Gaithersburg, MD, May 4, 2004--The fastest known cryptographic system based on transmission of single photons has been demonstrated by a team at the Commerce Department's National Institute of Standards and Technology (NIST). The NIST quantum key distribution (QKD) system transmits a stream of individual photons to generate a verifiably secret digital key at a rate of 1 million bits per second (bps), which is about 100 times faster than previously reported systems of this type.
The demonstration, described in the May 3 issue of Optics Express, is the first major reported result from a new NIST testbed built to demonstrate quantum communications technologies and cryptographic key distribution. The testbed provides a measurement and standards infrastructure for research, testing, calibrations and technology development. Scientists tested the QKD system by generating an encryption key that could be sent back and forth between two NIST buildings that are 730 meters apart. They are using the testbed to develop data-handling techniques associated with this type of encryption.
Compared to previously described QKD systems, the major difference in the NIST system is the way it identifies a photon from the sender among a large number of photons from other sources, such as the sun. To make this distinction, scientists time-stamp the QKD photons, then look for them only when one is expected to arrive.
"To be effective, this observation time has to be very short," says NIST physicist Joshua Bienfang. "But the more often you can make these very brief observations, then the faster you can generate keys. We have adapted some techniques used in high-speed telecommunications to increase significantly the rate at which we can look for photons."
Acadia Optronics LLC of Rockville, Md., consulted on the system design and hardware. Partial funding for the project was provided by the Defense Advanced Research Projects Agency.