Realization of intermodal fiber/free-space quantum key distribution networks
Francesco Vedovato, Francesco Picciariello, Ilektra Karakosta Amarantidou, Davide Scalcon, Marco Avesani, Edoardo Rossi, Alessia Scriminich, Giulio Foletto, Matteo Padovan, Alessandro Lorenzetto, Federico Berra, Luca Calderaro, Florian Kutschera, Martin Achleitner, Hannes Hübel, Giuseppe Vallone, Paolo Villoresi · 2023
Intermodal quantum key distribution (IM-QKD) enables the integration of fiber networks and free-space connections, which can be ground-to-ground links or involve satellite nodes in orbit. IM-QKD permits to extend the reach of free-space links without trusting any additional node, but this requires to efficiently couple the free-space signal into a single-mode fiber (SMF). We present the implementation of different IM-QKD networks realized in Padova and Vienna, exploiting km-long deployed fibers and free-space channels up to 620 meters. We show that such an intermodal scheme is compatible with both in-house QKD systems and commercially available solutions exploiting polarization encoding at 1550 nm. Remarkably, we realized different QKD tests in daylight and also in rainy conditions.