China launches the first quantum communications satellite

China's successful launch of the world’s first quantum communications satellite, the country has achieved an interesting — if somewhat difficult to explain — milestone in space and cryptography.

"The event is indeed very exciting and does carry global importance because this would be the first such experiment," said Alexander Sergienko, a professor of electrical and computer engineering at the Boston University.

Sergienko said the quantum communication race has been going on for the last 20 years since the initial demonstration of quantum key distribution link under Lake Geneva in 1995.

After that, metropolitan secure communication networks have been developed and demonstrated in Boston, Vienna, Beijing, and Tokyo, and many more examples of quantum metropolitan networks have been demonstrated in the last five years covering Canada, Italy, U.K. and Australia, he said.

Quantum Experiments at Space Scale (QUESS), nicknamed Micius after the philosopher, lifted off from Jiuquan Satellite Launch Center at 1:40 AM local time (late yesterday in the U.S.) and is currently maneuvering itself into a sun-synchronous orbit at 500 km

QUESS is an experiment in the deployment of quantum cryptography — specifically, a prototype that will test whether it’s possible to perform this delicate science from space. 

Inside QUESS is a crystal that can be stimulated into producing two photons that are “entangled” at a subatomic, quantum level. Entangled photons have certain aspects — polarization, for example — that are the same for both regardless of distance; if one changes, the other changes. The how and the why are beyond our pay grade here, so just take entanglement as a given.

The trouble is that photons are rather finicky things, and tend to be bounced, absorbed, and otherwise interfered with when traveling through fibers, air, and so on. QUESS will test whether sending them through space is easier, and whether one of a pair of entangled photons can be successfully sent to the surface while the other remains aboard the satellite.

If this is possible, the entangled photons can be manipulated in order to send information; the satellite could, for example, send binary code by inverting its photon’s polarization, one way for 1, the other way for 0. The ground station would see its photon switching back and forth and record the resulting data. This process would be excruciatingly slow, but fast enough for, say, key creation and exchange — after which data can be exchanged securely by more ordinary means.

The critical thing about this is that there is no transmission involved, or at least not one we understand and can intercept. Whatever links the two photons is intangible and undetectable — you can’t entangle a third one to listen in, and if even if you managed to interfere with the process, it would be immediately noticed by both sides of the process, which would see unexpected changes to the photons’ states.

As you can imagine, an undetectable and perfectly secure channel for digital communications is of enormous potential value for an endless list of reasons. China is early to the game with QUESS, but they’re not the only ones playing. Other quantum satellites, though none quite so advanced, are in the ether right now, and more are sure to come.


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About Jaime Lacson

A Freelance Computer Tech with knowledge about computer, router and mobile phones, especially in Upgrade and Downgrade OS, Software and Hardware troubleshooting. follow me at Google+
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