Researchers say the work, based on the principles of quantum physics, is a step toward using conventional high-speed networks, such as broadband Internet and local-area networks, to transmit ultra-secure video for applications such as surveillance.

The NIST quantum key distribution system uses single photons, the smallest particles of light, in different orientations to produce a continuous binary code, or "key," for encrypting information. The rules of quantum mechanics ensure that anyone intercepting the key is detected, thus providing highly secure key exchange.

The laboratory system produced the "raw" key at a rate of more than 4 million bits per second over 1 kilometer of optical fiber -- twice the speed of NIST's previous record, reported just last month. The record speed was achieved with an error rate of only 3.6 percent.

The work was reported Tuesday, during the International Society for Optical Engineering's Defense and Security Symposium in Orlando, Fla.

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