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arXiv:2607.17975

Strong Quantum Mpemba Effect from Exact Slow-Mode Selection in Constrained Rydberg Chains

Mingdi Xu, Kaixiang Lu, Zijun Wei, Xiang-Ping Jiang, Haiping Hu, Lei Pan

quant-phcond-mat.quant-gascond-mat.str-elSubmitted Jul 20, 2026• Announced Jul 21, 2026• 0 citations• Revised Aug 4, 2026 (v2)
v1 · Jul 20, 2026v2 · Aug 4, 2026
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Abstract

CStrong quantum Mpemba acceleration requires suppressing the slowest visible Liouvillian relaxation channel, but a robust many-body mechanism for enforcing such suppression remains challenging. We identify such a mechanism in locally dephased constrained Rydberg chains through exact slow-mode selection. For constrained single-spin-flip Hamiltonians, local dephasing turns the Hamiltonian itself into an exact left Liouvillian eigenmode, $\mathcal L^\dagger(H)=-γH$. A finite-temperature reference state generically overlaps with this $H$-like slow mode, whereas translationally invariant states with $\mathrm{Tr}(Hρ_0)=0$ remove it and are confined to the $Q=0$ operator sector. When the next visible $Q=0$ mode decays faster, these selected states exhibit a strong quantum Mpemba effect. We demonstrate this mechanism in the PXP chain for a zero-energy scar eigenstate, the all-zero product state, and a translation-invariant $Z_2$ cat state, and show that it persists in the $(2,3)$ model and the longer-range blockade family. Our results identify Liouvillian mode visibility, rather than special scar wave functions, as the organizing principle for anomalously fast relaxation in constrained open quantum systems.

Comments
8+13 pages, 4 figures, comments are welcome

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We uncover a symmetry-filtered mechanism for anomalous dissipative relaxation in a long-range XXZ spin chain subject to local dephasing. At the isotropic point, the coherent Hamiltonian has global SU(2)SU(2)SU(2) symmetry, whereas the full Liouvillian retains only the U(1)U(1)U(1) symmetry associated with total magnetization. This structure pins a family of spatially uniform zero-U(1)U(1)U(1)-charge left eigenoperators with exact eigenvalues λ=−2qλ=-2qλ=−2q, forming a Liouvillian relaxation comb. For the ferromagnetic Dicke ground state, the overlap envelope on this comb is known exactly at finite size and becomes Gaussian in the large-SSS limit. Since higher-qqq components decay rapidly, the q=1q=1q=1 comb tooth controls the long-time dynamics and yields universal D(t)∼e−2tD(t)\sim e^{-2t}D(t)∼e−2t relaxation independent of system size and interaction range. This mode-accessibility filtering realizes a spectral strong quantum Mpemba effect: an initially farther state relaxes faster than closer thermal states because slow non-steady Liouvillian modes are inaccessible. Weak breaking of the Hamiltonian SU(2)SU(2)SU(2) symmetry restores slow-mode overlap and suppresses this acceleration.
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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.