  Information reconciliation (IR), which corrects the errors in the sifted
keys, directly determines the secure key rate and the link distance of quantum
key distribution (QKD) systems. In this article, we propose an appending
information reconciliation (AIR) scheme based on polar codes, which achieves
high efficiency and ultra-low failure probability simultaneously, by gradually
disclosing the bit values of the polarized channels with high error
probability. The experimental results show that the efficiency of the proposed
AIR scheme is closer to the Shannon limit, compared with the state-of-the-art
implemented polar codes-based IR schemes, with the overall failure probability
around 1E-8, especially when performed with smaller block sizes. Moreover, the
efficiency of the proposed AIR scheme is 1.046, when the block size is 1 Gb and
the quantum bit error rate of 0.02. Therefore, the proposed AIR scheme can
further eradicate the performance gap between theory and implementation for QKD
systems.
