Quantum encryption arrives

BBC reports: [brutally precised]

Perfect secrecy has come a step closer with the launch of the world's first computer network protected by unbreakable quantum encryption at a scientific conference in Vienna. The network connects six locations across Vienna and in the nearby town of St Poelten, using 200 km of standard commercial fibre optic cables.

The basic idea of quantum cryptography was worked out 25 years ago by Charles Bennett of IBM and Gilles Brassard of Montreal University, who was in Vienna to see the network in action.

"All quantum security schemes are based on the Heisenberg Uncertainty Principle, on the fact that you cannot measure quantum information without disturbing it," he explained.

"Because of that, one can have a communications channel between two users on which it's impossible to eavesdrop without creating a disturbance. An eavesdropper would create a mark on it. That was the key idea."

In practice this means using the ultimate quantum objects: photons, the "atoms of light". Incredibly faint beams of light equating to single photons fired a million times a second raced between the nodes in the Vienna network.

From the detected photons, a totally secret numerical key can be distilled, which encodes the users' data much like the keys used in normal computer networks do. The advantage is that no-one else can know the key without revealing themselves.
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