Experiment With Chinese Satellite Demonstrates Quantum Weirdness Over Record Distances

By Ryan F. Mandelbaum on at

Quantum mechanics is weird as hell, where the rules of the world you experience don’t apply. Even at distances a thousand kilometres apart, particles seem to be able to communicate with each other.

Chinese scientists have made an extreme test of this proof, testing what Albert Einstein’s called “spooky action at a distance” between stations receiving light beams from satellites. The research smashes previous records of 100 kilometres apart. Don’t expect this sort of stuff to have any influence on your life just yet—but in the future, it could have some important quantum computing applications.

So, what’s going on?

The mathematics of quantum mechanics comes along with this weird property of entanglement, where particles can take on related properties if they end up in an equation together. But if you separate these particles spatially, then they remain entangled with these properties until you observe one of them—then the other particle assumes its corresponding value. It’s as if the fact that you observed the first particle immediately transmits information to the other particle on how it should look.

That’s why Einstein called it spooky action at a distance, because it’s spooky and the particles somehow seem to communicate over a distance. And he didn’t want to believe the effect was real.

Experiments done since the 1970s have indeed proven that this spooky action at a distance exists, but these prior tests required optical fibres that weakened the signal. This time around, however, the Chinese team used their newly-launched Micius satellite, which allowed them to send the photons unobstructed through the void of space. They published their result in the journal Science today.

The experiment itself is a really, really roundabout way of performing these observations. The team had several ground stations and a satellite. The satellite contains a laser with a device to split the beam, then passing through a special crystal in order to entangle the pairs of photons. The two beams then travel to two different laboratories, up to 1,200 kilometres (750 miles) apart. The researchers then open up the box at the laboratories and compare.

Other physicists were impressed, but it’s important to note that only one in six million photons were accurately recovered, Alexander Ling, a physicist at the National University of Singapore told Science. But even this is a huge step above the previous ground-based experiments, the team’s head scientist Jian-Wei Pan from the University of Science and Technology of China in Hefei told Scientific American.

You’re probably wondering what use these satellites would actually have. One possibility is that entangled photons could be important for telecommunications. If someone tried to intercept data sent over one of these quantum lines, the receiver would immediately know, since they’d receive un-entangled data.

So, technologically, this is a huge step as Jürgen Volz, physicist at the Vienna Center for Quantum Science and Technology told the LA Times. But it’s still a long, long time before we’ll actually see this technology used in our communications networks. [Science via Scientific American]

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