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arXiv · 2309.10856

Non-equilibrium critical scaling and universality in a quantum simulator

Arinjoy De·Patrick Cook·Mostafa Ali·Kate Collins·William Morong·Daniel Paz·Paraj Titum·Guido Pagano·Alexey V. Gorshkov·Mohammad Maghrebi·CHristopher Monroe
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Abstract

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-spin 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, depending on the quench protocol. While a generic quench can lead to thermal critical behavior, we find that a second quench from one critical state to another (i.e.~a double quench) results in a new universal non-equilibrium behavior, identified by a set of critical exponents distinct from their equilibrium counterparts. Our results demonstrate the ability of quantum simulators to explore universal scaling beyond equilibrium.

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Arinjoy De, Patrick Cook, Mostafa Ali, Kate Collins, William Morong, Daniel Paz, Paraj Titum, Guido Pagano, Alexey V. Gorshkov, Mohammad Maghrebi, CHristopher Monroe. 2023-09-19. Non-equilibrium critical scaling and universality in a quantum simulator. https://doi.org/10.1038/s41467-025-63398-y

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