Design And Analysis Of Quantum Receivers In Space Optical Communication System

Nowadays the receivers frequently used in most laser communication systems are classical receivers (direct detection, homodyne and heterodyne receivers). These receivers’theoretical bases are classical electrodynamics and classical detection and estimation theory, and their performance limits in terms of symbol error rates are called standard quantum limits (SQLs). Existing studies have shown that, starting from quantum electrodynamics and quantum detection and estimation theory, quantum receivers with symbol error rates smaller than SQLs can be designed. The performance limits of quantum receivers are referred to as Helstrom limits, and Helstrom limits are significantly lower than SQLs. Since Helstrom limits are obtained in the late of1960s, physical implementations of quantum receivers to surpass SQLs and achieve Helstrom limits have attracted many researchers. For a long time, limited by technology development level, the researches on quantum receivers’physical implementations move slowly. There were no breakthrough progresses in this field until recent years. Nevertheless, current researches on quantum receivers still remain in the experimental demonstration phase. In order to use quantum receivers in practical laser communication systems, there are many issues to be further studied.In the thesis, from classical to quantum, we first review the development history of information technology and receivers in the laser communication systems. Then we introduce the theoretical bases of laser communication systems receiver designs. On the basis of these contents, we deeply investigate some issues closely related to the practical use of quantum receivers in space optical communication systems. And the main achievements are listed as follows.(1) For binary modulation, based on the realistic model of the optimal displacement quantum receiver, we obtain the practical model of the Partitioned-Interval Detection quantum receiver including the effects of the sub-unity quantum efficiency and the dark counts of single-photon detectors (SPDs), as well as the loss and the mode mismatch of beam splitters. By using this model, we analyze each of the above four non-ideal factors’impacts on the symbol error rates of the Partitioned-Interval Detection quantum receiver. Finally, through comparing the simulation results with different partition strategies, we give the basic principles of choosing partition strategy in practice.(2) For multiple modulation, first, we obtain the practical probability model of the M-ary PSK adaptive measurements quantum receiver with on-off SPDs considering the above four non-ideal factors of each device. Based on this model, the separate impacts of the above four non-ideal factors on the symbol error rate of the receiver for QPSK and8-PSK modulation are analyzed through Monte Carlo simulation. After that, we point out by using photon number resolving detectors (PNRDs) instead of on-off SPDs, the impacts of mode mismatch can be suppressed effectively. Then the impacts of PNR capability of the PNRDs on the symbol error rates of the receiver are investigated. On the basis of the above studies, we give a detailed analysis of the symbol error rates of the16-QAM adaptive measurements quantum receiver. In order to surpass the SQL with less partitions using on-off SPDs, inspired by QPSK classic-quantum hybrid receiver,16-QAM classic-quantum hybrid receiver are designed.(3) For space optical communication systems using quantum receivers, we analyze the impacts of atmospheric turbulences on the receiver symbol error rates. First, we review the modeling methods of atmospheric turbulences effects. Then combined with the symbol error rates of quantum receivers without considering the atmospheric turbulences effects, an integral equation which can be used to analyze the impacts of atmospheric turbulences on the performances of quantum receivers is presented. As an example, we obtain the symbol error rates of QPSK adaptive measurements quantum receiver with on-off SPDs considering the atmospheric turbulences effects.