China Researchers Score Quantum Leaps in Quantum Communications

(AsiaTimes) Chinese scientists have established the world’s first integrated quantum communication network, combining over 700 optical fibers on the ground with two ground-to-satellite links to achieve quantum key distribution over a total distance of 4,600 kilometers for users across the country, Phys.Org reported.
The team, led by Jianwei Pan, Yuao Chen, and Chengzhi Peng from the University of Science and Technology of China in Hefei, reported in Nature their latest advances toward the global, practical application of such a network for future communications.
Another major QKD technology uses the free space between satellites and ground stations for thousand-kilometer-level transmissions. In 2016, China launched the world’s first quantum communication satellite (QUESS, or Mozi/Micius) and achieved QKD with two ground stations 2,600km apart.
Experimentally, TF-QKD has already been performed over 400km of telecom fibers, as well as more than 1,000km of free space through satellite to ground links.
This result is possible thanks to a different way of encoding and retrieving the information in the quantum carriers used for the protocol. In TF-QKD the information is encoded in the phase of the optical pulses prepared by the two users that want to establish the secure communication, and the secret key is retrieved via a single photon interference measurement made by a user in the middle.
In 2017, a more than 2,000km-long optical-fiber network was completed for QKD between Beijing and Shanghai.
Using trusted relays, the ground-based fiber network and the satellite-to-ground links were integrated to serve more than 150 industrial users across China, including state and local banks, municipal power grids, and e-government websites.
Unlike conventional encryption, quantum communication is considered “uncrackable” and therefore the future of secure information transfer for governments, banks, power grids and other sectors.