Highlights of the year
Researchers in China and Austria used a satellite link to hold the first intercontinental videoconference protected by quantum cryptography (see Focus: Intercontinental, Quantum-Encrypted Messaging and Video). The data security was provided by quantum key distribution (QKD), which exchanges cryptographic keys that are encoded in quantum-entangled photons. Long-distance QKD has been previously demonstrated on terrestrial networks of optical fibers, but optical losses in the fibers had limited the communication distance to a few hundred kilometers. Exploiting the undisturbed propagation of photons in space, the satellite experiment involved two stations that were 7600 km apart. Exchanging secret keys at kilohertz rates, the teams were able to send quantum encrypted images and to hold a secure videoconference that lasted 75 minutes and required 2 gigabytes of data. The demonstration is good news for those who envision a “quantum internet” built around a global network of ground stations and satellites.