Ilektra Karakosta Amarantidou

Intermodal quantum key distribution (QKD) provides a fundamental interface for scalable quantum networks. Nevertheless, long-distance implementations are typically compromised by turbulence-induced aberrations, which decrease coupling efficiency into single-mode fiber. Here, we report a real-time intermodal QKD field trial over an 18 km free-space link, connecting a remote terminal to an urban optical ground station. By utilizing an adaptive optics system for high-order aberration correction, we achieved efficient single-mode fiber coupling and a secure key rate of 200 bit/s using room-temperature detectors. Furthermore, we validate a turbulence-based coupling model that provides practical design guidelines for future interoperable quantum architectures.