Quantum key distribution (QKD) promises unconditionally information-theoretic secure communication guaranteed by the laws of physics and has become one of the most crucial candidates in future security aspects. Developing a large-scale network with a scalable and integrated scheme is of great significance for expanding the advantages of QKD protocols among multiple users.

Here, we propose a sixteen-user fully connected quantum network by using a novel time-bin entangled source implemented in the integrated multi-channel periodically poled lithium niobate waveguides. Based on this entangled source, the quantum processor prepares 120 entangled photon pairs to allocate 15 links to each user by utilizing dense wavelength division multiplexing technology. To enable the users’ communication with each other simultaneously, we develop a phase-compensated Mach-Zehnder Interferometer based on a Fourier-transform setup to control the relative phase of the interferometer for all the involved wavelength channels. The experimental results show that the network can support sixteen users for long-distance communication with each other simultaneously. Our time-bin entangled network promises a new potential for constructing large-scale and extensible quantum networks with an integrated photonic architecture.

We thank Dr. Youqi Nie and Dr. Qi Xu from the University of Science and Technology of China and Dr. Juan Feng from Shanghai Jiao Tong University for their assistance in this work.

Figure 1. Conceptual illustration of the fully connected network architecture. a) Structure of the physical topology of the network. b) Structure of the communication topology of the network.

Figure 2. Experimental results between Alice and all other users.

This work is published in“Yiwen Huang, Zhantong Qi, Yilin Yang, Yuting Zhang, Yuanhua Li, Yuanlin Zheng, and Xianfeng Chen, A Sixteen-user Time-bin Entangled Quantum Communication Network with Fully Connected Topology, Laser & Photonics Reviews, 2301026 (2024)”。

Link：https://onlinelibrary.wiley.com/doi/full/10.1002/lpor.202301026