qiskit.opflow.gradients.Hessian¶

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

Compute the Hessian of an expected value.

매개변수

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

예외

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

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

매개변수

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

예외

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)[소스]¶

매개변수

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.

반환값

An operator whose evaluation yields the Hessian

반환 형식

OperatorBase

get_hessian(operator, params=None)[소스]¶

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

매개변수

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.

반환 형식

OperatorBase

반환값

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

예외

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.

매개변수

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.

반환값

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

반환 형식

callable(param_values)

property hess_method¶

Returns CircuitGradient.

반환 형식: CircuitGradient
반환값: CircuitGradient.

static parameter_expression_grad(param_expr, param)¶

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

매개변수

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

반환 형식

Union[ParameterExpression, float]

반환값

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