Understanding the dynamics of strongly interacting disordered quantum systems is one of the most challenging problems in modern science, due to features such as the breakdown of thermalization and the emergence of glassy phases of matter. We report on the observation of anomalous relaxation dynamics in an isolated XXZ quantum spin system realized by an ultracold gas of atoms initially prepared in a superposition of two different Rydberg states. The total magnetization is found to exhibit subexponential relaxation analogous to classical glassy dynamics, but in the quantum case this relaxation originates from the buildup of nonclassical correlations. In both experiment and semiclassical simulations, we find the evolution toward a randomized state is independent of the strength of disorder up to a critical value. This hints toward a unifying description of relaxation dynamics in disordered isolated quantum systems, analogous to the generalization of statistical mechanics to out-of-equilibrium scenarios in classical spin glasses.

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无序海森堡量子自旋系统中的玻态动力学

由于诸如热分解和物质玻璃相的出现等特征，了解强相互作用的无序量子系统的动力学是现代科学中最具挑战性的问题之一。我们报告了在一个隔离的XXZ量子自旋系统中的异常弛豫动力学的观察结果，该系统由最初在两个不同的里德堡态的叠加中制备的原子的超冷气体实现。发现总磁化强度表现出类似于经典玻璃态动力学的次指数弛豫，但是在量子情况下，这种弛豫源自非经典相关性的建立。在实验和半经典模拟中，我们都发现向随机状态的演变与无序强度无关，直到临界值为止。