Researchers from the University of Geneva in Switzerland and Corning Inc. have set a new distance record for quantum key distribution (QKD) using a new prototype capable of distributing quantum keys over a distance of 250 km in a lab, 50 km greater than the previous record. The researchers hope to soon be able to distribute quantum keys over intercity distances of 300 km.
To achieve the new record, three major improvements were made to the QKD technique. First, the researchers developed a coherent one way protocol designed specifically for quantum communication over optical fiber networks. Second, the researchers used an improved superconducting single-photon detector to decrease noise. Third, ultra low loss fibers made by Corning were used to minimize channel loss and improve the distribution rate. These improvements enabled the researchers to distribute quantum keys in the lab at a rate of 15 bits per second over 250 km of optical fiber, or about 6,000 bits per second over 100 km, with low error rates. The fully-automated system is capable of running for hours without human intervention.
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