ImaginaryMcLachlanPrinciple

class ImaginaryMcLachlanPrinciple(qgt=None, gradient=None)

Bases: ImaginaryVariationalPrinciple

Class for an Imaginary McLachlan’s Variational Principle. It aims to minimize the distance between both sides of the Wick-rotated Schrödinger equation with a quantum state given as a parametrized trial state. The principle leads to a system of linear equations handled by a linear solver. The imaginary variant means that we consider imaginary time dynamics.

Parameters

• qgt (BaseQGT | None) – Instance of a the GQT class used to compute the QFI. If None provided, LinCombQGT is used.

• gradient (BaseEstimatorGradient | None) – Instance of a class used to compute the state gradient. If None provided, LinCombEstimatorGradient is used.

Raises

AlgorithmError – If the gradient instance does not contain an estimator.

Methods Defined Here

evolution_gradient

Calculates an evolution gradient according to the rules of this variational principle.