Harald Weinfurter

The CubeSat mission QUBE aims to evaluate novel, miniaturized Quantum Key Distribution (QKD) building blocks in space including an optical downlink to an optical ground station. The mission will be launched in July 2024 and will provide important insights into new technology which potentially could form the backbone of a cost-effective satellite based QKD system on a global scale.

To establish a reliable Quantum Key Distribution (QKD) link from a satellite in low-earth orbit (LEO) to a ground station, a series of ground-to-ground tests are essential. These tests, varying in distance and objectives, are for fine-tuning both the sender and receiver systems to address the unique challenges of satellite communications. We detail the methods and outcomes of progressively complex QKD tests, for the different components of the satellite and ground station. The experiments clearly show the performance of the quantum optics payload as well as the capability of the QKD receiver and the optical ground station (OGS).

Error correction is an essential step in the classical post-processing of all quantum key distribution (QKD) protocols. We present error correction methods optimized for discrete variable (DV) QKD and make them freely available as an ongoing open-source project (github.com/XQP-Munich/LDPC4QKD). Our methods are based on irregular quasi-cyclic (QC) low density parity check (LDPC) codes and state-of-the-art rate adaption techniques.