The project is a collaboration between U of T Physics Prof. Hoi-Kwong Lo and Prof. Li Qian's group in the Department of Electrical and Computer Engineering. Dr. Zhong was a co-supervised student.

Simple Multiuser Twin-Field Quantum Key Distribution Network

Establishing secure encryption keys between any two users in a long-range communication network is important. Twin-field quantum key distribution (TFQKD), while promising for this application due to its tolerance to loss and its measurement-device-independent feature, has been limited to two users because of its requirement that phase stability of optical signals from any of the communicating user pairs be established regardless of their locations in the network. In this work, the authors demonstrate a TFQKD network by connecting three users in a Sagnac fiber ring, a configuration that provides inherent phase stability. This experiment suggests that the Sagnac TFQKD system is an effective and practical approach to implementing a long-range and secure communication network.

Read the full paper here:
https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.17.014025