Privacy, courtesy of quantum physics

Privacy, courtesy of quantum physics Micius, China’s pioneering quantum-tech satellite, has broken new ground by sharing an unbreakable, eavesdropper-proof encryption key across more than 1,000 kilometers. The spacecraft accomplished the feat of cryptography by beaming entangled photons to two separate ground stations simultaneously — a technology called quantum key distribution (QKD). To be of practical use, future quantum satellites will need to fly higher and distribute encryption keys at a much faster rate than Micius can. But its recent feat is “the most advanced QKD demonstration so far”, writes quantum-computing researcher Eleni Diamanti. Nature News & Views | 6 min read Read more: China's quantum satellite clears major hurdle on way to ultrasecure communications (Nature, from 2017) Reference: Nature paper

Pairs of entangled photons are produced on board the satellite Micius. The photons in each pair are then sent to 2 optical ground stations that are separated by a distance of 1,120 kilometres. This process enables parties at the two stations to share a string of bits called a key, which they can use to encrypt and decrypt secret messages with absolute security.