Non-equilibrium phenomena in Rydberg lattice gases with facilitation constraints.

对远离平衡态的量子多体系统的探索是物理学中的一个热门课题。在我们的项目中，我们的目标是探索这一广泛领域的新方面，特别是我们将探索玻璃形成系统基础物理过程的量子类似物。我们建立在最近建立的里德伯原子相互作用的晶格气体之间的联系-这是高度激发态的原子-和玻璃形成物的软物质模型的物理学。后者是具有所谓动力学约束的自旋系统，它模拟了过冷液体中的排除体积效应，并使弛豫动力学具有强烈的集体性和缓慢性。在里德伯气体中，由于强烈的原子间相互作用，动力学约束自然出现。在我们的建议中，我们将重点关注所谓的易化约束，即在受激里德伯原子附近激发概率增强。这种机制类似于典型的经典玻璃形成模型，如Fredrickson-Anderson自旋模型，该模型也具有条件激发动力学，即一个自旋只有在邻近的自旋被激发时才会翻转。这些经典模型系统显示出玻璃钢的标志性特征，如动力学非均质性和超慢弛豫。里德伯原子提供了独特的优势，在量子领域扩展和探索这些动态现象，促进自旋翻转是完全相干的。由于几乎没有任何实验，而且最先进的数值技术很快就达到了适用的极限，因此对这一制度知之甚少。这在涉及长时间和高维的情况下尤其如此。拟议项目的目标是开展一个相互关联的实验理论研究计划，揭示在易化约束存在下晶格自旋气体的相关量子动力学。为此，我们将扩大现有的实验平台，以便在长时间内观察和表征一维和二维系统中的里德伯晶格气体。此外，我们将开发理论模型和数值方法来理解与实验密切相关的多体动力学，这将使我们能够仔细检查和验证近似。我们期望我们的项目将在很大程度上未被探索的量子体系中揭示非平衡现象，包括亚稳态、遍历性破缺以及玻璃性的出现。我们的研究将为长时间实验控制和监测多体量子系统提供新的方法，我们将提供新的理论方法，并在冷原子物理和软物质系统物理之间建立联系。

The exploration of quantum many-body systems far from equilibrium is a topical subject area in physics. In our project we aim to explore new aspects of this wide field, and in particular we will explore quantum analogues of fundamental physical processes underlying glass forming systems. We build on a recently established connection between lattice gases of interacting Rydberg atoms – which are atoms in highly excited states – and the physics of soft-matter models of glass formers. The latter are spin systems with so-called kinetic constraints that mimic excluded volume effects in supercooled liquids and make the relaxation dynamics strongly collective and slow. In Rydberg gases kinetic constraints emerge naturally as a consequence of the strong interatomic interactions. The situation we will focus on in our proposal concerns the so-called facilitation constraint where the excitation probability is enhanced in the vicinity of an excited Rydberg atom. This mechanism is akin to canonical classical glass forming models, such as the Fredrickson-Anderson spin model, which also features such conditional excitation dynamics, i.e. a spin is only flipped if a neighbouring spin is excited. These classical model systems display hallmark features of glassines, such as dynamical heterogeneity as well as ultra-slow relaxation. Rydberg atoms offer the unique advantage to extend and explore these dynamical phenomena in the quantum domain where facilitated spin flips are fully coherent. Very little is known about this regime, as there exist hardly any experiments and state-of-the-art numerical techniques quickly reach their limit of applicability. This is particularly the case when long times and higher dimensions are involved.The goal of the proposed project is to conduct an interlinked experiment-theory research programme that sheds light on the correlated quantum dynamics of lattice spin gases in the presence of facilitation constraints. To this end we will augment an existing experimental platform to allow for the observation and characterisation of Rydberg lattice gases in one- and two-dimensional systems over long times. Furthermore, we will develop theoretical models and numerical approaches to understand the correlated many-body dynamics in close connection to the experiment which will allow us to scrutinise and validate approximations. We expect that our project will shed new light on non-equilibrium phenomena, including metastability, ergodicity breaking as well as the emergence of glassiness, in the largely unexplored quantum regime. Our research will deliver new approaches to experimentally control and monitor many-body quantum systems over long times, we will deliver new theoretical methods and establish a link between cold atomic physics and the physics of soft-matter systems.