Non-equilibrium critical scaling and universality in a quantum simulator
Non-equilibrium critical scaling and universality in a quantum simulator
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发表时间：
2023-09
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通讯作者：
A. De;P. Cook;K. Collins;W. Morong;D. Paz;P. Titum;G. Pagano;A. V. Gorshkov;M. Maghrebi;C. Monroe
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作者：
A. De;P. Cook;K. Collins;W. Morong;D. Paz;P. Titum;G. Pagano;A. V. Gorshkov;M. Maghrebi;C. Monroe
普适性和标度定律是平衡相变和临界现象的标志。然而，将这些概念扩展到非平衡系统是一个突出的挑战。尽管动态相的研究近年来取得了一些进展，但人们对非平衡态现象的普适性和标度规律的了解远远少于平衡态现象。在这项工作中，我们使用具有单离子分辨率的捕获离子量子模拟器，研究了量子猝灭到临界点后临界波动的非平衡性质。我们探讨了一系列猝灭后自旋涨落的尺度到一个长程伊辛模型的临界哈密顿量。对于多达50个自旋的系统，我们证明了猝灭后波动的幅度和时间标度随系统大小的变化具有不同的通用临界指数。虽然一般淬火可以导致热临界行为，但我们发现从一个临界状态到另一个临界状态的第二次淬火（即双重淬火）会导致没有平衡对应的临界行为。我们的结果证明了量子模拟器探索超越平衡范式的普遍尺度的能力。
Universality and scaling laws are hallmarks of equilibrium phase transitions and critical phenomena. However, extending these concepts to non-equilibrium systems is an outstanding challenge. Despite recent progress in the study of dynamical phases, the universality classes and scaling laws for non-equilibrium phenomena are far less understood than those in equilibrium. In this work, using a trapped-ion quantum simulator with single-ion resolution, we investigate the non-equilibrium nature of critical fluctuations following a quantum quench to the critical point. We probe the scaling of spin fluctuations after a series of quenches to the critical Hamiltonian of a long-range Ising model. With systems of up to 50 spins, we show that the amplitude and timescale of the post-quench fluctuations scale with system size with distinct universal critical exponents. While a generic quench can lead to thermal critical behaviour, we find that a second quench from one critical state to another (i.e. a double quench) results in critical behaviour that does not have an equilibrium counterpart. Our results demonstrate the ability of quantum simulators to explore universal scaling beyond the equilibrium paradigm.