Free Space Decoy-state Quantum Key Distribution Implementation

摘要

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 communicatio ns. 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 alignme nt 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%.