Chinese scientists claim they've demonstrated photon entanglement over a distance of 1,200km, with one of the nodes used in the experiment located on a satellite.
Photons can be split and when that's done, the resulting pair of particles are blank slates but are entangled so the impact of anything you do to one can be observed in the other. Dubbed “spooky action at a distance” by Albert Einstein, entanglement has been demonstrated on Earth. While entanglement is not fully understood, it's hoped that once we grok it properly it could offer a kind of quantum back channel for applications like distributing encryption keys.
Earthbound experiments have largely seen entanglements unravel over distances of about 100km. But China last year launched a satellite named Micius to test whether entanglement can work across long distances and through space.
Now the journal Science has published a paper, Satellite-based entanglement distribution over 1200 kilometers, in which Chinese scientists suggest entanglement can be established over long distances. The paper says the experiment demonstrated “satellite-based distribution of entangled photon pairs to two locations separated by 1203 kilometers on Earth, through two satellite-to-ground downlinks with a summed length varying from 1600 to 2400 kilometers.” It continues, “effective link efficiency is orders of magnitude higher than that of the direct bidirectional transmission of the two photons through telecommunication fibers.”
State-run organ Xinhua reports “the effective link efficiency of the satellite-based approach is 12 and 17 orders of magnitude higher respectively.”
We are of course years, if not decades, from putting this stuff into production, but the results hint that photon-schlepping satellites might one day become a feature of decent security. If the whole idea of encryption hasn't been blasted out of the sky by politicians by then, anyway.
While we wait for that little mess to be sorted out, China may also offer us some insights into black holes or pulsars with the Hard X-ray Modulation Telescope it successfully launched on Thursday. The orbiting observatory packs a high, medium and low energy X-ray telescopes that can survey energy bands from 1 keV to 250 keV, across an area of 5,000 square centimetres. China reckons no similar scope can survey a larger area and so hopes it will let us get a long, hard, look at black holes, pulsars and gamma-ray bursts. ®