In 2016 Jian-Wei Pan of the University of Science and Technology of China and colleagues launched Micius into low-Earth orbit to investigate the potential of satellite-initiated quantum communication. Now, just months after setting a distance record for the distribution of entangled photons (see Physics Today, August 2017, page 14), Pan’s team has demonstrated a more important and practical capability: the establishment of a secure quantum communication channel between distant parties. By employing the satellite as a photon emitter and relay, team members in Graz, Austria, and Xinglong, China, developed and shared a 100-kilobyte key that they used to securely exchange photos and hold a video conference.
Micius initiated the link between Graz and Xinglong through a combination of quantum and classical signals, following a version of the BB84 protocol devised by Charles Bennett and Gilles Brassard (see the article by Daniel Gottesman and Hoi-Kwong Lo, Physics Today,...
