Spatially coupled LDPC-BCH codes in quantum secure direct communications
WANG Ping1, SUN Zhen1, YIN Liuguo2,3,4, LU Jianhua1,2
1. Department of Electronic Engineering, Tsinghua University, Beijing 100084, China; 2. School of Information Science and Technology, Tsinghua University, Beijing 100084, China; 3. Beijing National Research Center for Information Science and Technology, Beijing, 100084, China; 4. Key Laboratory of EDA, Research Institute of Tsinghua University in Shenzhen, Shenzhen, 518057, China
Abstract：Quantum secure direct communication systems are limited by high erasure probabilities and low receiving probabilities due to the high light source losses in the optical elements and optical fibers. A channel mitigation method based on spatially coupled LDPC-BCH codes is presented here to ensure reliable information transformations in quantum secure direct communication systems to resolve the problems of low-rate and Shannon limit-approaching code designs. Spatially coupled LDPC-BCH codes are constructed by coupling multiple identical block LDPC-BCH codes with edge spreading. The extrinsic information transfer functions of the spatially coupled LDPC-BCH code are analyzed to derive the decoding thresholds for the code ensembles. Simulations show that the spatially coupled LDPC-BCH codes have decoding thresholds closer to the Shannon limit with lower bit error rates than block LDPC-BCH codes. The spatially coupled LDPC-BCH code channel mitigation scheme has a transmitting efficiency of 0.001 and a bit error rate less than 10-6 when the channel receiving probability is set at 0.4%.
王平, 孙臻, 殷柳国, 陆建华. 用于量子安全直接通信的空间耦合LDPC-BCH码[J]. 清华大学学报（自然科学版）, 2019, 59(9): 737-743.
WANG Ping, SUN Zhen, YIN Liuguo, LU Jianhua. Spatially coupled LDPC-BCH codes in quantum secure direct communications. Journal of Tsinghua University(Science and Technology), 2019, 59(9): 737-743.
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