qiskit.aqua.operators.gradients.Gradient¶

class Gradient(grad_method='param_shift', **kwargs)[source]¶

Convert an operator expression to the first-order gradient.

Paramètres

grad_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

Lève

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

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

Paramètres

grad_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

Lève

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

Methods

`__init__`([grad_method])	type grad_method `Union`[`str`, `CircuitGradient`]
`convert`(operator[, params])	type operator `OperatorBase`
`get_gradient`(operator, params)	Get the gradient 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

grad_method

Returns CircuitGradient.

convert(operator, params=None)[source]¶

Paramètres

operator (OperatorBase) – The operator we are taking the gradient of.
params (Union[ParameterVector, ParameterExpression, List[ParameterExpression], None]) – params: The parameters we are taking the gradient with respect to.

Type renvoyé

OperatorBase

Renvoie

An operator whose evaluation yields the Gradient.

Lève

ValueError – If params contains a parameter not present in operator.

get_gradient(operator, params)[source]¶

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

Paramètres

operator (OperatorBase) – Operator w.r.t. which we take the gradient.
params (Union[ParameterExpression, ParameterVector, List[ParameterExpression]]) – Parameters w.r.t. which we compute the gradient.

Type renvoyé

OperatorBase

Renvoie

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

Lève

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
Exception – Unintended code is reached

property grad_method¶

Returns CircuitGradient.

Type renvoyé: CircuitGradient
Renvoie: CircuitGradient.

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.

Paramètres

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.

Renvoie

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

Type renvoyé

callable(param_values)

static parameter_expression_grad(param_expr, param)¶

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

Paramètres

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

Type renvoyé

Union[ParameterExpression, float]

Renvoie

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