base

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"""The module to compute Hessians."""

from typing import Union

from qiskit.utils.deprecation import deprecate_func
from .circuit_gradients.circuit_gradient import CircuitGradient
from .derivative_base import DerivativeBase

[documentos]class HessianBase(DerivativeBase): """Deprecated: Base class for the Hessian of an expected value.""" @deprecate_func( since="0.24.0", additional_msg="For code migration guidelines, visit https://qisk.it/opflow_migration.", ) def __init__(self, hess_method: Union[str, CircuitGradient] = "param_shift", **kwargs): r""" Args: hess_method: The method used to compute the state/probability gradient. Can be either ``'param_shift'`` or ``'lin_comb'`` or ``'fin_diff'``. Ignored for gradients w.r.t observable parameters. kwargs (dict): Optional parameters for a CircuitGradient Raises: ValueError: If method != ``fin_diff`` and ``epsilon`` is not None. """ super().__init__() if isinstance(hess_method, CircuitGradient): self._hess_method = hess_method elif hess_method == "param_shift": from .circuit_gradients import ParamShift self._hess_method = ParamShift() elif hess_method == "fin_diff": from .circuit_gradients import ParamShift epsilon = kwargs.get("epsilon", 1e-6) self._hess_method = ParamShift(analytic=False, epsilon=epsilon) elif hess_method == "lin_comb": from .circuit_gradients import LinComb self._hess_method = LinComb() else: raise ValueError( "Unrecognized input provided for `hess_method`. Please provide" " a CircuitGradient object or one of the pre-defined string" " arguments: {'param_shift', 'fin_diff', 'lin_comb'}. " ) @property def hess_method(self) -> CircuitGradient: """Returns ``CircuitGradient``. Returns: ``CircuitGradient``. """ return self._hess_method