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Friday, August 10, 2012

Researchers use teleportation to beam a single photon 97km

Two teams of researchers have extended the reach of quantum teleportation to unprecedented lengths.

The groundbreaking research could be a step towards creating quantum computers and other technology operating at speeds far in excess of current limits.

And while teleporting humans may still be a long way off, researchers believe the latest work is a big step forward.

The team was able to teleport a qubit (a standard unit of data in quantum computing) 97 kilometers across a lake using a small set of photons without fiberoptic cables or other intermediaries.

They used a complex laser targetting device for the experiment.

Quantum teleportation relies on a phenomenon known as entanglement, through which quantum particles share a fragile, invisible link across space.

Two entangled photons, for instance, can have correlated, opposite polarization states—if one photon is vertically polarized, for instance, the other must be horizontally polarized.

But, thanks to the intricacies of quantum mechanics, each photon’s specific polarization remains undecided until one of them is measured.

At that instant the other photon’s polarization snaps into its opposing orientation, even if many kilometers have come between the entangled pair.

This is the phenomenon that scientists believe can be harnessed for quantum teleportation.

The group Chinese group created entangled photons by stimulating a crystal with ultraviolet light.

This produces a pair of photons with the same wavelength, but opposite (and unknown) polarization values.

One photon was sent 97km across Qinghai Lake (using a telescope to focus the beam), while the second was analysed locally, according to the team's research paper, published in Nature.

 Using these photons, the researchers copied the quantum state from the laboratory to the far station, achieving quantum teleportation over a much larger distance than previously obtained.

The laser targeting device developed by Juan Yin  was necessary to counteract the minute seismic and atmosphere shifts that would otherwise break the link between the two remote locations.

That distance surpasses the previous record, set by a group that included several of the same researchers, by 16 kilometers.

However, a second team has already bettered it.

A European and Canadian group claims to have teleported information from one of the Canary Islands to another, 143 kilometers away. However, the paper has not been peer-reviewed or published.

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