KrylovQuantumClassical

KrylovQuantumClassical is the software used for the numerical computations presented in the article:

From phase space to Krylov space, one shell at a time, De Ro, N., Sánchez-Garrido, A., and Sonner, J. (2026). [preprint]

Please cite this article if you use (a part of) this software for a publication.

This work develops a framework for classical Krylov complexity and investigates its connection with the well-established notion of quantum Krylov complexity. We derive a semiclassical correspondence between the classical and quantum regimes as well as a Krylov–Ehrenfest theorem. We also introduce a microcanonical formulation of Krylov complexity, in which Krylov dynamics unfolds within fixed-energy shells. These ideas are illustrated using the Lipkin–Meshkov–Glick and Feingold–Peres collective spin models, both of which possess a well-defined classical limit in the large-spin limit.