The first quantum transmission to go via space paves the way for ultra-secure communications satellites. Secret encryption keys transmitted via quantum links provide the ultimate way to communicate securely. That's because any attempt to intercept the key will be revealed thanks to the laws of quantum mechanics, which say that interception will introduce changes that give away eavesdroppers.
The technology is already available for fibre-optic cables, but a truly global network would need satellites to beam quantum data between distant locations. To test how these might work, Paolo Villoresi at the University of Padua in Italy and his colleagues turned to satellites covered in ultra-reflective mirrors. These are normally used to bounce laser beams back to Earth. The time they take to return shows up any shifts in gravity.
Via Dr. Stefan Gruenwald