The network covers a distance of 4,600 kilometers (about 2850 miles) and includes both ground based fiber as well as satellite links. The fiber portion covers a route that goes from Shanghai to Heifei to Jinan to Beijing with a link to satellite ground station in Xinglong that can communicate to another satellite ground station in Nanshan.
The network includes 32 trusted nodes for the fiber network that connect to a total of 109 nodes and servicing 157 users using 700 fiber links. The network is used for Quantum Key Distribution (QKD) and supports an average key generation rate of 47.8 kilobits per second, 40 times higher than the previous rate. The network also has demonstrated a record repeaterless link distance of over 500 kilometers using a technology called twin-field QKD. The network does not currently use quantum repeaters which is still a technology under research. Instead it uses trusted nodes which uses a quantum-to-classical-to-quantum process to repeat the signal. As such, these devices must be located in a tamper proof (or trusted) location so that the signal cannot be intercepted while it is in the classical state.
As a next phase in the development the researchers are aiming to expand the network to international partners in Austria, Italy, Russian, and Canada. For more on this development, you can view a news release from the University of Science and Technology of China here and a technical article available in Nature magazine here.
January 9, 2021