qiskit.algorithms.VQE.construct_expectation

VQE.construct_expectation(parameter, operator, return_expectation=False)

Generate the ansatz circuit and expectation value measurement, and return their runnable composition.

Parameters

• parameter (Union[List[float], List[Parameter], ndarray]) – Parameters for the ansatz circuit.

• operator (OperatorBase) – Qubit operator of the Observable

• return_expectation (bool) – If True, return the ExpectationBase expectation converter used in the construction of the expectation value. Useful e.g. to compute the standard deviation of the expectation value.

Return type

Union[OperatorBase, Tuple[OperatorBase, ExpectationBase]]

Returns

The Operator equalling the measurement of the ansatz StateFn by the Observable’s expectation StateFn, and, optionally, the expectation converter.

Raises

• AlgorithmError – If no operator has been provided.

• AlgorithmError – If no expectation is passed and None could be inferred via the ExpectationFactory.