Mainz 2026 – scientific programme
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Q: Fachverband Quantenoptik und Photonik
Q 59: QuanTour V – Protocols
Q 59.3: Talk
Thursday, March 5, 2026, 15:15–15:30, P 7
Deployed entanglement-based BBM92 quantum key distribution using frequency-converted photons emitted by a quantum dot — •Michal Vyvlecka1, Raphael Joos1, Benjamin Breiholz1, Aurélien Marmasse1, Ilenia Neureuther1, Timo Schnieber1, Anna Frederike Köhler1, Tim Strobel1, Tobias Bauer2, Marlon Schäfer2, Nand Lal Sharma3, Caspar Hofmann3, Simone Luca Portalupi1, Christoph Becher2, and Peter Michler1 — 1Institut für Halbleiteroptik und Funktionelle Grenzflächen, Center for Integrated Quantum Science and Technology (IQST) and SCoPE, 70569 Stuttgart, Germany — 2Fachrichtung Physik, 66123 Saarbrücken, Germany — 3Institute for Integrative Nanosciences, 01069 Dresden, Germany
We implemented an entanglement-based BBM92 quantum key distribution (QKD) protocol over approximately 700 m across the university campus buildings using the existing deployed fiber network. The entangled-photon pair at wavelength of 780 nm was emitted by an epitaxially grown droplet-etched GaAs quantum dot (QD) embedded in a dielectric antenna. The QD was excited via two-photon excitation using a pulsed laser that emits 10 ps pulses at 779 nm with a 380 MHz repetition rate. To minimize losses in silica fibers, we employed bidirectional, polarization-conserving quantum frequency conversion to shift the QD emission to a telecom wavelength. We achieved stable QKD operation for more than 10 hours, with a raw key rate exceeding 200 Hz and a quantum bit error rate below 4.5 %. After error correction and privacy amplification, we distilled a secure key at a rate of 100 Hz.
Keywords: Quantum Dot; Quantum Cryptography; Polarisation Entanglement; Delpoyed Fiber; Telecom