One of the biggest hurdles to implementing quantum cryptography has been vaulted, with researchers finding a way to transmit the key over a non-dedicated connection.  Previously because of the inherent noise in a fibre channel transmitting general data the key would be lost and so a separate fibre channel was needed which only the keys were able to transmit but thanks to researchers at Toshiba’s Cambridge Research Laboratory it is now possible to send the keys on existing fibre which also carries other data.  They have created a detector which can open for a mere 100 millionths of a micro-second and receive the key, with the detection window being so quick there is not time for noise to interfere and the wrong photon be detected as the key.  The Register reports they can transmit keys over a line running at 500kbps for 50km and still have the key properly detected.

"Traditionally it has been necessary to use dedicated fibre to send the single photons (particles of light) that are required for Quantum Key Distribution (QKD). This has restricted any applications of quantum cryptography technology to specialist and small-scale systems in banks and high-level government, essentially because of the extra inconvenience and cost required in allocating a dedicated fibre strand for quantum key distribution."

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