  Combined with one-time pad encryption scheme, quantum key distribution
guarantees the unconditional security of communication in theory. However,
error correction and privacy amplification in the post-processing phase of
quantum key distribution result in high time delay, which limits the final
secret key generation rate and the practicability of quantum key distribution
systems. To alleviate this limitation, this paper proposes an efficient
post-processing algorithm based on polar codes for quantum key distribution. In
this algorithm, by analyzing the channel capacity of the main channel and the
wiretap channel respectively under the Wyner's wiretap channel model, we design
a codeword structure of polar codes, so that the error correction and privacy
amplification could be completed synchronously in a single step. Through
combining error correction and privacy amplification into one single step, this
efficient post-processing algorithm reduces complexity of the system and lower
the post-processing delay. Besides, the reliable and secure communicaiton
conditions for this algorithm has been given in this paper. Simulation results
show that this post-processing algorithm satisfies the reliable and secure
communication conditions well.
