The highly complicated nature of far from equilibrium systems can lead to a complete breakdown of the physical intuition developed in equilibrium. A famous example of this is the Mpemba effect, which states that nonequilibrium states may relax faster when they are further from equilibrium or, put another way, hot water can freeze faster than warm water. Despite possessing a storied history, the precise criteria and mechanisms underpinning this phenomenon are still not known. Here, we study a quantum version of the Mpemba effect that takes place in closed many-body systems with a $U(1)$ conserved charge: in certain cases a more asymmetric initial configuration relaxes and restores the symmetry faster than a more symmetric one. In contrast to the classical case, we establish the criteria for this to occur in arbitrary integrable quantum systems using the recently introduced entanglement asymmetry. We describe the quantum Mpemba effect in such systems and relate the properties of the initial state, specifically its charge fluctuations, to the criteria for its occurrence. These criteria are expounded using exact analytic and numerical techniques in several examples, a free fermion model, the Rule 54 cellular automaton, and the Lieb-Liniger model.

中文翻译：

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可积系统中量子姆潘巴效应的微观起源


远离平衡系统的高度复杂性可能导致平衡状态下发展的物理直觉的彻底崩溃。一个著名的例子是姆潘巴效应，它指出，当非平衡状态远离平衡状态时，它们可能会松弛得更快，或者换句话说，热水比温水结冰的速度更快。尽管拥有传奇的历史，但支撑这种现象的精确标准和机制仍然未知。在这里，我们研究了 Mpemba 效应的量子版本，该效应发生在具有 $U(1)$ 守恒电荷的封闭多体系统中：在某些情况下，更不对称的初始配置比更对称的初始配置更快地松弛和恢复对称性。一。与经典情况相反，我们使用最近引入的纠缠不对称性建立了在任意可积量子系统中发生这种情况的标准。我们描述了此类系统中的量子姆彭巴效应，并将初始状态的特性（特别是其电荷波动）与其发生的标准联系起来。这些标准通过几个例子、自由费米子模型、规则 54 元胞自动机和 Lieb-Liniger 模型中的精确分析和数值技术进行了阐述。