Two-photon interference between independent atomic and quantum dot single-photon sources for hybrid quantum network.

Abstract

Hybrid quantum systems play a crucial role in advancing scalable and versatile quantum networks as they combine the strengths of different quantum platforms. An important challenge for the development of hybrid quantum networks lies in interfacing heterogeneous quantum nodes and distributing entanglement among them. Single photons emitted from these dissimilar quantum nodes typically show distinct spectral and temporal properties. Therefore, they necessitate emitters' spectral modification and temporal synchronization, which introduce significant photon losses and require additional resources. In this work, we successfully generate indistinguishable photons from two distinct quantum systems: a warm atomic ensemble and a solid-state quantum dot. Remarkably, two-photon interference between dissimilar sources is achieved without additional spectral modification of single photons under continuous-wave operation and time-resolved coincidence detection, providing a practical route toward hybrid quantum nodes. A 133Cs atomic ensemble can efficiently generate heralded single photons at the wavelength of 917 nm of the 6 P 3 / 2 - 6 D 5 / 2 transition, while the single photons emitted from an InAs/GaAs quantum dot can be tuned to match the 133Cs transition wavelength. Our dense warm atomic ensemble and cavity-coupled quantum dot can efficiently generate bright and resonant single photons at detection rates approaching the MHz range, respectively. More importantly, these single photons exhibit inherent spectral similarity not only in the wavelength but also in the spectral linewidth, achieving a high spectral overlap of 0.88 . Such intrinsic compatibility between dissimilar quantum sources is essential to leverage the advantages of different quantum platforms, paving the way toward a large-scale and functional hybrid quantum network.