We review recent experimental advances in the field of efficient coupling of single atoms and light in free space. Furthermore, a comparison of efficient free space coupling and strong coupling in cavity quantum electrodynamics (QED) is given. Free space coupling does not allow for observing oscillatory exchange between the light field and the atom which is the characteristic feature of strong coupling in cavity QED. Like cavity QED, free space QED does, however, offer full switching of the light field, a 180° phase shift conditional on the presence of a single atom as well as 100% absorption probability of a single photon by a single atom. Furthermore, free space cavity QED comprises the interaction with a continuum of modes.

中文翻译：

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自由空间中的光物质相互作用

我们回顾了自由空间中单个原子和光的有效耦合领域的最新实验进展。此外，给出了腔量子电动力学（QED）中有效自由空间耦合和强耦合的比较。自由空间耦合不允许观察光场和原子之间的振荡交换，这是腔 QED 中强耦合的特征。然而，与腔 QED 一样，自由空间 QED 确实提供了光场的完全切换、180° 相移（以单个原子的存在为条件）以及单个原子对单个光子的 100% 吸收概率。此外，自由空间腔 QED 包括与连续模式的相互作用。