The study of the free-space propagation of quantum correlations is necessary for any future application of
quantum communication aiming to connect two remote locations. Here we study the propagation of a coherent
laser beam over over 144 Km (between Tenerife and La Palma Islands of the Canary archipelagos). By attenuating
the beam we also studied the propagation at the single photon level. We investigated the statistic of arrival of
the incoming photons and the scintillation of the beam.
The shift in the Communication paradigm from the bit to the qubit is increasingly exploited in terrestrial long
range links and networks, with strong potentials in secure communications, quantum computing and metrology.
The space-to-ground quantum key distribution was also considered as feasible. A new different scenario for the
quantum communications is that of the intersatellite link. In this study we focus on the extension of intersatellite
communications into the quantum domain. The long distances involved and the fast relative motion are severe
constraints, partially compensated by the absence of beam degradation due to the propagation in the atmosphere
as well as the relatively low background noise level. We address the conception of the optical terminal and
the predicted performances in the case of constellations of LEO and MEO satellite including the quantum
communications and quantum teleportation.
In the perspective of the long range single-photon communications, we study in this work the propagation of
a single or twin optical beams in scale length of several tens to a few hundreds kilometres, introducing in the
experiment the collection of the whole beam combined to the measure of local irradiance. The experimental
models were realized in different localities of Italian Alps as well as between Tenerife and La Palma Islands of
the Canary archipelagos. The whole beam at the receiver was acquired and compared to models including the
local meteorological conditions.