Interfering-or-not-interfering quantum key distribution with advantage distillation

Abstract: Interfering-or-not-interfering quantum key distribution (INI-QKD) is an innovative protocol whose performance surpasses existing twin-field protocol variants. In this study, we introduce an additional step of advantage distillation (AD) after the quantum communication phase to further enhance its performance. Through the AD the raw key is partitioned into small blocks of bits to identify highly correlated bit pairs. We numerically compute the optimal partitioning for different realistic conditions. Our results show that by employing the advantage distillation the transmission distance is significantly increased and thus can potentially improve the secret key rate of INI-QKD. This in particular is most prominent in the presence of high polarization misalignment error rates and considerable phase mismatch, all without altering the experimental setup of the protocol.