Fiber Integrated MgB2 Single Photon Detectors

Research Project, 2020 – 2023

High response rate single photon detectors form the baseline for the Quantum Key Distribution (Quantum Encryption), Space-to-Ground laser links, quantum informatics, biomedical studies. Based on the short reset time, low dark (false) counts, and high quantum efficiency Superconducting Single Photon Detectors (SSPD) overperform their semiconducting counterparts at both the visible and communication wavelengths. Yet, despite of great efforts, state of the art SNSPDs, made from low Tc superconducting films (NbN, NbTiN, NbC, WSi, etc.), still have a reset time limited to 1-10ns. This is far from the GHz count rates predicted from the studies of the superconducting state recovery rates. In our previous studies we have shown that thanks to the much lower (1/60) kinetic inductance in thin MgB2 films, large area SNSPDs, made from MgB2 nanowires, demonstrate an extrinsic (actually observed) reset rate 2 nanowire detectors operate in the single-photon mode at λ=1550nm.In this project we will explore this findings in an attempt to merge the long sought-after combination of properties (high quantum efficiency and multy-GHz count rate) in a proof of concept fiber-integrated MgB2 SNSDP. This will be achieved by exploring quantum detection in superconducting nanowires at the pair-breaking critical currents and integration of MgB2 nanowires in optical cavities.