Transitions of the Lyapunov spectrum and entanglement entropy in monitored quantum dynamics with homogeneous unitary gates

Fuente: arXiv
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Autores principales: Mochizuki, Ken, Hamazaki, Ryusuke
Formato: Preprint
Publicado: 2025
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author Mochizuki, Ken
Hamazaki, Ryusuke
author_facet Mochizuki, Ken
Hamazaki, Ryusuke
contents We explore the Lyapunov spectrum and entanglement entropy in systems evolved by quantum measurements and spatially homogeneous unitary gates. In models with temporally random and Floquet unitary gates, we find that the Lyapunov exponents typically converge to values independent of measurement outcomes and that spectral transitions of the Lyapunov spectrum and entanglement transitions of ground states occur at the same measurement thresholds. Our results indicate that (i) randomness due to quantum measurements is enough, or equivalently, randomness of unitary gates is not essential, for the typical convergence of the Lyapunov spectrum and that (ii) the correspondence between the spectral transition and entanglement transition is ubiquitous in a wide range of systems. We also discuss why the typical convergence occurs, in light of the uniqueness and positive definiteness of stationary states in the completely-positive trace-preserving (CPTP) dynamics averaged over random measurement outcomes.
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id arxiv_https___arxiv_org_abs_2503_20217
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Transitions of the Lyapunov spectrum and entanglement entropy in monitored quantum dynamics with homogeneous unitary gates
Mochizuki, Ken
Hamazaki, Ryusuke
Quantum Physics
Statistical Mechanics
We explore the Lyapunov spectrum and entanglement entropy in systems evolved by quantum measurements and spatially homogeneous unitary gates. In models with temporally random and Floquet unitary gates, we find that the Lyapunov exponents typically converge to values independent of measurement outcomes and that spectral transitions of the Lyapunov spectrum and entanglement transitions of ground states occur at the same measurement thresholds. Our results indicate that (i) randomness due to quantum measurements is enough, or equivalently, randomness of unitary gates is not essential, for the typical convergence of the Lyapunov spectrum and that (ii) the correspondence between the spectral transition and entanglement transition is ubiquitous in a wide range of systems. We also discuss why the typical convergence occurs, in light of the uniqueness and positive definiteness of stationary states in the completely-positive trace-preserving (CPTP) dynamics averaged over random measurement outcomes.
title Transitions of the Lyapunov spectrum and entanglement entropy in monitored quantum dynamics with homogeneous unitary gates
topic Quantum Physics
Statistical Mechanics
url https://arxiv.org/abs/2503.20217