Realistic rate–distance limit of continuous-variable quantum key distribution
Xuyang Wang, Siyou Guo, Pu Wang, Wenyuan Liu, Yongmin Li · Optics Express · 2019
Continuous variable quantum key distribution (CV QKD) is a promising candidate for the deployment of quantum cryptography. At present, the longest distance is limited to ∼100 km at fiber-based quantum channel. We investigated in depth the realistic rate-distance limit (RDL) of CV QKD, considering reconciliation efficiency, finite-size effect, and realistic excess noise under collective attack. It is shown that the excess noise generated on Bob's side degrades significantly the transmission distance and we verify it in experiment. The improvement in RDL by reconciliation efficiency depends on the excess noise level, considerable increase of RDL by improving the reconciliation efficiency occurs only for relative large excess noises. A convergence modulation variance, useful in calculation simplification, is found. Furthermore, we restudy the finite-size analysis and eliminates a loophole arising from the Holevo-bound information monotonicity and a safe RDL is guaranteed. Based on the revised finite-size analysis, the optimum ratio determining the amount of data used for parameter estimation is analyzed.