Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, I-20133 Milano, Italy & IFISC (UIB-CSIC), Instituto de Fisica Interdisciplinar y Sistemas Complejos – Palma de Mallorca, Spain
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Abstract
The behavior of systems far from equilibrium is often complex and unpredictable, challenging and sometimes overturning the physical intuition derived from equilibrium scenarios. One striking example of this is the Mpemba effect, which implies that non-equilibrium states can sometimes relax more rapidly when they are further from equilibrium. Despite a rich historical background, the precise conditions and mechanisms behind this phenomenon remain unclear. Recently, there has been growing interest in investigating accelerated relaxation and Mpemba-like effects within quantum systems. In this work, we explore a quantum manifestation of the Mpemba effect in a simple and paradigmatic model of open quantum systems: the damped quantum harmonic oscillator, which describes the relaxation of a bosonic mode in contact with a thermal bath at finite temperature $T$. By means of an exact analytical analysis of the relaxation dynamics based on the method of moments in both population and coherence subspaces, we demonstrate that any initial distribution of populations with the first $r$ moments exactly matching those of the equilibrium distribution shows a super-accelerated relaxation to equilibrium at a rate linearly increasing with $r$, leading to a pronounced Mpemba effect. In particular, one can find a broad class of far-from-equilibrium distributions that relax to equilibrium faster than any other initial thermal state with a temperature $T’$ arbitrarily close to $T$. The super-accelerated relaxation effect is shown to persist even for a broad class of initial states with non-vanishing coherences, and a general criterion for the observation of super-accelerated thermalization is presented.

Featured image: Cartoon of the Mpemba effect. A system far from equilibrium can relax to equilibrium more quickly than those closer to it.
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Cited by
[1] Filiberto Ares, Pasquale Calabrese, and Sara Murciano, “The quantum Mpemba effects”, arXiv:2502.08087, (2025).
[2] Doruk Can Alyürük, Mahir H. Yeşiller, Vlatko Vedral, and Onur Pusuluk, “Thermodynamic limits of the Mpemba effect: A unified resource theory analysis”, arXiv:2502.00123, (2025).
[3] Gianluca Teza, John Bechhoefer, Antonio Lasanta, Oren Raz, and Marija Vucelja, “Speedups in nonequilibrium thermal relaxation: Mpemba and related effects”, arXiv:2502.01758, (2025).
[4] Stefano Longhi, “Laser Mpemba effect”, Optics Letters 50 6, 2069 (2025).
[5] Ivan Medina, Oisín Culhane, Felix C. Binder, Gabriel T. Landi, and John Goold, “Anomalous discharging of quantum batteries: the ergotropic Mpemba effect”, arXiv:2412.13259, (2024).
The above citations are from SAO/NASA ADS (last updated successfully 2025-03-26 14:37:29). The list may be incomplete as not all publishers provide suitable and complete citation data.
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