Quantum key distribution (QKD) is an important branch of quantum information science as it provides unconditional security to classical communications. For QKD research, a central issue is to improve the secure key rate (SKR) and transmission distance of a practical QKD system. To address this issue, we focus on reducing the reconciliation leakage without compromising security. Through eliminating the part of leaked information that has already been considered before reconciliation, this paper presents a novel approach for estimating reconciliation leakage more accurately to break through the limits of conventional approaches. The general SKR formulas of two typical QKD protocols are then derived based on our approach. Simulation results showed that our proposed approach efficiently improves the SKR at any distance as well as the maximum transmission distance under practical experimental parameters.
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