In the frame of the Spanish GEO QKD project, which aims to develop the first quantum key distribution (QKD) system from geostationary orbit, Thales Alenia Space and its partners have achieved the transmission of QKD signals (individual photons) in free space, covering a distance of 140 km through turbulent atmosphere. This is an essential step to validate the GEO QKD system in a real environment before its deployment in space.
