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QI: Fachverband Quanteninformation

QI 36: Poster – Quantum Information (joint session QI/Q)

QI 36.12: Poster

Donnerstag, 13. März 2025, 17:00–19:00, Tent

Synchronizing Detector Dead Times to Accelerate Quantum Key Distribution — •Maximilian Mengler, Maximilian Tippmann, and Thomas Walther — TU Darmstadt, Institute for Applied Physics, 64289 Darmstadt

Most Quantum-key-distribution setups consist of photon detection systems with multiple single-photon detectors. Upon measuring a photon these detectors will enter a dead time but due to security reasons only events that are registered when all detectors are ready may contribute to a key for various protocols, e.g. BBM92. This especially constrains systems relying on cheaper detectors like single-photon-avalanche-diodes because of the detectors' long dead times. At high detection rates, two detectors might block each other alternately with one detector entering a new dead time before the other finished its own. We implement a method that utilizes inverse gating signals sent to all detectors upon registration of an incident photon. This leads to the synchronization of the detectors' dead time and ensures that all the detectors are active for the maximum amount of time. We tested this method with our QKD system for various losses between the receiving parties and investigated its effect. In doing so, we were able to increase the secure key rate by up to 75%.

Keywords: QKD; Gating; Deadtime; Single photon avalanche diodes