On August 1, China launched their Quantum Experiments at Space Scale (QUESS) satellite from the Jiuquan Satellite Launch Center in the Gobi Desert. This satellite, a joint Austrian-Chinese collaboration, is intended to facilitate long-distance experiments in quantum optics, to allow the development of secure quantum-encryption communications and quantum information teleportation technology. On August 19, Beijing’s control center successfully received 202 megabytes of data from the satellite, nicknamed Micius after the 5th century Chinese scholar, secured using quantum encryption keys.
Quantum encryption keys are a method of securing traditional communications using the principle of quantum entanglement that allows the receiver of the data to know if the data has been intercepted while in transit: in this case, two streams of quantum-entangled pairs of photons are produced by laser equipment on the satellite, and then one of the beams is sent to the party transmitting the information, and the other is sent to the receiver. The spin-state of the paired photons are used to create the encryption code itself, and if both parties in the transmission are seeing identical key-codes, they know the transmission is secure.
But if the key-codes fall out of sync, then the parties know that someone’s listening in on the transmission: because this process relies on a quantum-based process, any attempt to measure the spin-state of the transmitted photons will immediately change that spin-state, and throw the codes out of sync. Measuring the spin-states by the parties transmitting and receiving the data isn’t a problem, but if one of the photon streams is intercepted by a third party, the code changes, and they’ll know to cut the transmission.
Because of the nature of QUESS’s light beams, it can only make line-of-sight communications, and can also only do so while it is not exposed to sunlight — solar radiation will interrupt the fragile state of the photon stream’s spin states. If the QUESS project is successful, it is expected to be followed by the launch of a series of satellites that will be used to produce a European–Asian quantum-encrypted network by 2020.
To see where the QUESS satellite is in its orbit for yourself, visit stuffin.space.
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