单空间模连续变量相干光通信方案的实验研究

发布时间：2018-07-25 12:57

【摘要】：连续变量量子密钥分配是一种新的量子通信技术,相比于离散变量量子密钥分配,其具有成本低、不需要单光子源、操作方便等优点。但若采用流行的M-Z干涉仪构建传输光路,信号光路和本振光路往往难以同步,需要采用较复杂的算法和压电器来补偿。由于压电器存在迟滞和蠕变性,算法存在置后性,因此,将导致连续变量量子密钥分配速度慢、过程复杂等缺点。本课题采用单空间模连续变量相干光通信的实验方案,用Stokes参量作为操作量,信号光与本振光在同一束光中传输,同步性强,提高了通信的稳定性。本文主要内容如下：首先,以Stokes参量作为可操作量构建单空间模连续变量相干光通信系统,分析各部分光路结构。重点介绍LiNbO3晶体的电光效应,SU(2)结构的编码与解码原理。通过MATLAB仿真确定驱动电源的电压范围,为硬件驱动及控制电路设计提供依据。通过USB传送系统将编码数据给PC,解码后的偏振光由零差检测和电信号采集传送给PC。通过二次采样、滤波、提取等操作,实现通信信号的后处理和误码分析。其次,设计了ARM+DSP硬件开发系统,ARM作为主控部分,利用其片上外设SPI口完成与DSP通信及与驱动电源的数据传输任务。利用Cortex M3内核完成快速中断响应及协调事务功能。发挥DSP的强大计算能力,执行禁忌算法,寻找电压值的最优解,从而能减轻了硬件电路和晶体的负载,提高了分发速率。根据硬件电路结构的特点,采用抢占式多任务实时操作系统,由ARM内部的SysTick定时器实现操作系统中的时钟节拍以高精度速率运行,实现多任务快速切换。根据系统中消息队列功能,在DSP和ARM中建立编码和电压的环型队列存储结构,解决算法时间不确定带来的非周期性存储障碍。最后根据设计的方案,在光学平台上搭建硬件环境,在不同光强下,测量随机偏振态。由LabVIEW软件对发送数据和接收数据进行分析,先是滤波除去噪声,再由设计的“动态窗口”解决激光漂移问题。通过分析测量数据可知,所设计的ARM+DSP硬件开发系统,能够实现测量基的随机选择,测量稳定性好、操作容易的特点,达到设计目标,可用于连续变量量子密钥分配。
[Abstract]:Continuous variable quantum key distribution is a new quantum communication technology. Compared with discrete variable quantum key distribution, it has the advantages of low cost, no need of single photon source and easy operation. However, if the popular M-Z interferometer is used to construct the transmission optical path, it is difficult to synchronize the signal optical path and the local oscillator optical path, so it is necessary to use a more complex algorithm and voltage apparatus to compensate. Because of the hysteresis and creep of the piezoelectric apparatus and the postposition of the algorithm, the quantum key distribution speed of continuous variables will be slow and the process will be complicated. In this paper, the experiment scheme of single space mode continuous variable coherent optical communication is adopted, and the Stokes parameter is used as the operating quantity. The signal light and the local oscillator light are transmitted in the same beam, and the synchronization is strong, and the communication stability is improved. The main contents of this paper are as follows: firstly, the coherent optical communication system with single space mode continuous variable is constructed using Stokes parameters as operable variables, and various optical circuit structures are analyzed. The encoding and decoding principle of Su (2) structure of LiNbO3 crystal is introduced in detail. The voltage range of the driving power supply is determined by MATLAB simulation, which provides the basis for the design of the hardware drive and control circuit. The encoded data is transmitted to PCs by USB transmission system, and the decoded polarized light is transmitted to PCs by homodyne detection and electrical signal acquisition. Through secondary sampling, filtering, extraction and other operations, the communication signal post-processing and error analysis. Secondly, the ARM DSP hardware development system, arm, is designed as the main control part. The communication with DSP and the data transmission with the driving power supply are accomplished by using the SPI port on the chip. The Cortex M 3 kernel is used to complete the function of fast interrupt response and transaction coordination. By using the powerful computing power of DSP, the Tabu algorithm is executed to find the optimal solution of the voltage value, which can reduce the load of the hardware circuit and crystal and improve the distribution rate. According to the characteristics of the hardware circuit structure, the preemptive multitask real-time operating system is adopted. The clock beat in the operating system runs at a high precision rate by the SysTick timer inside the ARM, and the multi-task fast switching is realized. According to the message queue function in the system, the ring queue storage structure of coding and voltage is established in DSP and ARM, which solves the aperiodic storage obstacle caused by the uncertainty of algorithm time. Finally, according to the designed scheme, the hardware environment is built on the optical platform, and the random polarization states are measured under different light intensities. The transmission and receiving data are analyzed by LabVIEW software. Firstly, the noise is removed by filtering, then the problem of laser drift is solved by the designed "dynamic window". By analyzing the measurement data, we can see that the ARM DSP hardware development system designed can realize the random selection of measurement bases, good stability of measurement, easy operation, achieve the design goal, and can be used for quantum key distribution of continuous variables.
【学位授予单位】：福州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TN929.1

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