Study Of Reconciliation For CVQKD Using Coherent States Based On LDPC Codes

Continuous-variable quantum key distribution (CVQKD) is a protocol using the amplitude and phase quadrature of the quantum state of light to implement QKD, which can have access to standard telecom components and wavelengths compared with discrete-variable QKD. Thanks to probing easily and implementing robustly so it has extensive application perspective.Based on the basic principles of quantum mechanics, this thesis makes a detail introduction of coherent CVQKD such as basic principles and experiment scheme. Furthermore, phase control and balance homodyne detection technology are analyzed respectively with the phase-locking algorithm and the implementation of heterodyne detection in the QKD experimental protocol, and the performance of phase-locking is demonstrated comparing the results between different methods.After CVQKD's introduction, this thesis makes a focus on the classical data post-processing of CVQKD, which mainly consists of data reconciliation and privacy amplification detailed in the paper respectively. In particular, the application of the low-density parity-check codes(LDPC) is specifically investigated in data reconciliation, such as the generalization of implementation from the channel coding of classical LDPC codes to correlated distributed source coding, the study from the principle of coding and decoding of LDPC codes to the ideology or essence of correcting errors, the design from the algorithm to the implementation program of reconciliation applying LDPC codes, and the verification of the performance and principle of correcting errors. Sequentially, the perfect correcting errors efficiency in the reconciliation is demonstrated by the simulation of LDPC codes.At last, we simply describe the procedure and implementation of the data reconciliation with the demonstration of the software, which makes a foundation to the future soft-&-hardware design of the data post-processing of CVQKD.