Research On Improving Efficiency Of Quantum Key Distribution

Quantum Key Distribution is one of the important applications of quantum infor mation science. The issue of improving the efficiency and security of QKD is hot topic in quantum cryptography. This paper mainly focused on improving the final key rate and enhancing the security of practical QKD implementation. Our contributions included following three parts:1. A more efficient protocol combining the decoy state method and biased scheme was proposed. In this new scheme, biased basis choice was applied to the preparation and measurement process, thus it not only improved the final key rate but also simplified the system and reduced the random number consumption. We also used a rigorous method to upper bound the phase error rate of the single-photon components of signal states.2. We studied the statistical fluctuations caused by finite resources in practical QKD implementation and presented a new analysis method based on Chernoff-bound. Comparing to standard error analysis, the new method could weaken the needed assumption and obtain more accurate results.3. The information reconciliation process of QKD was researched in this paper. We proposed an improved row-combining method which could be used in information reconciliation. The new row-combining method could change the code rate of LDPC codes adaptively. The codes generated by this way possessed good girth property. We also presented an improved LBP algorithm which helped to improve convergence speed and reduce calculation amount. This paper put forward a new information reconciliation protocol based on these two new algorithms. The new protocol utilized Q uasi-C yclic LDPC codes that were beneficial to storage and hardware implementation.