Synchronous single-photon detection with GHz-gated superconducting nanowire detectors.

We demonstrate a GHz-gated operation of superconducting nanowire single-photon detectors suitable for synchronous applications. In comparison with conventional dc-biased nanowire detectors, this method prevents the detector from latching and can suppress dark counts and background noise. Using a gating frequency of 3.8 GHz and a fast, synchronized laser diode, we show that the detector's operation point follows the oscillating current and its detection efficiency depends on the relative frequency and phase of the bias and modulated optical signal. The obtained experimental results are in good agreement with simulations, showing that the duty cycle of a gated detector can be adjusted in a wide range in case of a pronounced saturation of the current-dependent detection efficiency. This operation mode could be suitable for applications such as quantum key distribution and time-of-flight laser ranging.