Superconducting Single Photon Counter for Quantum Information Processing and Communications

DURIP 2016: PA-AFRL-AFOSR-2016-0001 PI: Gregory Kanter Abstract: For Army Research Office Dr. T.R. Govindan, e-mail: t.r.govindan.civ@mail.mil (919) 549-4236. The Center for Photonic Communication and Computing at Northwestern University is a world leader in quantum communications research, having developed many novel fiber-based devices including the first realizations of a fiber entangled photon source, a high-speed quantum signal switch, and a telecom-band C-Not gate. These systems operate in the ‘telecommunications’ wavelength bands which allows transmission of the photons over long distances. Single photon detectors (SPDs) are eventually used for signal detection. We have employed various SPD technologies in our laboratory including avalanche photodiode based SPDs (gated at both MHz and GHz rates) and SPDs based on upconversion (nonlinear frequency conversion) followed by high quality Silicon APDs. While we have extensive SPD technology in our laboratory, some applications benefit immensely from the new gold standard for SPD performance− detectors based on superconducting technology. Such detectors can have significant performance improvements in detection efficiency, dark count rate, and temporal resolution. A reduction in detection efficiency is equivalent to adding insertion loss, but unlike classical applications where optical amplifiers can largely overcome loss, in quantum optical applications loss is a fundamentally limiting parameter. For other related applications like high photon efficiency communications (many bits transmitted per received photon) and long distance quantum key distribution, efficiency, timing resolution, and dark count rate are all critical metrics. By employing superconducting detectors our group can better leverage novel quantum systems to achieve results impossible with other SPD types. While nanowire superconducting SPDs have fantastic performance, they require inconvenient cryogenic cooling. Recently commercial manufactures have realized small, convenient, and reasonably priced closed-cycle cooling systems for nanowire SPDs allowing complete low-maintenance multi-channel detection systems to be mounted in standard racks. Such advances make these detectors useful laboratory tools that we can exploit for realizing various quantum information processing experiments with record-breaking performance thereby probing new physical effects.