Research On LDPC Codes In Post Processing Of Quantum Key Distribution

With the rapid improvement in computer performance and development inalgorithm, especially the successful advancement of the techniques of quantumcomputing, it brings serious threats to the classical encryption system since its securityis based on the computational complexity. The security of Quantum key distribution(QKD) is based on the fundamental theorem of quantum mechanics, which have aphysical absolute security feature, can effectively overcome the shortcomings of currentcomputing complexity based encryption system. Information reconciliation is one of thekey technologies to ensure the consistency of the shared key that Alice and Bob jointlyowned by correcting the key error due to the inherent noise of the quantum channel andeavesdropping and other factors led to quantum key distribution. In the recent few years,LDPC codes based quantum information coordination gradually become a cutting-edgetechnology in the post-processing of the quantum key distribution, which has attractedextensive attention.In this paper, we performed an in-depth study on the randomly constructingalgorithm and experimental platform for LPDC based Quantum Key Distribution. Ourmajor research efforts can be summarized as follows,1. We introduced the development course of the information reconciliation, andclassified the current information reconciliation; discussed existing randomconstruction algorithms of LDPC codes, summarized the characteristics of existingrandom construction algorithms of LDPC codes, and then analyzed the advantagesand disadvantages of existing random construction.2. According to the disadvantage that current algorithms lack of the ability of GlobalOptimization, we proposed a construction algorithm of LDPC codes based ongenetic algorithm-GAS. We designed populations, genetic operators, fitnessfunction etc. The GAS algorithm has advantages of global optimization andmulti-information search.3. We designed to implemented information-oriented reconciliation testing platform–CLIP, According to the requirement of QKD system. CLIP is composed ofemulation of quantum channel, encoding module etc.4. We tested and analyzed the performance of GAS in CLIP. The result shows that theperformance of LDPC codes constructed by GAS is much better than the classicGallager algorithm. We also studied the characteristics of LDPC codes， which is agood foundation for further study.