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China Uses Quantum Physics for Secure Long-range, Satellite-based Communications

22 Jul 2020, 22:14 UTC
China Uses Quantum Physics for Secure Long-range, Satellite-based Communications
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BEIJING (Chinese Academy of Sciences PR) — The exchange of a ‘secret key’ for encrypting and decrypting messages over a distance of 1,120 kilometres is reported in Nature. (Paper)

This achievement is made using entanglement-based quantum key distribution, a theoretically secure communication technique. Previous attempts to directly distribute quantum keys between two ground users under real-world conditions have reached distances of only around 100 kilometres.

Quantum communication uses photons to securely distribute a ‘secret key’ to allow the exchange of encrypted messages. Previous work has demonstrated quantum key distribution along up to 404 kilometres of coiled optical fibre in a laboratory, or from a satellite to a ground station up to 1,200 kilometres away.

However, real-world application between two users has been limited to around 100 kilometres. This is due to photon losses, which increase rapidly with distance. Trusted relays or ‘repeaters’ offer a way to extend the distance and avoid photon loss, but the relay stations introduce security risks.

Jian-Wei Pan and colleagues circumvent the need for repeaters by using a satellite to establish a secure link between two ground stations on Earth, using entangled photons. Entangled photons are linked in such a way that, even when separated ...

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