  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.
