qiskit.opflow.gradients.Hessian¶

class Hessian(hess_method='param_shift', **kwargs)[ソース]¶

Compute the Hessian of an expected value.

パラメータ

hess_method (Union[str, CircuitGradient]) – 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

例外

ValueError – If method != fin_diff and epsilon is not None.

__init__(hess_method='param_shift', **kwargs)¶

パラメータ

hess_method (Union[str, CircuitGradient]) – 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

例外

ValueError – If method != fin_diff and epsilon is not None.

Methods

`__init__`([hess_method])	type hess_method `Union`[`str`, `CircuitGradient`]
`convert`(operator[, params])	type operator `OperatorBase`
`get_hessian`(operator[, params])	Get the Hessian for the given operator w.r.t.
`gradient_wrapper`(operator, bind_params[, …])	Get a callable function which provides the respective gradient, Hessian or QFI for given parameter values.
`parameter_expression_grad`(param_expr, param)	Get the derivative of a parameter expression w.r.t.

Attributes

hess_method

Returns CircuitGradient.

convert(operator, params=None)[ソース]¶

パラメータ

operator (OperatorBase) – The operator for which we compute the Hessian
params (Union[Tuple[ParameterExpression, ParameterExpression], List[Tuple[ParameterExpression, ParameterExpression]], List[ParameterExpression], ParameterVector, None]) – The parameters we are computing the Hessian with respect to Either give directly the tuples/list of tuples for which the second order derivative is to be computed or give a list of parameters to build the full Hessian for those parameters. If not explicitly passed, the full Hessian is constructed. The parameters are then inferred from the operator and sorted by name.

戻り値

An operator whose evaluation yields the Hessian

戻り値の型

OperatorBase

get_hessian(operator, params=None)[ソース]¶

Get the Hessian for the given operator w.r.t. the given parameters

パラメータ

operator (OperatorBase) – Operator w.r.t. which we take the Hessian.
params (Union[Tuple[ParameterExpression, ParameterExpression], List[Tuple[ParameterExpression, ParameterExpression]], List[ParameterExpression], ParameterVector, None]) – Parameters w.r.t. which we compute the Hessian. If not explicitly passed, the full Hessian is constructed. The parameters are then inferred from the operator and sorted by name.

戻り値の型

OperatorBase

戻り値

Operator which represents the gradient w.r.t. the given params.

例外

ValueError – If params contains a parameter not present in operator.
ValueError – If operator is not parameterized.
OpflowError – If the coefficient of the operator could not be reduced to 1.
OpflowError – If the differentiation of a combo_fn requires JAX but the package is not installed.
TypeError – If the operator does not include a StateFn given by a quantum circuit
TypeError – If the parameters were given in an unsupported format.
Exception – Unintended code is reached
MissingOptionalLibraryError – jax not installed

gradient_wrapper(operator, bind_params, grad_params=None, backend=None)¶

Get a callable function which provides the respective gradient, Hessian or QFI for given parameter values. This callable can be used as gradient function for optimizers.

パラメータ

operator (OperatorBase) – The operator for which we want to get the gradient, Hessian or QFI.
bind_params (Union[ParameterExpression, ParameterVector, List[ParameterExpression]]) – The operator parameters to which the parameter values are assigned.
grad_params (Union[ParameterExpression, ParameterVector, List[ParameterExpression], Tuple[ParameterExpression, ParameterExpression], List[Tuple[ParameterExpression, ParameterExpression]], None]) – The parameters with respect to which we are taking the gradient, Hessian or QFI. If grad_params = None, then grad_params = bind_params
backend (Union[BaseBackend, QuantumInstance, None]) – The quantum backend or QuantumInstance to use to evaluate the gradient, Hessian or QFI.

戻り値

Function to compute a gradient, Hessian or QFI. The function takes an iterable as argument which holds the parameter values.

戻り値の型

callable(param_values)

property hess_method¶

Returns CircuitGradient.

戻り値の型: CircuitGradient
戻り値: CircuitGradient.

static parameter_expression_grad(param_expr, param)¶

Get the derivative of a parameter expression w.r.t. the given parameter.

パラメータ

param_expr (ParameterExpression) – The Parameter Expression for which we compute the derivative
param (ParameterExpression) – Parameter w.r.t. which we want to take the derivative

戻り値の型

Union[ParameterExpression, float]

戻り値

ParameterExpression representing the gradient of param_expr w.r.t. param