This paper presents an experimental realization of a continuous-variable quantum key distribution (QKD) protocol using propagating displaced squeezed microwave states. Superconducting parametric devices are used for state generation and single-shot quadrature detection. Unconditional security is demonstrated, improved by adding trusted noise. Feasibility is shown for secure microwave quantum communication using current technology in both open-air (up to ~80 m) and cryogenic (over 1000 m) conditions.

Florian Fesquet, Fabian Kronowetter, Michael Renger, Wun Kwan Yam, Simon Gandorfer, Kunihiro Inomata, Yasunobu Nakamura, Achim Marx, Rudolf Gross, Kirill G. Fedorov