Scalable Implementation of Temporal and Phase Encoding QKD with Phase-Randomized States

Quantum key distribution (QKD), that is, exchanging cryptographic keys encoded in quantum particles exploiting the laws of quantum physics, is already a reality in our society. Current implementations are based on attenuated laser technique, a practical replacement of single photons which requires a random phase for each quantum state in order to achieve the highest level of security. In particular, the time-bin and phase encoding techniques are mainly exploiting laser in gain-switching modes combined with asymmetric interferometers or multiple laser sources in a master-slave configuration, which present limitations in terms of stability and scalability. In this work, a novel scheme for implementing a reconfigurable and scalable QKD transmitter based on the time-bin encoding protocol with a decoy-state method employing phase-randomized weak coherent states is proposed and demonstrated. The scheme is tested and validated up to 26 dB-attenuation channel using standard single-photon detectors working in the telecom wavelength range. Quantum key distribution (QKD), exchanging cryptographic keys exploiting the laws of quantum physics, is already a reality in our society. Current implementations are based on attenuated lasers, which present limitations in terms of stability and scalability. This work demonstrates a novel scheme for implementing a reconfigurable and scalable QKD transmitter based on time-bin encoding and decoy-state employing phase-randomized weak states.image