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A new quantum teleportation distance record has been set

Scientists just teleported information over 100 km of fibre!

FIONA MACDONALD
24 SEP 2015
 

Researchers in the US have successfully teleported information encoded into particles of light over 100 kilometres of optical fibre, smashing the previous distance record of 25 km.

That doesn't mean that matter was teleported, so we're no closer to being able to teleport people or objects (sorry guys), but this type of quantum teleportation could help to greatly improve the security and strength of Internet connections. 

 

Researchers first proposed quantum teleportation around 20 years ago, and it relies on a phenomenon known as quantum entanglement, where two particles are inextricably linked, which means their states can only be defined by being the opposite of one another.

Because particles don't have a defined state until they're measured, this means that as soon as one particle is measured its state will be set, and this will instantly change the state of its entangled partner, even when they're separated by great distances, resulting in super-fast communication.

In the past, researchers have managed to teleport information encoded in photons over greater distances than this through free space, but this experiment used optical fibre, which means that their technique could potentially be used to create a quantum Internet network, using existing infrastructure.

The experiment itself is a little hard to explain, but thankfully the researchers from the US National Institute of Standard and Technology have outlined their method in this easy-to-digest infographic.

nist quantum teleportation infographic fullsize

Let's break that down even further. So what happened is that the scientists created two entangled photons and sent one - the "output photon" - over 102 km of optical fibre.

They then determined the state of the other entangled "helper photon" by bouncing it off a photon that they already knew the state of. The 'state' of the photons in this case was whether they hit the detector 'early' or 'late' - a timeframe separated by only 1 nanosecond.

Once they'd worked out the state of the helper photon, they the  knew the state of the output photon, and they used detectors on the other end to confirm this.

It's not a new experimental set-up, but what's different is that those detectors, which were made especially by the team to pick up single photons, allowed them to send the information further than ever before.

"Only about 1 percent of photons make it all the way through 100 km of fibre," one of the researchers, Marty Stevens, said in a press release. "We never could have done this experiment without these new detectors, which can measure this incredibly weak signal."

Before this, researchers would lose so much quantum data in optical fibres that they couldn't send information over more than 25 km. 

So what does all of this mean for us playing along at home? This new teleportation technique could lead to devices call quantum repeaters. These would be like the repeaters we currently use in our networks, which receive a signal and then retransmit it at a higher level, to make our information travel around the whole world.

A quantum repeater would do the same thing, but with quantum information, and they could potentially extend the reach far enough to build an entire "quantum Internet", which would be faster, more efficient, and more secure than the networks we rely on today. 

While we're still a long way off building a whole network made up of entangled light particles, it's a pretty great demonstration of the potential. 

The results have been published in the journal Optica.

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