Continuous-variable quantum key distribution (CV-QKD) enables secure communication over standard telecom infrastructure, yet its scaling is stalled by bulky, discrete optical hardware. We address this bottleneck by demonstrating a real-time CV-QKD system driven by a chip-scale hybrid transmitter built from commercial telecom components. By integrating a micro-optic external-cavity laser with a monolithic photonic integrated IQ modulator, we provide high performance, enabling secret-key generation over 102 km of optical fiber, while reducing the size of the optics by 95%. Moreover, real-time operation overcomes the offline post-processing bottlenecks of experimental setups. This work bridges laboratory demonstrations and field-deployable technology, with a scalable architecture for cost-effective quantum networks.
@article{arxiv.2603.13483,
title = {A Chip-Scale Transmitter Module for Real-Time Continuous-Variable QKD},
author = {Igor Servello and Martin Hauer and Moritz Baier and Emmeran Sollner and Peter Gleißner and Sebastian Randel and Ulrich Eismann and Emanuel Eichhammer and Imran Khan},
journal= {arXiv preprint arXiv:2603.13483},
year = {2026}
}