A team from Moscow State Pedagogical University in Moscow, Naval Research Laboratory in Washington, NPTest Inc. in San Jose, Calif., and the University of Rochester in Rochester, N.Y., has reported results of a series of tests on nanostructured NbN superconducting single-photon detectors. The findings point to means of improving the performance of the devices at infrared wavelengths for quantum key distribution and other applications.The experiments included measurements of quantum efficiency, gigahertz counting rate, jitter and noise-equivalent power at various visible and near-IR wavelengths and at an operating temperature of 4.2 K. The scientists conclude that lowering the operating temperature or enhancing photon coupling with the use of a quarter-wave resonator or a backreflector should increase the quantum efficiency in the IR. The incorporation of a resonator also would decrease unwanted counts, they note.