Security analysis of continuous variable quantum key distribution based on entangled states with biased correlations

Einstein-Podolsky-Rosen (EPR) entangled states can significantly enhance the secret key rate and secure distance of continuous-variable quantum key distribution (CV-QKD). In practical imperfections always exist in the preparation of two-mode squeezing (entangled states), which present an asymmetrical variance for the two quadratures. The imperfections induced by the bias effect of the entangled states are commonly treated as part of the untrusted channel to decrease the performance of the system. Here, we theoretically quantify the influence of bias effect on the secret key rate and secure distance, and propose a solution of generating unbiased entangled states protocol. The results demonstrated that the unbiased entangled states protocol guarantees the longest secure distance and highest key rate compared to that of coherent and biased entangled states. (C) 2021 Optical Society of America under the terms of the OSA Open Access Publishing Agreement