Space station to be quantum communications hub?
点击量： 时间：2019-03-02 12:09:00
By Colin Barras (Image: A Zeilinger) The International Space Station could soon be relaying messages secured using quantum entanglement, if a proposed experiment is accepted by the European Space Agency later this year. If the experiment was successful it would be a step towards unbeatably secure satellite communications between any two points on earth. One form of quantum cryptography exploits the way particles like photons can become “entangled”, into a state where any change to the properties of one affects the other, even across great distances. Einstein famously described it as “spooky action at a distance.” When entangled photons are used to communicate a secret pass-phrase, monitoring their quantum partners makes it possible to know instantly if someone has tried to intercept the message. The current distance record for transmitting entangled photons stands at 144 kilometres, between telescopes in the Canary Islands and Tenerife. The team that set that record, led by Anton Zeilinger at the University of Vienna in Austria, now hopes to smash that figure by transmitting keys over thousands of kilometres using the International Space Station to carry the source of the quantum signals. Their Space-QUEST (Quantum Entanglement for Space Experiments) proposal involves strapping a device containing an ultraviolet laser to the outside of the European Columbus science laboratory on the ISS. That transceiver would generate pairs of entangled photons, transmitting one to each of two receiving stations on the Earth below. “Using a satellite, we can connect between points a few thousand kilometres apart,” says Zeilinger. “Ultimately, we could use quantum cryptography between any two points of the world.” By checking that certain quantum properties of the photon pairs matched,