Versatile interfaces with strong and tunable light–matter interactions are essential for quantum science1 because they enable mapping of quantum properties between light and matter1. Recent studies2–10 have proposed a method of controlling light–matter interactions using the rich interplay of photon-mediated dipole–dipole interactions in structured subwavelength arrays of quantum emitters. However, a key aspect of this approach—the cooperative enhancement of the light–matter coupling strength and the directional mirror reflection of the incoming light using an array of quantum emitters—has not yet been experimentally demonstrated. Here we report the direct observation of the cooperative subradiant response of a two-dimensional square array of atoms in an optical lattice. We observe a spectral narrowing of the collective atomic response well below the quantum-limited decay of individual atoms into free space. Through spatially resolved spectroscopic measurements, we show that the array acts as an efficient mirror formed by a single monolayer of a few hundred atoms. By tuning the atom density in the array and changing the ordering of the particles, we are able to control the cooperative response of the array and elucidate the effect of the interplay of spatial order and dipolar interactions on the collective properties of the ensemble. Bloch oscillations of the atoms outside the array enable us to dynamically control the reflectivity of the atomic mirror. Our work demonstrates efficient optical metamaterial engineering based on structured ensembles of atoms4,8,9 and paves the way towards controlling many-body physics with light5,6,11 and light–matter interfaces at the single-quantum level7,10. A single two-dimensional array of atoms trapped in an optical lattice shows a tunable cooperative subradiant optical response, acting as a single-monolayer optical mirror with controllable reflectivity.

中文翻译：

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由单个结构化原子层形成的亚辐射光学镜

具有强且可调谐的光-物质相互作用的多功能界面对于量子科学 1 至关重要，因为它们能够映射光和物质之间的量子特性 1。最近的研究 2-10 提出了一种控制光物质相互作用的方法，该方法利用量子发射器的结构化亚波长阵列中光子介导的偶极-偶极相互作用的丰富相互作用。然而，这种方法的一个关键方面 - 使用量子发射器阵列协同增强光 - 物质耦合强度和入射光的定向镜面反射 - 尚未通过实验证明。在这里，我们报告了对光学晶格中二维原子方形阵列的协同子辐射响应的直接观察。我们观察到集体原子响应的光谱变窄，远低于单个原子进入自由空间的量子限制衰变。通过空间分辨光谱测量，我们表明该阵列充当由数百个原子的单个单层形成的有效镜子。通过调整阵列中的原子密度和改变粒子的排序，我们能够控制阵列的协同响应，并阐明空间有序和偶极相互作用的相互作用对整体集体特性的影响。阵列外原子的布洛赫振荡使我们能够动态控制原子镜的反射率。我们的工作展示了基于原子结构集合的高效光学超材料工程4,8, 9 并为使用光 5、6、11 和单量子水平 7、10 的光物质界面控制多体物理铺平了道路。被困在光学晶格中的单个二维原子阵列显示出可调谐的协同子辐射光学响应，充当具有可控反射率的单层光学镜。