Single photon sources, which are compatible with quantum memories are an important component of quantum networks. In this article, we show optical investigations on isolated GaAs/Al$_{0.25}$Ga$_{0.75}$As quantum dots grown via droplet epitaxy, which emit single photons on resonance with the Rb-87-D$_2$ line (780 nm). Under continuous wave resonant excitation conditions, we observe bright, clean and narrowband resonance fluorescence emission from such a droplet quantum dot. Furthermore, the second-order correlation measurement clearly demonstrates the single photon emission from this resonantly driven transition. Spectrally resolved resonance fluorescence of a similar quantum dot yields a linewidth as narrow as 660 MHz ($ 2.7~\mu eV $), which corresponds to a coherence time of 0.482 ns. The observed linewidth is the smallest reported so far for strain free GaAs quantum dots grown via the droplet method. We believe that this single photon source can be a prime candidate for applications in optical quantum networks.

中文翻译：

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基于 GaAs 液滴量子点的原子量子存储器兼容单光子源的共振荧光

与量子存储器兼容的单光子源是量子网络的重要组成部分。在本文中，我们展示了对通过液滴外延生长的孤立 GaAs/Al$_{0.25}$Ga$_{0.75}$As 量子点的光学研究，这些量子点在与 Rb-87-D$_2$ 共振时发射单光子线（780 纳米）。在连续波共振激发条件下，我们观察到这种液滴量子点发出明亮、干净和窄带的共振荧光。此外，二阶相关测量清楚地证明了这种共振驱动跃迁的单光子发射。类似量子点的光谱分辨共振荧光产生窄至 660 MHz ($ 2.7~\mu eV $) 的线宽，对应于 0.482 ns 的相干时间。观察到的线宽是迄今为止通过液滴法生长的无应变 GaAs 量子点所报道的最小线宽。我们相信这种单光子源可以成为光量子网络应用的主要候选者。