Quantum Satellite Secures Communications

A Chinese quantum satellite has dispatched transmissions over a distance of 1,200 km (746 miles), a dozen times further than the previous record, a breakthrough in a technology that could be used to deliver secure messages, state media said on Friday.

China launched the world’s first quantum satellite last August, to help establish “hack proof” communications between space and the ground, state media said at the time.

The feat opens up “bright prospects” for quantum communications, said Pan Jianwei, the lead scientist of the Chinese team, Quantum Experiments at Space Scale (QUESS), according to the official Xinhua news agency.

The scientists exploited the phenomenon of quantum entanglement, in which a particle can affect a far-off twin instantly, somehow overcoming the long distance separating them, a situation termed “spooky action at a distance” by the Nobel-prize winning physicist Albert Einstein, Xinhua added.

The team had successfully distributed entangled photon pairs over 1,200 km, it said, outstripping the distance of up to 100 km (62 miles) at which entanglement had previously been achieved.

The technology so far is “the only way to establish secure keys between two distant locations on earth without relying on trustful relay,” Pan told Xinhua, referring to encrypted messages.

The new development “illustrates the possibility of a future global quantum communication network” the journal Science, which published the results of the Chinese team, said on its website.

Source: http://www.reuters.com/

The First Satellite Using Quantum Cryptography Is Chinese

Congratulations are in order for China: by launching the world’s first quantum communications satellite, the country has achieved an interesting — if somewhat difficult to explain — milestone in space and cryptography.

quantum dots

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.

So what’s in the package that’s so exciting?

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 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.

Source: https://techcrunch.com/