qiskit.aqua.operators.gradients.Hessian¶

class Hessian(hess_method='param_shift', **kwargs)[código fonte]¶

Compute the Hessian of an expected value.

Parâmetros

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

Levanta

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

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

Parâmetros

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

Levanta

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)[código fonte]¶

Parâmetros

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.

Retorna

An operator whose evaluation yields the Hessian

Tipo de retorno

OperatorBase

Levanta

ValueError – If params is not set.

get_hessian(operator, params=None)[código fonte]¶

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

Parâmetros

operator (OperatorBase) – Operator w.r.t. which we take the Hessian.
params (Union[Tuple[ParameterExpression, ParameterExpression], List[Tuple[ParameterExpression, ParameterExpression]], None]) – Parameters w.r.t. which we compute the Hessian.

Tipo de retorno

OperatorBase

Retorna

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

Levanta

ValueError – If params contains a parameter not present in operator.
AquaError – If the coefficient of the operator could not be reduced to 1. AquaError: 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

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.

Parâmetros

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.

Retorna

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

Tipo de retorno

callable(param_values)

property hess_method¶

Returns CircuitGradient.

Tipo de retorno: CircuitGradient
Retorna: CircuitGradient.

static parameter_expression_grad(param_expr, param)¶

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

Parâmetros

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

Tipo de retorno

Union[ParameterExpression, float]

Retorna

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