Free space decoy-state quantum key distribution implementation

LÓPEZ GRANDE, I.H.; LAROTONDA, M.A.; MAGNONI, A.G.

Optica Pura y Aplicada

Sociedad Espanola de Optica

Año: 2018 vol. 50 p. 187 - 192

0030-3917

In this work we introduce a complete Quantum Key Distribution device that implements a decoy-state protocol [1]. Qubits are coded in the polarization state of weak optical pulses, produced by infrared LEDs [2]. The link between Transmission (Alice) and Reception (Bob) stages is open air, which is the preferred channel to eventually through low-orbit satellites establish quantum communications. Both terminals are placed on different rooms, separated by approximately 8 meters. In order to compensate misalignments produced by small mechanic displacements or atmospheric thermal gradients, the system implements a closed-loop for automatic alignment based on a counter-propagating laser, a servo-actuated mirror and a CMOS image sensor. The apparatus runs in an autonomous way, and in the above described conditions it is able to generate raw cryptographic key at a rate of 185 bits/s, with a QBER of 6.15%.