Hybrid systems of laser-cooled trapped ions and ultracold atoms combined in a single experimental setup have recently emerged as a new platform for fundamental research in quantum physics. This paper reviews the theoretical and experimental progress in research on cold hybrid ion-atom systems which aim to combine the best features of the two well-established fields. A broad overview is provided of the theoretical description of ion-atom mixtures and their applications, and a report is given on advances in experiments with ions trapped in Paul or dipole traps overlapped with a cloud of cold atoms, and with ions directly produced in a Bose-Einstein condensate. This review begins with microscopic models describing the electronic structure, interactions, and collisional physics of ion-atom systems at low and ultralow temperatures, including radiative and nonradiative charge-transfer processes and their control with magnetically tunable Feshbach resonances. Then the relevant experimental techniques and the intrinsic properties of hybrid systems are described. In particular, the impact is discussed of the micromotion of ions in Paul traps on ion-atom hybrid systems. Next, a review of recent proposals is given for using ions immersed in ultracold gases for studying cold collisions, chemistry, many-body physics, quantum simulation, and quantum computation and their experimental realizations. The last part focuses on the formation of molecular ions via spontaneous radiative association, photoassociation, magnetoassociation, and sympathetic cooling. Applications and prospects are discussed of cold molecular ions for cold controlled chemistry and precision spectroscopy.

中文翻译：

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冷杂离子原子系统

在单个实验装置中结合使用激光冷却的捕获离子和超冷原子的混合系统，最近已经成为量子物理学基础研究的新平台。本文回顾了冷杂化离子原子系统研究的理论和实验进展，该系统旨在结合两个成熟领域的最佳特征。提供了对离子-原子混合物及其应用的理论描述的广泛概述，并给出了有关在Paul中捕获的离子或与冷原子云重叠的偶极阱中捕获的离子以及在原子中直接产生的离子的实验进展的报告。玻色-爱因斯坦冷凝物。这篇评论从微观模型开始，描述了低温和超低温条件下离子原子系统的电子结构，相互作用和碰撞物理学，包括辐射和非辐射电荷转移过程，以及通过磁可调Feshbach共振进行控制。然后描述了相关的实验技术和混合系统的内在特性。特别是，讨论了Paul阱中离子的微运动对离子-原子混合系统的影响。接下来，对最近的建议进行了综述，该建议使用浸入超冷气体中的离子来研究冷碰撞，化学，多体物理学，量子模拟和量子计算及其实验实现。最后一部分重点介绍通过自发辐射缔合，光缔合，磁缔合和交感冷却形成分子离子的过程。讨论了用于冷控制化学和精密光谱学的冷分子离子的应用和前景。