Potential energy surface samplers (qiskit.chemistry.algorithms.pes_samplers)¶

Potential energy surface samplers.

Algorithms that can compute potential energy surfaces.

 BOPESSampler Class to evaluate the Born-Oppenheimer Potential Energy Surface (BOPES).

When used with variational solvers, such as VQE, when computing a set of points there is support for extrapolation from prior solution(s) to bootstrap the algorithm with a better starting point to facilitate convergence. Extrapolators are:

 Extrapolator This class is based on performing extrapolation of parameters of a wavefunction for a variational algorithm defined in the variational forms as part of the Qiskit Aqua module. DifferentialExtrapolator An extrapolator based on treating each param set as a point in space, and fitting a Hamiltonian which evolves each point to the next. PCAExtrapolator A wrapper extrapolator which reduces the points’ dimensionality with PCA, performs extrapolation in the transformed pca space, and inverse transforms the results before returning. PolynomialExtrapolator An extrapolator based on fitting each parameter to a polynomial function of a user-specified degree. SieveExtrapolator A wrapper extrapolator which clusters the parameter values - either before extrapolation, after, or both - into two large and small clusters, and sets the small clusters’ parameters to zero. WindowExtrapolator An extrapolator which wraps another extrapolator, limiting the internal extrapolator’s ground truth parameter set to a fixed window size.

There is also a set of support function for potentials:

 EnergySurface1DSpline A simple cubic spline interpolation for the potential energy surface. HarmonicPotential Implements a 1D Harmonic potential. MorsePotential Implements a 1D Morse potential. EnergySurfaceBase Class to hold a potential energy surface PotentialBase Class to hold prescribed 1D potentials (e.g. VibronicStructureBase Class to hold a molecular vibronic structure providing access to vibrational modes and energy levels.