Quantum interference with independent single-photon sources over 300 km fiber
Xiang You, Mingyang Zheng, Si Chen, Runze Liu, Jian Qin, Mo-Chi Xu, Zheng-Xuan Ge, Tung-Hsun Chung, Yu-Kun Qiao, Yang-Fan Jiang, Han-Sen Zhong, Ming-Cheng Chen, Hui Wang, Yuming He, Xiu-Ping Xie, Hao Li, Lixing You, Christian Schneider, Juan Yin, Teng‐Yun Chen, Mohamed Benyoucef, Yong-Heng Huo, Sven Höfling, Qiang Zhang, Chao‐Yang Lu, Jian-Wei Pan
Abstract
In the quest to realize a scalable quantum network, semiconductor quantum dots (QDs) offer distinct advantages, including high single-photon efficiency and indistinguishability, high repetition rate (tens of gigahertz with Purcell enhancement), interconnectivity with spin qubits, and a scalable on-chip platform. However, in the past two decades, the visibility of quantum interference between independent QDs rarely went beyond the classical limit of 50%, and the distances were limited from a few meters to kilometers. Here, we report quantum interference between two single photons from independent QDs separated by a 302 km optical fiber. The single photons are generated from resonantly driven single QDs deterministically coupled to microcavities. Quantum frequency conversions are used to eliminate the QD inhomogeneity and shift the emission wavelength to the telecommunication band. The observed interference visibility is 0.67 ± 0.02 (0.93 ± 0.04) without (with) temporal filtering. Feasible improvements can further extend the distance to ∼600 km. Our work represents a key step to long-distance solid-state quantum networks.