Researchers constructed a large-scale, fully connected quantum network capable of maintaining user-to-user security over a distance of 200 kilometers, according to a report published in Nature Communications. The system allows every user on the network to connect simultaneously to every other user, establishing a versatile networking architecture that operates securely even when passing through an untrusted network provider.
The architecture is built on two-photon Hong-Ou-Mandel interference. To address scalability challenges that previously hindered practical applications of fully connected networks, the team integrated soliton microcomb technology with photonic encoding chips. This combination allowed the researchers to demonstrate precise, massively parallel frequency generation and locking across the network.
Using these integrated chips, the team achieved high-visibility Hong-Ou-Mandel interference and carried out measurement-device-independent quantum key distribution. The resulting setup offers strict information-theoretic security across metropolitan and intercity distances, creating a foundation for scaling multi-user quantum communications without relying on trusted central nodes or operators.
The project involved researchers from the Laboratory of Quantum Information at the University of Science and Technology of China (USTC) in Hefei, the Xi’an Institute of Optics and Precision Mechanics of the Chinese Academy of Sciences, and the National University of Defense Technology in Changsha. Equal contributions to the study were made by Fang-Xiang Wang, Sheng-Teng Zheng, Long Huang, and Guo-Wei Zhang.
The paper was received on May 15, 2026, accepted on July 3, 2026, and published on August 3, 2026. Microchip fabrication was supported by the USTC Center for Micro and Nanoscale Research and Fabrication. Research funding came from the National Natural Science Foundation of China, the Quantum Science and Technology-National Science and Technology Major Project, and the CAS Project for Young Scientists in Basic Research.
