Canadian scientists help break quantum teleportation distance record

Daily Brew

Last week, an international team of scientists that included researchers from the University of Waterloo, achieved quantum teleportation of a photon - a particle of light - sending it 143 kilometres through open air, breaking the previous 97 km record set in China last month.

Although the project was led by scientists from Vienna's Institute for Quantum Optics and Quantum Information, it used equipment and algorithms that were developed by Professor Thomas Jennewein, Professor Vadim Makarov and PhD student Elena Anisimova, at U of W's Institute for Quantum Computing. During the experiment, Jennewein was in Waterloo, communicating with the rest of the team over Skype as they conducted the teleportation of a photon between two locations in the Canary Islands.

The idea of quantum teleportation was first thought up in 1993, by a team of six scientists that included Charles Bennet, a researcher at IBM, and Gilles Brassard of the University of Montréal. They figured out that they could use 'quantum entanglement' — where two interacting particles make a strange connection that can be maintained even if they are separated by the entire width of the the universe — to make something that's only been in fantasy and science fiction into reality.

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Whether in the lab or outside, the method is roughly the same. You fire a laser beam into a crystal, causing that crystal to spit out two photons that are quantum-entangled with each other - we'll call them 'One' and 'Two'. 'One' is sent to nearby detector that records its collision with another photon, 'Three'. This collision changes both of them so much that they become completely different photons — let's call them 'Eight' and 'Twelve' now — and for all intents and purposes 'One' and 'Three' no longer exist. 'Eight' and 'Twelve' go off on their merry way and the detector sends the 'classical' differences that 'One' and 'Three' had, such as their position and momentum, off to the receiver that 'Two' is headed towards.

As 'Two' is traveling, it immediately knows — through this strange quantum-entanglement connection — that 'One' and 'Three' have collided, and it may also know that 'One' no longer exists!

When 'Two' arrives at the distant receiver, the receiver takes the 'classical' information it received about the collision of 'One' and 'Three' and applies it to 'Two'. In that instant, 'Two' will become an exact copy of 'Three', and since the original 'Three' no longer exists, it can be said that 'Three' has teleported between the detector and receiver.

If this all seems strange and confusing, don't worry. Even Einstein didn't like the idea. He called it "spooky action at a distance" because the information passing between quantum-entangled particles travels faster-than-light, violating his theory of special relativity.

This 143 km achievement is of special significance, because that is roughly the minimum distance at which satellites orbit the Earth.

"The experiment paves the way toward teleportation of signals over free space, or even using satellites," said Jennewein. "This is useful for applications in secure communication, as well as the possibility of networking full-scale quantum computers, once they exist."

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Since there is less interference between the ground and 143 kms straight up into space than there is between two locations 143 kms apart on the ground - due to the atmosphere getting thinner with height, the next stage of the experiment will be to teleport photons between the ground and an orbiting satellite.