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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]

Deprecated

  • Deprecated the ignored atol and eps arguments of direct_greens_function. They will be removed in version 2.4.0.
  • Deprecated solver_options["atol"] and solver_options["eps"] for the implicit direct solver. They will be removed in version 2.4.0.
  • Deprecated the legacy one-argument custom Sylvester callback form solve_sylvester(Y). Use solve_sylvester(Y, index) instead. The legacy form will be removed in version 2.4.0.

Changed

  • Reworked the implicit direct solver to constrain known degenerate kernels using QR-selected pivot equations instead of relying on MUMPS singularity detection, and added a SciPy sparse-LU fallback when python-mumps is unavailable.

Added

  • Added a non-Hermitian similarity-transform algorithm via block_diagonalize(..., hermitian=False), including support for asymmetric selective masks, symbolic inputs, and biorthogonal subspace_eigenvectors=[(right, left), ...] in the explicit and implicit direct paths. The implicit KPM solver remains unsupported in the non-Hermitian path.

[2.2.1] - 2026-03-09

Added

Changed

  • Made python-mumps an optional dependency, only required for the implicit solver.
  • When SymPy cannot determine whether an off-diagonal zeroth-order block is zero, emit a warning and proceed instead of erroring.

Removed

  • Dropped support for Python 3.11, numpy 1.26, and scipy 1.12 according to the SPEC-0.

[2.2.0] - 2025-06-05

Added

  • Added a reference implementation of arbitrary order Schrieffer-Wolff transformation to the documentation and a comparison of its convergence radius with Pymablock algorithm.
  • Added support for bosonic, fermionic, spin, and ladder (Floquet) second-quantized Hamiltonians in the operator formalism.
  • Added a tutorial on the Rabi model with a periodic drive.
  • Added documentation for the second quantization formalism.
  • Added a comparison with Schrieffer-Wolff and a demonstration of the convergence radius.

Changed

  • If the Hamiltonian contains only one block, fully_diagonalize can be provided as value instead of {0: value}.
  • Updated the dispersive shift tutorial to include the second quantization approach.
  • Updated the Jaynes-Cummings tutorial to the new second quantization API.

Removed

  • Dropped support for Numpy 1.25, Scipy 1.11, and Sympy 1.12 according to the SPEC-0.

[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.