Towards metropolitan free-space quantum networks

This paper advocates for entanglement-based free-space quantum networks as a practical alternative to fiber-based systems for metropolitan applications. A deployable free-space QKD system was developed and tested, achieving secure key rates of up to 5.7 kbps over a 1.7-km link, even reaching 2.5 kbps in direct sunlight. Extrapolations suggest kbps key rates are feasible for 10-km distances and multi-user scenarios, positioning free-space networks as a viable solution for metropolitan quantum communication.

Andrej Kržič, Sakshi Sharma, Christopher Spiess, Uday Chandrashekara, Sebastian Töpfer, Gregor Sauer, Luis Javier González-Martín del Campo, Teresa Kopf, Stefan Petscharnig, Thomas Grafenauer, Roland Lieger, Bernhard Ömer, Christoph Pacher, René Berlich, Thomas Peschel, Christoph Damm, Stefan Risse, Matthias Goy, Daniel Rieländer, Andreas Tünnermann, Fabian Steinlechner