Krylov complexity as an order parameter for quantum chaotic-integrable transitions

Krylov complexity has recently emerged as a new paradigm to characterize quantum chaos in many-body systems. However, which features of Krylov complexity are a prerogative of quantum chaotic systems and how they relate to more standard probes, such as spectral statistics or out-of-time-order correla...

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Main Authors: Matteo Baggioli, Kyoung-Bum Huh, Hyun-Sik Jeong, Keun-Young Kim, Juan F. Pedraza
Format: Article
Language:English
Published: American Physical Society 2025-04-01
Series:Physical Review Research
Online Access:http://doi.org/10.1103/PhysRevResearch.7.023028
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author Matteo Baggioli
Kyoung-Bum Huh
Hyun-Sik Jeong
Keun-Young Kim
Juan F. Pedraza
author_facet Matteo Baggioli
Kyoung-Bum Huh
Hyun-Sik Jeong
Keun-Young Kim
Juan F. Pedraza
author_sort Matteo Baggioli
collection DOAJ
description Krylov complexity has recently emerged as a new paradigm to characterize quantum chaos in many-body systems. However, which features of Krylov complexity are a prerogative of quantum chaotic systems and how they relate to more standard probes, such as spectral statistics or out-of-time-order correlators (OTOCs), remain open questions. Recent insights have revealed that in quantum chaotic systems Krylov state complexity exhibits a distinct peak during time evolution before settling into a well-understood late-time plateau. In this work we propose that this Krylov complexity peak (KCP) is a hallmark of quantum chaotic systems and suggest that its height could serve as an order parameter for quantum chaos. We demonstrate that the KCP effectively identifies chaotic-integrable transitions in two representative quantum-mechanical models at both infinite and finite temperature: the mass-deformed Sachdev-Ye-Kitaev model and the sparse Sachdev-Ye-Kitaev model. Our findings align with established results from spectral statistics and OTOCs while introducing an operator-independent diagnostic for quantum chaos, offering more universal insights and a deeper understanding of the general properties of quantum chaotic systems.
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spelling doaj-art-c97b2d0ba6e2425daa098c76fa825e442025-08-20T03:17:59ZengAmerican Physical SocietyPhysical Review Research2643-15642025-04-017202302810.1103/PhysRevResearch.7.023028Krylov complexity as an order parameter for quantum chaotic-integrable transitionsMatteo BaggioliKyoung-Bum HuhHyun-Sik JeongKeun-Young KimJuan F. PedrazaKrylov complexity has recently emerged as a new paradigm to characterize quantum chaos in many-body systems. However, which features of Krylov complexity are a prerogative of quantum chaotic systems and how they relate to more standard probes, such as spectral statistics or out-of-time-order correlators (OTOCs), remain open questions. Recent insights have revealed that in quantum chaotic systems Krylov state complexity exhibits a distinct peak during time evolution before settling into a well-understood late-time plateau. In this work we propose that this Krylov complexity peak (KCP) is a hallmark of quantum chaotic systems and suggest that its height could serve as an order parameter for quantum chaos. We demonstrate that the KCP effectively identifies chaotic-integrable transitions in two representative quantum-mechanical models at both infinite and finite temperature: the mass-deformed Sachdev-Ye-Kitaev model and the sparse Sachdev-Ye-Kitaev model. Our findings align with established results from spectral statistics and OTOCs while introducing an operator-independent diagnostic for quantum chaos, offering more universal insights and a deeper understanding of the general properties of quantum chaotic systems.http://doi.org/10.1103/PhysRevResearch.7.023028
spellingShingle Matteo Baggioli
Kyoung-Bum Huh
Hyun-Sik Jeong
Keun-Young Kim
Juan F. Pedraza
Krylov complexity as an order parameter for quantum chaotic-integrable transitions
Physical Review Research
title Krylov complexity as an order parameter for quantum chaotic-integrable transitions
title_full Krylov complexity as an order parameter for quantum chaotic-integrable transitions
title_fullStr Krylov complexity as an order parameter for quantum chaotic-integrable transitions
title_full_unstemmed Krylov complexity as an order parameter for quantum chaotic-integrable transitions
title_short Krylov complexity as an order parameter for quantum chaotic-integrable transitions
title_sort krylov complexity as an order parameter for quantum chaotic integrable transitions
url http://doi.org/10.1103/PhysRevResearch.7.023028
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