Quantum simulators: from photonic to atomic

“量子模拟”领域的主要目标是：(1)通过实现可以精确调整和分析的类似系统来找到物理中棘手问题的解决方案；(2)在“模拟器”系统中观察和理解在原始系统中可能无法接近或难以理解的新现象；(3)产生与量子系统相关的新想法。由于许多这些现象都是由凝聚态物理中的问题引起的，所以模拟器系统应该用晶格来描述，并类似于固体晶格中电子的行为。我们建议在光子晶格和原子晶格中这样做。在量子模拟器的背景下，这两个系统共享许多共同的特征，即使实验设置是不同的。我们建议我们的光子和原子系统为共同的目标而工作，并探索密切相关的物理。我们小组之间的密切互动将丰富我们追求雄心勃勃的目标的能力，毫无疑问会产生新的想法。在这样做的过程中，它将使整个研究多体物理和量子模拟器的研究人员受益。我们的团队率先在光子学（耦合波导阵列）和物质波（由光引起的周期势中的超冷原子）中对晶格中的波和量子动力学进行了实验研究。从第一次观察到离散孤子和实现空间纠缠量子行走，到第一次观察到无序晶格中的安德森局域化和第一次实现光子拓扑绝缘体，光子晶格已经产生了新的物理学。超冷原子晶格在多体凝聚态问题中产生了深刻的见解，包括超流体toMott绝缘跃迁的观察，BEC-BCS交叉的实现以及具有远程相互作用的新型多体相的产生。光子系统可以表现出可能不可能实现的物理特性，例如高度可控的无序，量子效应的高度相干性，通过光学增益和损耗产生的非厄米性，以及通过环境材料的非线性产生的强相互作用。同样，物质波晶格提供了令人兴奋的可能性来研究由单粒子水平的相互作用驱动的多体物理。最近，利用单位分辨率和单原子灵敏度对光学晶格中的原子进行成像和控制也成为可能，从而为探索量子多体系统提供了全新的途径。综上所述，这些系统提供了精致的定制和灵活的平台，作为模拟器的大量晶格效应，可能是线性的，非线性的，本质上是量子的，相互作用的，和/或多体的。在这里，我们提出了一个雄心勃勃的下一代问题和挑战清单，要解决原子和光子量子模拟器。（…）

The main goals of the field of 'Quantum Simulations' are (1) to find solutions to intractable problems in physics by implementing analogous systems that can be exquisitely tuned and analyzed; (2) observe and understand novel phenomena in the 'simulator' system that may be inaccessible or poorly understood in the original, and (3) generate new ideas relevant to quantum systems. As many of these phenomena are motivated by problems in condensed matter physics, simulator systems should be described by lattices and be made analogous to the behavior of electrons in the crystal lattice of a solid. We propose to do that in photonic latticesand in lattices made of atoms. In the context of quantum simulators, these two systems share many common featires, even though the experimental settings are distinct. We propose to our photonic and atomic systems to work on common goals and explore close related physics. Close interaction between our group will enrich our ability to pursure ambitoius goals and undoubtedly lead to new ideas. In doing that, it will benefit the whole community of reserchers working on many-body physics and quantum simulators.Our groups have pioneered the experimental study of waves and quantum dynamics in lattices both in photonics (arrays of coupled waveguides) and in matter-waves (ultracold atoms in periodic potentials induced by light). Photonic lattices have given rise to new physics ranging from the first observation of discrete solitons and realization of spatially-entangled quantum walks to the first observation of Anderson localization in disordered lattices and the first realization of photonic topological insulators. Lattices of ultracold atoms yielded deep insights in many-body condensed matter problems, including the observation of the superfluid toMott insulating transition, the realization of the BEC-BCS crossover and the generation of novel many-body phases with long-range interactions. Photonic systems can exhibit physics that may be impossible to implement otherwise, such as highly controllable disorder, high degree of coherence for quantum effects, non-Hermiticity through optical gain and loss, as well as strong interactions via the nonlinearity of the ambient material. Likewise, matter waves lattices offer exciting possibilities to study many-body physics driven by interactions at the single particle level. Recently, it has also become possible to image and control atoms in optical lattices with single site resolution and single atom sensitivity, thereby offering completely new ways to explore quantum many-body systems. Taken together, these systems offer exquisitely tailorable and flexible platforms as simulators for a plethora of lattice effects that may be linear, nonlinear, intrinsically quantum, interacting, and/or many-body. Here, we propose an ambitious list of next-generation problems and challenges, to be addressed with both atomic and photonic quantum simulators. (...)