secret quantum codes, page 1

secret quantum codes

www.sciam.com

Researchers hope to send an experiment to the International Space Station (ISS) by the middle of the next decade that would pave the way for transcontinental transmission of secret messages encoded using the mysterious quantum property of entanglement.

When two particles such as photons are born from the same event, they emerge entangled, meaning they can communicate instantaneously no matter how far apart they are. Transmitting entangled pairs of photons reliably is the backbone of so-called quantum key distribution—procedures for converting those pairs into potentially unbreakable codes. Quantum cryptography, as it is known, could appeal to banks, covert government agencies and the military, and was tested in a 2007 Swiss election.

Photons can travel perhaps 100 miles (160 kilometers) or so along today's fiber-optic cables before their quantum character breaks down. That limit vanishes aboveground. Last year, a team led by physicist Anton Zeilinger of the University of Vienna transmitted quantum keys up to 89.5 miles (144 kilometers) between a pair of telescopes in Spain's Canary Islands.

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