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arXiv:2610.25310

Anomalously fast heating of ground states in dephased $SU(N)$ spin systems

Tairan Lou, Junxiao Chen, Xiang-Ping Jiang, Mingdi Xu, Lei Pan

quant-phSubmitted Oct 18, 2026• Announced Oct 20, 2026• 0 citations
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Abstract

We identify a strong quantum Mpemba effect in which a many-body ground state heats faster than every Gibbs state at finite positive temperature under the same dissipative dynamics within a fixed-color sector. In ferromagnetic $SU(N)$ exchange systems with local dephasing, exact coherence shells confine the ground-state evolution and exclude all slower Liouvillian modes. Its relaxation rate is fixed by the bath, independently of system size, exchange graph, and integrability. We derive an energy-resolved sign criterion that guarantees a slower thermal contribution throughout the positive-temperature range. An exact finite-chain solution proves this rate inversion, and symmetry-resolved calculations confirm the criterion in larger spin-one chains, including nonintegrable exchange. The zero-temperature endpoint of a continuous Gibbs family can therefore be dynamically isolated by its exact exclusion from slow relaxation channels.

Comments
20 pages, 8 figures; includes appendices

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Anomalously fast heating of ground states in dephased SU(N)SU(N)SU(N) spin systems
We identify a strong quantum Mpemba effect in which a many-body ground state heats faster than every Gibbs state at finite positive temperature under the same dissipative dynamics within a fixed-color sector. In ferromagnetic SU(N)SU(N)SU(N) exchange systems with local dephasing, exact coherence shells confine the ground-state evolution and exclude all slower Liouvillian modes. Its relaxation rate is fixed by the bath, independently of system size, exchange graph, and integrability. We derive an energy-resolved sign criterion that guarantees a slower thermal contribution throughout the positive-temperature range. An exact finite-chain solution proves this rate inversion, and symmetry-resolved calculations confirm the criterion in larger spin-one chains, including nonintegrable exchange. The zero-temperature endpoint of a continuous Gibbs family can therefore be dynamically isolated by its exact exclusion from slow relaxation channels.
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The Unruh effect links acceleration to thermalization, providing a relativistic setting for anomalous quantum relaxation. We demonstrate a {\it relativistic} strong quantum Mpemba effect in the Unruh thermalization of a two-level detector coupled to a massless scalar field. For a fixed pair of isospectral initial states, relaxation curves that never cross in inertial motion exhibit a Mpemba crossing above a threshold acceleration. At a higher, precisely tuned acceleration, the initially farther state has zero overlap with the slowest decay mode and relaxes with a faster asymptotic exponential rate. We identify how competition between transition and dephasing channels governs the relaxation spectrum, where sufficiently strong longitudinal coupling enables acceleration to switch the relaxation bottleneck between population and coherence modes. We derive the spectral-switching condition and construct isospectral preparation protocols that eliminate slow-mode contributions within their physical domains. Our results establish acceleration as a control parameter for anomalous quantum relaxation, connecting relativistic quantum dynamics with nonequilibrium thermodynamics.
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Collective coupling to the Minkowski vacuum allows uniformly accelerated quantum detectors to exhibit a strong quantum Mpemba effect, in which a state initially farther from equilibrium relaxes faster than a closer one. We establish the existence of this effect for every fixed finite number of detectors N≥2N\geq 2N≥2 at sufficiently small transverse separation within the pointlike secular master equation. The mechanism originates from two reflection sectors whose populations are conserved by the leading collective dynamics. Weak intersector transfer at finite separation generates an isolated, parametrically slow relaxation mode. A simple family of initial states permits its leading-order cancellation by matching the equilibrium sector populations, while a corrected preparation eliminates the slow-mode amplitude exactly. We construct a reference state that establishes a genuine reversal of trace-distance ordering. Numerical calculations and local-rate-preserving controls identify the collective origin of the effect, while spatially smeared detector calculations support its persistence within the second-order secular framework. The same mechanism extends to detectors coupled to a common thermal field, with analytically distinct slow relaxation rates. Thus, strong Mpemba relaxation is not exclusive to acceleration but emerges from a more general interplay between collective dissipation, reflection-sector conservation, and weak symmetry-breaking transfer.
We investigate how nonequilibrium quantum initial states can reduce the finite-time thermodynamic cost of Landauer erasure. Considering a general finite-dimensional quantum memory coupled to a thermal reservoir via a Davies generator, we show that the dissipated heat at a fixed operational erasure fidelity is largely controlled by the overlap of the initial state with the slowest Liouvillian relaxation mode. We derive a modified finite-time Landauer bound in which the excess dissipation above the quasistatic limit scales quadratically with this slow mode projection, and we prove a sufficient Mpemba Landauer condition under which a hotter state can erase faster and dissipate less heat than a colder preparation, without violating Landauer's principle. A minimal qutrit model illustrates these quantum Mpemba speedups and reveals broad parameter regimes where coherence and Hamiltonian-induced modes conspire to suppress finite-time entropy production. We further identify practical control knobs, including temperature tuning, coherence engineering, and Hamiltonian shaping of Liouvillian spectra, which enable Mpemba-enhanced erasure to be directly tested on platforms such as superconducting circuits, trapped ions, semiconductor quantum dots, and solid-state spins.