Enhancement of key generation rate in QKD systems using dual branch PNR detectors.

What we believe to be a new architecture based on dual-branch photon-number-resolving (DB-PNR) detectors for the receiver in the hybrid quantum key distribution (QKD) is introduced. DB-PNR scheme empowers the receiver to detect both quadratures of the coherent state simultaneously. Our results show that using DB-PNR detectors, the key generation rate (KGR) is almost doubled as compared to homodyne detection which detects only one quadrature at a time. The mutual information is enhanced by around 0.85 bits/symbol using DB-PNR as compared to heterodyne detection. DB-PNR is also found to outperform the heterodyne detection against Eve's individual and collective attacks. PNR-based detection schemes require less local oscillator (LO) power compared to homodyne/heterodyne detection schemes and thereby, the power efficiency of the receiver is enhanced.