Andrea Tomaello

Feasibility of satellite quantum key distribution

In this paper, we present a novel analysis of the feasibility of quantum key distribution between a LEO satellite and a ground station. First of all, we study signal propagation through a turbulent atmosphere for uplinks and downlinks, discussing the contribution of beam spreading and beam wandering. Then we introduce a model for the background noise of the channel during night-time and day-time, calculating the signal-to-noise ratio for different configurations. We also discuss the expected error-rate due to imperfect polarization compensation in the channel. Finally, we calculate the expected key generation rate of a secure key for different configurations (uplink, downlink) and for different protocols (BB84 with and without decoy states, entanglement-based Ekert91 protocol).

Study of the Quantum Channel between Earth and Space for Satellite Quantum Communications

In this work there are studied the conditions for the effective quantum communications between a terminal on Earth and the other onboard of an orbiter. The quantum key distribution between a LEO satellite and a ground station is studied in particular. The effect of the propagation over long distances as well as the background during day or night is modeled, compared and discussed in the context of key generation and exchange.

Feasibility Analysis for Quantum Key Distribution between a LEO Satellite and Earth

Terrestrial QKD channels can connect two links with a maximum distance of few hundred kilometres. In the case of fibre links, this is due to the signal attenuation in the fibre; in the case of free-space link the losses are due to atmospheric turbulence and absorption. Free-space optical terminals exploiting satellite-based relays are the only resource that can enable global scale quantum key distribution, since single photon propagation is for the main part in vacuum with no turbulence or absorption, and just a small part of the path is through the atmosphere. Several proof-of-principle experiments have been carried out recently: among these the feasibility of single-photon exchange between a satellite and an optical ground station was demonstrated in 2008 [1].

Intersatellite quantum communication feasibility study

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.

Turbulent single-photon propagation in the Canary optical link

The role of turbulence for Quantum Communications (QC) has been investigated in a 143 km-long link. The analysis of the received signal temporal domain indicate how to exploit constructively its effects in the case of QC along very long free-space links as well satellite links. Novel applications with relevant background noise may be envisaged.

Experimental Studies Toward the Quantum Communications with Orbiting Terminals

Realization of Quantum Communications in Space requires a deep understanding of issues including link-budget, turbulence mitigation and single-photon terminal synchro-nization. Here we report on supporting novel experiments on very long-distance links and modeling.

Long range beam propagation for quantum communications

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.

Experimental Study of Free-space Beam Propagation for Single-photon Quantum Communications

We report on the study the propagation of a laser beam over a 144 free-space link. We report on the losses of the channel, the temporal scintillation of the intensity and, by attenuating the beam, the statistic of arrival of single photons.

The space as frontier for global quantum communications

The sharing of quantum states among ground and orbiting terminal may be considered as feasible according to present optical technologies. The paradigm shift that Quantum Communications represent vs. classical counterpart allows to envisage the application of global cryptographic key distribution as well as the extension to Space of quantum technologies.

Long range beam propagation for single-photon communications

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.