ParamShiftEstimatorGradient

class ParamShiftEstimatorGradient(estimator, options=None, derivative_type=DerivativeType.REAL)

Bases: qiskit.algorithms.gradients.base_estimator_gradient.BaseEstimatorGradient

Compute the gradients of the expectation values by the parameter shift rule [1].

Reference: [1] Schuld, M., Bergholm, V., Gogolin, C., Izaac, J., and Killoran, N. Evaluating analytic gradients on quantum hardware, DOI

Parameters

$estimator (BaseEstimator) - The estimator used to compute the gradients.$
$options (Options | None) - Primitive backend runtime options used for circuit execution. The order of priority is: options in run method > gradient’s default options > primitive’s default setting. Higher priority setting overrides lower priority setting$
derivative_type (DerivativeType) –

The type of derivative. Can be either DerivativeType.REAL DerivativeType.IMAG, or DerivativeType.COMPLEX.
- DerivativeType.REAL computes $2 \mathrm{Re}[⟨ψ(ω)|O(θ)|dω ψ(ω)〉]$ .
- DerivativeType.IMAG computes $2 \mathrm{Im}[⟨ψ(ω)|O(θ)|dω ψ(ω)〉]$ .
- DerivativeType.COMPLEX computes $2 ⟨ψ(ω)|O(θ)|dω ψ(ω)〉$ .
Defaults to DerivativeType.REAL, as this yields e.g. the commonly-used energy gradient and this type is the only supported type for function-level schemes like finite difference.

Methods

ParamShiftEstimatorGradient.run(circuits, observables, parameter_values, parameters=None, **options)

Run the job of the estimator gradient on the given circuits.

Parameters

circuits – The list of quantum circuits to compute the gradients.
observables – The list of observables.
parameter_values – The list of parameter values to be bound to the circuit.
parameters – The sequence of parameters to calculate only the gradients of the specified parameters. Each sequence of parameters corresponds to a circuit in circuits. Defaults to None, which means that the gradients of all parameters in each circuit are calculated.
options – Primitive backend runtime options used for circuit execution. The order of priority is: options in run method > gradient’s default options > primitive’s default setting. Higher priority setting overrides lower priority setting

Returns

The job object of the gradients of the expectation values. The i-th result corresponds to circuits[i] evaluated with parameters bound as parameter_values[i] . The j-th element of the i-th result corresponds to the gradient of the i-th circuit with respect to the j-th parameter.

Raises

ValueError - Invalid arguments are given.

ParamShiftEstimatorGradient.update_default_options(**options)

Update the gradient’s default options setting.

Parameters

**options - The fields to update the default options.

Default value: ['x', 'y', 'z', 'h', 'rx', 'ry', 'rz', 'p', 'cx', 'cy', 'cz', 'ryy', 'rxx', 'rzz', 'rzx']

Return the derivative type (real, imaginary or complex).

Return type

DerivativeType

Returns

The derivative type.

Return the union of estimator options setting and gradient default options, where, if the same field is set in both, the gradient’s default options override the primitive’s default setting.

Return type

Options

Returns

The gradient default + estimator options.

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