Postselection strategies for continuous-variable quantum key distribution protocols based on error probability distribution
Phys. Rev. Applied 26, 044013 – Published 5 October, 2026
DOI: https://doi.org/10.1103/5wd9-j761
Abstract
Discrete-modulation continuous-variable quantum key distribution (DM-CVQKD) has attracted considerable interest due to its compatibility with coherent optical communication systems and low hardware complexity. In DM-CVQKD protocols, postselection is widely employed as an effective technique to enhance protocol performance. However, conventional postselection schemes rely on fixed-shape regions in phase space, which fail to adapt to variations in the bit error rate (BER) distribution. In this work, we introduce a BER contour postselection (BER-PS) method, in which postselection regions are constructed according to the BER distribution, such that samples are selected based on their associated error probability. Under the trusted detector noise model, we perform a numerical security analysis of the BER-PS method in the asymptotic regime. Simulation results demonstrate that the BER-PS method consistently outperforms conventional fixed-shape postselection schemes in terms of achievable secret key rates. We perform experimental verification to confirm the feasibility of the BER-PS method. The results demonstrate that our scheme yields effective performance gains in both theoretical analysis and experimental measurements.
