Selparis

Recently, physics blogs have been abuzz with the news that Chinese Researchers had teleported photons almost 100 km in free space. This was followed by another claim on May 17th of teleportation between the Canary Islands at a distance of 143 km . Establishing this distance record was remarkable because entangled photons have a habit of getting interfered with and disentangled. But in just focusing on the distance, the discussion neglected a number that was just as important – how accurate was the information transfer? After all, it’s always possible to increase distance while decreasing fidelity.

Quantum Teleportation Diagram

The main intended application of quantum teleportation is cryptography, since data cannot be intercepted (though us science fiction writers can come up with something, surely!), so the accuracy of the information is critical. It is not like a casual video feed, where the loss of a few thousand bits here and there doesn’t render the system useless. So what accuracy did the Chinese physicists achieve? Surprisingly, in half a dozen articles on the subject, only one except for the original paper bothered to mention this key statistic. You can read that article here at physicsworld.com. The answer was 80% – four out of five photons were in the correct state. Considering the distance, that’s really not all that bad. The Canary Island test had slightly less fidelity, as you might expect, but it was in the same ballpark.

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