Interfering-or-not-interfering quantum key distribution
Yang Yu, Wei Li, Le Wang, Shengmei Zhao · Physical Review A · 2024
Single-photon interference is the essential key for the recently well-known twin-field quantum key distribution (TF-QKD) to break the linear rate-distance limit and requires beams with identical polarizations. Inspired by this fact and aiming to improve the secret key rate, we propose a hybrid high-dimensional QKD named the interfering-or-not-interfering QKD (INI-QKD), in which both the polarization and phase degrees of freedom (DOFs) are adopted as information carriers. The protocol's security proof is analyzed based on entanglement distillation and three defined effective events, ${X}_{1}$, ${X}_{2}$, and ${X}_{3}$. The simulation shows that the ${X}_{1}$ event, from which only the phase information is extracted, exceeds TF-QKD's variants, while the ${X}_{2}$ and ${X}_{3}$ events, in which both types of information are decoded, can achieve twice the secret key rate as measurement-device-independent QKD (MDI-QKD). It is also proven that by adding the polarization DOF, INI-QKD obtains more resistance to phase mismatch than TF-QKD. Remarkably, these can all be achieved by simply altering the TF-QKD's measurement setup to that of MDI-QKD.