June 2006

EEEL, ITL, and PL Researchers Demonstrate Record Data Rates for Superconducting Single Photon Detectors in QKD System

Quantum cryptography is the exchange of information using techniques whose security is determined by the laws of quantum mechanics rather than by mathematical complexity. Quantum mechanics offers the potential for secure communication because measurement of an unknown quantum system changes its state. A team of EEEL, ITL, and PL researchers recently demonstrated the operation of a superconducting single photon detector (SSPD) system in a high-speed NIST Quantum Key Distribution (QKD) link, which was originally equipped with silicon-based single photon detectors. ("http://www.nist.gov/public_affairs/releases/quantumfiber.htm"). The link operated at a system clock rate of 625 Mbps through 1 km of optical fiber. The laboratory system produced this "raw" sifted key at a rate of 1 million bits per second, roughly a quarter of the speed of NIST's recently reported record breaking performance. However, the error rate from this SSPD system was significantly lower, 1 % as opposed to 3.6 %. The lower error rate results in a secret key generation rate of better than a third of the high speed system (800 kbps vs. 2 Mbps). The lower error rate is a direct result of lower jitter in this type of detector. Based on the results from this work, it should be possible to implement a QKD link with superconducting-based detectors at a clock rate 5 times faster than the existing silicon-based detector system. Another major advantage is that the superconducting single photon detector can be used at common telecommunication wavelengths (1550 nm and 1310 nm). At these wavelengths, fiber incurs lower optical loss and therefore allows longer transmission distance than at wavelengths shorter than 1 micrometer where the silicon-based detectors operate.

This is a very successful inter-OU collaboration. The team will continue to work together on research and development of future quantum communication technologies.

Contact: Sae Woo Nam, 303-497-3148 (Boulder), Xiao Tang, 301-975-2503