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CHANGELOG.md

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Changelog

All notable changes to this project will be documented in this file.

The format is based on Keep a Changelog, and this project adheres to Semantic Versioning.

[Unreleased]

[2.1.0] - 2024-11-19

Added

  • Generalized the algorithm to support an arbitrary number of blocks. To specify multiple blocks, provide either a list with eigenvectors of each block in subspace_eigenvectors, or a list marking to which block each basis state belongs in subspace_indices.
  • Implemented full diagonalization of the Hamiltonian within blocks except for degenerate eigensubspaces. In case of one block with non-degenerate eigenvalues, this implements the Rayleigh-Schrödinger perturbation theory.
  • Implemented selective diagonalization of the Hamiltonian within blocks, which can eliminate any subset of the off-diagonal elements within a block.
  • Implemented functionality for making optimized series algorithms, see {autolink}~pymablock.algorithm_parsing.series_computation and a domain-specific language to define those. This is an advanced and an experimental feature, subject to change.
  • Added a function operator_to_BlockSeries to transform operators to the same representation as the Hamiltonian, and illustrated its use in the tutorial.
  • Included a tutorial on how to manipulate complex symbolic Hamiltonians and demonstrate multi-block diagonalization.
  • Included a tutorial on how to compute the dispersive shift in a transmon-resonator system.

Changed

  • Auxiliary vectors for the implicit KPM solver should now be passed using solver_options["aux_vectors"] rather than as the last entry in subspace_eigenvectors.

Improved

  • Further reduced the number of matrix products by around 30% for high orders and down to a guaranteed minimum for 3rd order.
  • Improved the efficiency of the MUMPS solver on real Hamiltonians.
  • Allowed subspaces to have degenerate eigenvalues if the corresponding energy denominators are never used. This may happen in multiblock perturbation theory.

Fixed

  • Fix incorrect shape of {autolink}~pymablock.BlockSeries blocks if $H_0$ has a zero block (#127).

Removed

  • Dropped support for Python 3.10 and sympy 1.11 according to the SPEC-0.

[2.0.0] - 2024-02-03

Improved

  • Switched to the python-mumps wrapper for the direct solver, which is available on all platforms and is more feature-complete.
  • The implicit KPM solver now guarantees reaching a requested accuracy.
  • A new algorithm that has optimal scaling while avoiding multiplication by $H_0$, and supports implicit data. This combines advantages of all previous algorithms, and therefore supersedes them.
  • Sped up {autolink}~pymablock.series.cauchy_dot_product when there are more than 3 series by reusing intermediate results.
  • Optimized memory usage of ~pymablock.block_diagonalize by deleting intermediate results when they are no longer needed.

Added

  • A complete description of the algorithm to the documentation, see documentation.
  • String representation of {autolink}~pymablock.BlockSeries for readability.

Removed

  • expanded, symbolic, implicit, and general functions and algorithms (functionality taken over by the new general algorithm, with {autolink}~pymablock.block_diagonalize the main interface).
  • the algorithm argument from {autolink}~pymablock.block_diagonalize (there is only one algorithm now).
  • exclude_last argument of {autolink}~pymablock.series.cauchy_dot_product (instead we check whtether other terms lack 0th order).

[1.0.0] - 2023-06-05

  • First release of Pymablock.