[v1.1.1] - 2026-07-28

Release Notes

Small changes and additions and several minor bugfixes.

Support MPS with unknown singular values, i.e. with None in mps._S.
Add tenpy.networks.mpo.MPO.from_Wflat().
Add ArnoldiEvolution, similar to LanczosEvolution, to support evolution under non-Hermitian effective Hamiltonians
Enable TDVP with non-Hermitian Hamiltonians, see PR #625

Improved tenpy.algorithms.exact_diag.get_numpy_Hamiltonian() by setting the cutoff for exponentially decaying terms to 0 (increasing accuracy)
Add explicit normalizations during canonical_form_finite() that stabilize it for MPS with small norm, see issue #596.

Fixed an error where TDVP did not correctly handle explicit_plus_hc. Before, the flag was considered in the two-site update, but ignored in the one-site update for TwoSiteTDVP. For SingleSiteTDVP, it was considered in the one-site update, but ignored in the zero-site update. Using a model with explicit_plus_hc in TDVP thus led to an incorrect computation. However, in the test cases we used, this led to a barrage of loud warnings from the Lanczos evolution, so it is unlikely that errors from this went unnoticed.
Fix typo in the computation of the unit_cell_width during extract_segment().
Fix hdf5 loading for MPS and MPO. The implementations were not backwards compatible and could not load files from tenpy<1.1.0
Fix bug in tenpy.linalg.charges.LegCharge.from_drop_charges() where string inputs were not handled correctly, see issue #626
Fix the sign convention for the Haldane FCI example.