Paolo Villoresi, University of Padua
Abstract
The paradigm shift that Quantum Communications represent vs. classical counterpart allows envisaging the application of global cryptographic key distribution as well as of other quantum technologies. The sharing of quantum states among ground and orbiting terminal may be considered as feasible according to present optical technologies. However, the extension of the Quantum Communications and Technologies to long distances, on the surface of the Earth as well as from the Earth to an orbiting terminal in Space, is influenced by difficulties, among which the moving terminals, the large losses, the effects on the optical propagation of the turbulent medium. Indeed, the quantum state that is prepared and sent at the transmitter side experiences a transformation in the spatial spectrum in addition to the vacuum diffraction, that requires strategies to be compensated. We addressed a series of experiments and modelling to address the relevant issues for the demonstration of the space quantum communications.
The study of optimal design of transmitter optics has been tested on very long links, including the 144 km path between Tenerife and La Palma Islands, and schemes for the aiming and the stabilization of transmission through turbulence has been devised.
The modelling of the quantum communications for the ground-to space and the intersatellite links has been analysed on the base of extensive calculations and the previous experience on the single-photon exchange with orbiting retroreflectors.