[v0.99.0] - 2024-03-19

Release Notes

The v0.99 release is the Backwards-compatible version of the v1.0 release. It has all of the same features, but should raise informative warnings for those features that are not compatible with v1.0.

The most notable changes since v0.11 are the addition of VUMPS (variational uniform MPS) algorithms and simulation classes for dynamics and spectral functions.

Changelog

Added

• PR #266 combining several new features

  • Variational Uniform MPS (VUMPS) algorithm SingleSiteVUMPSEngine and TwoSiteVUMPSEngine for the optimization of the new MPS subclass UniformMPS,

  • the MomentumMPS for the quasi-particle excitation ansatz, which can be optimized by PlaneWaveExcitationEngine

  • MPS initialization methods from_random_unitary_evolution() and from_desired_bond_dimension()

  • Overhaul of simulation OrthogonalExcitations and generalization to new TopologicalExcitations, with enhanced handling of segment boundary conditions, e.g. MPS extract_enlarged_segment().

  • GMRES

  • polar() decomposition (based on SVD).

  • BoostNpcLinearOperator that can boost (i.e. add constants) to a linear operator, providing an alternative to the OrthogonalNpcLinearOperator

• Added consistency checks, see consistency_check(), as well as

  • Algorithm.max_N_sites_per_ring

  • TimeEvolutionAlgorithm.max_trunc_err

  • IterativeSweeps.max_trunc_err

  • ExpMPOEvolution.max_dt

  • TEBDEngine.max_delta_t

• Added class SimpleBZ for the Brillouin zone of a Lattice and convenience functions for plotting it.

• Add simulation classes SpectralSimulation, TimeDependentCorrelation, TimeDependentCorrelationEvolveBraKet, SpectralSimulationEvolveBraKet.

• Add module tenpy.simulations.post_processing with a DataLoader class, which can be used at the end of a simulation (or in a separate script) to calculate additional results from measurement data or plot something.

• Functions to perform a linear prediction in tenpy.tools.prediction.

• Functions for fourier transform and plotting of spectral functions in tenpy.tools.spectral_function_tools.

Changed

• safeguard measurements with try-except.

Fixed

• MPO methods dagger(), is_hermitian(), and __add__() now respect the explicit_plus_hc flag.

• Handle Jordan wigner strings better, see PR #355. This includes a new way to add JW signs on a virtual MPS leg via the site’s charge_to_JW_signs()