Matthieu Perrenoud

Superconducting-nanowire single-photon detectors (SNSPDs) have enabled the realization of several quantum optics technologies thanks to their high detection efficiency, low dark-counts, and fast recovery time. Here, we will present a 14-pixel SNSPD array with a maximum system detection efficiency (SDE) of 90% that remains above 80% up to 400 Mcps, and we demonstrate the ability to reach detection rates of 1.5 Gcps with an absolute SDE of 45%. Furthermore, we will explain how such device has been integrated in a QKD set-up and enabled high-speed QKD, with secret-key rates exceeding 60 Mbps over a distance of 10 km. Moreover when used in a QKD setup, the array can improve resilience against blinding attacks by monitoring the coincidence clicks between the pixels. Finally we will show that the detector is able to distinguish few-photon number states in an optical pulse with high fidelity, without posing strict limitations on the shape of the incoming light. We achieve a 2-photon fidelity of 74% and 57% for a 3-photon state, which represent state-of-the-art results for fibre-coupled SNSPDs. Such detectors could find immediate application in LOQC protocols where the capability to distinguish few photon-number states is sufficient – that is, either ‘1’ vs ‘more than 1 photons’.