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Compute the gradients of the expectation values. This method employs a linear combination of unitaries [1].

Reference: [1] Schuld et al., Evaluating analytic gradients on quantum hardware, 2018 arXiv:1811.11184

Parameters
• estimator (BaseEstimator) – The estimator used to compute the gradients.

• derivative_type (DerivativeType) –

The type of derivative. Can be either DerivativeType.REAL DerivativeType.IMAG, or DerivativeType.COMPLEX. Defaults to DerivativeType.REAL.

• 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 $$2 ⟨ψ(ω)|O(θ)|dω ψ(ω)〉$$.

• 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.

Methods

 run Run the job of the estimator gradient on the given circuits. update_default_options Update the gradient's default options setting.

Attributes

SUPPORTED_GATES = ['rx', 'ry', 'rz', 'rzx', 'rzz', 'ryy', 'rxx', 'cx', 'cy', 'cz', 'ccx', 'swap', 'iswap', 'h', 't', 's', 'sdg', 'x', 'y', 'z']
derivative_type

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

Return type

DerivativeType

Returns

The derivative type.

options

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.