A low-noise single-photon detector for long-distance free-space quantum communication

Abstract

We build and test a single-photon detector based on a Si avalanche photodiode Excelitas 30902SH thermoelectrically cooled to −100 ∘ C. Our detector has dark count rate below 1\xa0Hz, 500 μ m $500\\ \\mu\\mathrm{m}$ diameter photosensitive area, photon detection efficiency around 50%, afterpulsing less than 0.35%, and timing jitter under 1\xa0ns. These characteristics make it suitable for long-distance free-space quantum communication links, which we briefly discuss. We also report an improved method that we call long-time afterpulsing analysis, used to determine and visualise long trap lifetimes at different temperatures.