Quantum optical ground station

The quantum optical ground station on Hafelekar is conceived as a platform for satellite-based quantum communication. At its core is a 1 m Ritchey–Chrétien telescope that provides the optical aperture required for long-distance free-space quantum links. The system is complemented by a polarization-entangled photon-pair source based on a Sagnac interferometer, delivering high-brightness and intrinsically phase-stable entanglement suitable for distribution to spaceborne platforms. The telescope system integrates high-accuracy tracking and beam stabilization to mitigate atmospheric turbulence and mechanical jitter. On the receiver side, a six-state polarization analyzer implemented with passive basis choice and avalanche photodiodes enables full state tomography and quantum key distribution protocols such as BB84 and BBM92. The overall architecture is designed for compatibility with upcoming quantum communication satellites, including QEYSSat and EAGLE-1, providing a testbed for secure global quantum networks and performance benchmarking under realistic atmospheric conditions