The ability to send perfectly secure messages from one location on the planet to another has obvious and immediate appeal to governments, the military and various commercial organisations such as banks. This capability is already possible over short distances thanks to the magic of quantum cryptography, which guarantees the security of messages, at least in theory.
For the moment, however, quantum cryptography works only over distances of 100 km or so. That’s how far it is possible to send the single photons that carry quantum messages through an optical fibre or through the atmosphere.
Last year, we watched as European and Chinese physicists battled to claim the distance record for this technology with the Europeans finally triumphing by setting up a quantum channel over 143 kilometres through the atmosphere.
That distance is a good fraction of the way into space. And the reason that’s important is that it’s a stepping stone to sending quantum messages to orbiting satellites which can then route the messages to almost anywhere else on the planet.
Today, the Chinese claim another small victory in this quantum space race. Jian-Wei Pan at the University of Science and Technology of China in Shanghai and a few pals say they’ve bounced single photons off an orbiting satellite and detected them back on Earth. That’s significant because it simulates a satellite sending single photons from orbit to the surface, crossing off another proof-of-principle milestone in their quantum checklist.
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