qiskit.algorithms.QAOA.get_energy_evaluation

QAOA.get_energy_evaluation(operator, return_expectation=False)

Returns a function handle to evaluates the energy at given parameters for the ansatz.

This is the objective function to be passed to the optimizer that is used for evaluation.

Parameters

• operator (OperatorBase) – The operator whose energy to evaluate.

• return_expectation (bool) – If True, return the ExpectationBase expectation converter used in the construction of the expectation value. Useful e.g. to evaluate other operators with the same expectation value converter.

Return type

Callable[[ndarray], Union[float, List[float]]]

Returns

Energy of the hamiltonian of each parameter, and, optionally, the expectation converter.

Raises

RuntimeError – If the circuit is not parameterized (i.e. has 0 free parameters).