Itoero Posted August 15, 2017 Posted August 15, 2017 (edited) Less than a year after they launched the world’s only quantum communications satellite, Chinese researchers have for the first time ever sent entangled photons from space to ground stations on Earth. “This is the first step towards worldwide secure quantum communications, and maybe even a quantum internet,” says Anton Zeilinger, an expert on quantum physics at the University of Vienna in Austria. One of the building blocks of a secure quantum network is the ability to exchange entangled photons between two parties. When a pair of photons are entangled particles, measuring one instantly influences the state of the other, regardless of the distance between them. To create a cryptographic key, the two parties, say Alice and Bob, use the results of a series of measurements on pairs of entangled photons. The key can then be used to encrypt messages that are sent over a regular channel. The duo can also detect the presence of an intruder who tries to intercept and retransmit the entangled photons, because doing this destroys the entanglement. Last year, researchers in China established a record separation between Alice and Bob: entangled photons were exchanged over a distance of 404 kilometres using non-commercial, high-quality optical fibre. https://www.newscientist.com/article/2134843-chinese-satellite-beats-distance-record-for-quantum-entanglement/ Edited August 15, 2017 by Itoero
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