Krylov complexity has it all

Fuente: arXiv
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Main Author: Mück, Wolfgang
Format: Preprint
Published: 2026
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author Mück, Wolfgang
author_facet Mück, Wolfgang
contents This paper establishes that Krylov complexity contains the entire information about the dynamics of a quantum operator, extending the list of equivalent quantities that can serve this purpose, such as the Lanczos coefficients, the return amplitude, and the spectral density. To demonstrate this equivalence, an explicit recursive algorithm is constructed to calculate Lanczos coefficients from the Taylor expansion of the Krylov complexity around $t=0$. Furthermore, the paper discusses the distinction between Krylov and spread complexity, clarifying why a similar recursive algorithm cannot exist for the latter without additional dynamical input. These results provide a ``proof of principle'' for using Krylov complexity as a complete characterization of operator evolution in quantum systems.
format Preprint
id arxiv_https___arxiv_org_abs_2605_28681
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Krylov complexity has it all
Mück, Wolfgang
High Energy Physics - Theory
Quantum Physics
This paper establishes that Krylov complexity contains the entire information about the dynamics of a quantum operator, extending the list of equivalent quantities that can serve this purpose, such as the Lanczos coefficients, the return amplitude, and the spectral density. To demonstrate this equivalence, an explicit recursive algorithm is constructed to calculate Lanczos coefficients from the Taylor expansion of the Krylov complexity around $t=0$. Furthermore, the paper discusses the distinction between Krylov and spread complexity, clarifying why a similar recursive algorithm cannot exist for the latter without additional dynamical input. These results provide a ``proof of principle'' for using Krylov complexity as a complete characterization of operator evolution in quantum systems.
title Krylov complexity has it all
topic High Energy Physics - Theory
Quantum Physics
url https://arxiv.org/abs/2605.28681