Entanglement-based quantum key distribution using three satellites

Laszlo Bacsardi, Zsolt Kis

LB: Institute of Informatics and Economics, University of Sopron, Hungary
ZSK: MTA Wigner Research Centre for Physics, Budapest, Hungary

Quantum key distribution (QKD) provides secret keys which can be used for symmetrical cryptographic protocols. Although commercial applications of QKD technology are already available, currently direct fiber-based QKD links cannot reach distances beyond a few hundred kilometers due to the optical losses on the fiber. Long-distance QKD networks may be feasible using quantum repeaters, but such devices are not ready for operation. But free-space links offers many possibilities. Using satellite links as free-space quantum channels, global free-space QKD network can be provided.

In recent years, we have started to analyze the properties of the Earth-satellite quantum communication by simulating a global, satellite-based quantum key distribution network. We have proposed an entanglement-based QKD satellite network which consists of three satellites. One satellite serves as the source of entanglement, the two others work as mirrors to increase the coverage. This solution utilizes the satellite as a trusted node. While the moving satellites generate and reflect the entangled pairs of photons, the basis states of the received qubits may be rotated in reference to what the basis states were on the generating satellite. The angular velocity of this rotation depends on the location of the ground station, the attributes of the mirror and the generator. The aim is that, we want to be able to calculate the received qubit's angle of rotation knowing the attributes of the ground station and the satellites.

The research was supported by the Hungarian Scientific Research Fund – OTKA PD-112529.

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