Nonanaliticities and ergodicity breaking in noninteracting many-body dynamics via stochastic resetting and global measurements

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Main Authors: Soldner, David, Lesanovsky, Igor, Perfetto, Gabriele
Format: Preprint
Published: 2025
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author Soldner, David
Lesanovsky, Igor
Perfetto, Gabriele
author_facet Soldner, David
Lesanovsky, Igor
Perfetto, Gabriele
contents Stochastic resetting generates nonequilibrium steady states by interspersing unitary quantum dynamics with resets at random times. When the state to which the system is reset is chosen conditionally on the outcome of a global and spatially resolved measurement, the steady state can feature collective behavior similar to what is typically observed at phase transitions. Here we investigate such conditional reset protocol in a system of noninteracting spins, where the reset state is chosen as a magnetization eigenstate, that is selected (conditioned) on the outcome of a previous magnetization measurement. The stationary states that emerge from this protocol are characterized by the density of spins in a given magnetization eigenstate, which is the analogue of the order parameter. The resulting stationary phase diagram features multiple nonanalytic points. They are of first-order type for half-integer spin, while multicritical behavior, signalled by both first and second-order discontinuities, is found for integer spin. We also show that the associated dynamics is nonergodic, i.e., which stationary state the system ultimately assumes is determined be the initial state. Interestingly, the mechanism underlying these phenomena does not rely on interactions, but the emergent nonlinear behavior is solely a consequence of correlations induced by the measurement.
format Preprint
id arxiv_https___arxiv_org_abs_2510_11450
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Nonanaliticities and ergodicity breaking in noninteracting many-body dynamics via stochastic resetting and global measurements
Soldner, David
Lesanovsky, Igor
Perfetto, Gabriele
Statistical Mechanics
Stochastic resetting generates nonequilibrium steady states by interspersing unitary quantum dynamics with resets at random times. When the state to which the system is reset is chosen conditionally on the outcome of a global and spatially resolved measurement, the steady state can feature collective behavior similar to what is typically observed at phase transitions. Here we investigate such conditional reset protocol in a system of noninteracting spins, where the reset state is chosen as a magnetization eigenstate, that is selected (conditioned) on the outcome of a previous magnetization measurement. The stationary states that emerge from this protocol are characterized by the density of spins in a given magnetization eigenstate, which is the analogue of the order parameter. The resulting stationary phase diagram features multiple nonanalytic points. They are of first-order type for half-integer spin, while multicritical behavior, signalled by both first and second-order discontinuities, is found for integer spin. We also show that the associated dynamics is nonergodic, i.e., which stationary state the system ultimately assumes is determined be the initial state. Interestingly, the mechanism underlying these phenomena does not rely on interactions, but the emergent nonlinear behavior is solely a consequence of correlations induced by the measurement.
title Nonanaliticities and ergodicity breaking in noninteracting many-body dynamics via stochastic resetting and global measurements
topic Statistical Mechanics
url https://arxiv.org/abs/2510.11450