Quantum Mpemba effect in subsystem gauge symmetry restoration
Phys. Rev. B 113, 214311 – Published 10 June, 2026
DOI: https://doi.org/10.1103/b7ls-215n
Abstract
Understanding relaxation in isolated quantum many-body systems remains a central challenge. Recently, the quantum Mpemba effect (QME)—a counterintuitive relaxation phenomenon—has attracted considerable attention and has been extensively studied in systems with global symmetries. Here, we study the QME in gauge theories with massive local gauge symmetries. In the lattice Schwinger model, we demonstrate that the gauge structure of the reduced density matrix of a subsystem is entirely determined by the initial state and remains unchanged during the time evolution. We then investigate whether subsystem gauge symmetry can be dynamically restored following a symmetric quench. Analytical and numerical results show that, when the Maxwell term is zero, subsystem gauge-symmetry restoration fails due to an emergent conservation law. However, for any finite Maxwell term, subsystem gauge symmetry is restored in the thermodynamic limit. Based on these results, we systematically construct a families of initial states exhibiting the QME. We further explore the QME in the quantum link model, a truncated lattice Schwinger model, which has been realized in experiments. Moreover, we propose an experimentally accessible order parameter that correctly captures the QME. Our work demonstrates the generality of the quantum Mpemba effect even in the local gauge symmetries, and is directly relevant to ongoing quantum-simulation experiments of gauge theories.
