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NIST Quantum Cryptography Highlighted in New Journal of Physics

Recent research has shown that the security of a key string of finite length can only be assured for key strings of relatively long lengths, and this understanding has underscored the importance of high-speed systems that maximize key production rates. The successful efforts at NIST in quantum information research are represented in two articles in the latest issue of the New Journal of Physics: Focus on Quantum Cryptography: Theory and Practice.

In the first article, "1310 nm differential-phase-shift QKD system using superconducting single-photon detectors", generated in the collaboration between ITL and EEEL, reports the use of the high timing resolution (<100 ps) of superconducting nanowire single-photon detectors to demonstrate a 2.5 GHz quantum key distribution (QKD) system operating at 1310 nm. This wavelength is particularly well suited for high-speed and long-distance QKD in optical fiber when the same fiber is being used for 1550-nm telecommunications signals. The detection system is shown to significantly outperform schemes based on silicon avalanche photodiodes, and supports siftedkey production rates up to 10 kbit/s over 50 km of fiber.

The second article, "Programmable instrumentation and gigahertz signaling for single-photon quantum communication systems", reports the results from the collaboration between ITL and PL in data-handling electronics necessary to support the operation of QKD and other single-photon-communication systems at GHz rates. Providing subnanosecond time tags at such rates can result in significant amounts of data for processing, and NIST systems, based on field-programmable gate arrays, perform QKD post-processing at rates sufficient to produce quantum-generated key bits at rates above 1 Mb/s. Significant advances in timing resolution at high counting rates are achieved with time-division demultiplexing techniques from telecommunications practice, and systems under test can realize 100 ps detection time bins at count rates in the GHz regime.