While people get excited about future internets being powered by quantum particles, nobody really knows how that's going to work yet. But Chinese physicists have taken a step in the right direction, by creating the world's first quantum router.


If it can be made to work on a large scale, quantum information will transform the way we send data: instead of sending just the 0s and 1s of digital code, quantum communication can send information in a superposition of states that represent both 0s and 1s at the same time. It's cool, and it's crazy.


Currently scientists can only send photons carrying quantum information over the length of a single optical fibre; they can't transfer the photons into a different pipe, which is a process known as routing. Normally, that process—including the way it's done in your home router—requires reading data from within the transmission, known as a control signal, which determines where the information can be sent.

The trouble is, reading a control signal in the quantum world actually destroys it—making it impossible to route using data embedded within the signal. In turn, that means using non-quantum control signals, which means losing out on many of the benefits of using quantum information in the first place.

The new device, offered up by Tsinghau University in China, creates a quantum photon, that is a superposition of two separate photons that are in horizontal and vertical polarized states. That quantum photon is then converted into two, lower power, photons, which both also share the same dual polarization. Then, a router can read data from one photon, which it destroys, and use the remaining one as the data signal.

It might sound simple, but its output may seem a little odd to the casual observer: what gets spit out is actually a probabilistic result, which isn't always the same. But then, that's just how the quantum world works. There is one snag, though: the device can only handle one quantum bit of data at a time, which makes it a proof-of-concept and little more.


Still, it's further than anyone else has managed to venture down the path to a quantum internet—we just still don't know how it will turn out when we get there. [arXiv via Technology Review]

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