【作者】 白云飞；

【导师】 张俊香； 郜江瑞；

【作者基本信息】 山西大学 ， 光学， 2011， 博士

【摘要】 单光子态是一种非常重要的非经典光场,它在量子光学基础研究、量子保密通讯和量子计算等领域中发挥着至关重要的作用。常见的制备单光子态的方法主要有量子点、色心、衰减脉冲和自发参量下转换。与其他方法相比,自发参量下转换有着独特的优势。该过程利用二阶非线性相互作用,将泵浦光子转换成一对高度关联的光子对,只要测到其中之一,就可以确认其孪生光子的存在。这样,我们就可以在不破坏单光子的前提下确认单光子的存在,从而弥补了原子相干介质和衰减脉冲等方法的不足。此外,由于参量下转换过程产生的光子对在多个维度上都具备纠缠特性,可以用来制备各种纠缠光源以满足不同的应用。因此,自发参量下转换过程及其制备的条件单光子源无论在理论还是实验上都得到了广泛且深入的发展。单光子源的制备、传输与测量以及对单光子的量子操控是量子信息科学领域中的一个前沿课题,它不仅能够丰富人们对微观世界的认识,加深对量子物理基本原理的理解,还同时为量子通信与量子计算过程的实现提供了坚实的物理基础。有关单光子量子效应的研究对促进量子网络的发展尤为重要,已经渗透到了从光源产生到量子信息的调制与解调,再到信息分发及频率转换等量子网络的各个环节,并且还将在其他量子领域逐渐发挥其潜在的巨大作用。本文的主要工作是围绕单光子源的制备、传输和测量展开的,其核心内容包含以下几个方面：1.总结了实验上产生单光子态的各种物理模型,对每种方法的利弊进行了分析并给出了自发参量下转换过程产生单光子所具有的独特优势；在此基础上,实验研究了利用脉冲光学谐振腔增强了单光子产生率,得到了一个更加明亮的单光子源。2.设计并研究了可以用来测量弱脉冲信号的平衡零拍探测系统,分析了该系统的各项性能指标,并且对弱相干光脉冲进行了时域内正交分量信息的测量。3.阐述了有关单光子的各种量子干涉效应,用经典物理工具描述了单光子与多光子干涉的物理原理,给出了一个普适的解并具体分析了在单光子态平衡零拍测量过程中的应用。4.基丁HOM干涉原理,利用时间反演的HOM过程实验上实现了一个确定性量子分束器,用一个普通的分束器将完全简并的光子对以较高的概率进行空间上的分离；被分束脉冲的时间精度从皮秒量级提高到了飞秒量级。5.提出了谐振腔内的量子态频率转换方案,通过引入保真度、信号传输系数和能量转换效率的概念定义了频率转换效率并找到了量子态的完全频率转换条件,同时分析了信号光振幅、泵浦参量以及内腔损耗等因素对频率转换效率的影响。在这些研究工作中,属于创新性的工作有以下几点：1.利用超短脉冲光学谐振腔,在不改变脉冲超快重复率和频率梳结构的情况下,极大地提高了二阶非线性过程的参量增益,获得了一个明亮的单光子源。2.根据时间反演的HOM干涉原理,完成了确定性量子分束系统的设计与测量,可以将飞秒脉宽量级的、完全简并的双光子从空间上彻底分离。3.提出了基于谐振腔的量子态频率上、下转换模型。与单次穿过方案中的频率转换模型相比,该方案更容易提高量子态频率转换效率,对具体的实验具有一定的指导意义。该模型适合于弱光场尤其是单光子态的频率转换。更多还原

【Abstract】 Single photon state is a very essential non-classical light field, which playing a more and more important role in quantum optics foundation, quantum cryptography and quantum computer. The commonly used methods to generate the single photon state include of quantum dots, color center, decay pulse and spontaneous parametric down conversion (SPDC). Compare to the other methods, the SPDC have unique advantages. Based on the second-order nonlinear interaction, this process converts a pump photon into entangled photon pair, once one of SPDC photon was detected, the existence of its twin photon could be verified. Thus we can obtain a single photon without any destruction, and compensate the other methods in this respect. Besides, considering the SPDC photon pair has entangled properties in multiple dimensions, this resource can be used to prepare various entangled source. So both the SPDC process and the single photon state have been deeply developed in theoretical and experimental aspects.The preparation, transmission, measurement and manipulation of single photon source are advanced topics in quantum information domain. It not only enriches the knowledge to microscopic world and reinforces comprehension to quantum mechanics fundamental, but also provide a solid foundation to quantum communication and quantum computation. Specially, the researches involved single photon quantum effects are important to quantum network. It has access to every part of network such as the preparation of optical source, modulation, demodulation and distribution of information, and frequency conversion. A potential influence will be gradually manifest in other quantum field.In this thesis, we introduce our works mainly around the preparation, transmission and measurement of single photon source. The key parts contain following aspects: 1. Summarize various physical models to generate the single photon state, analyze the advantages and disadvantages, and give the unique superiority of SPDC; design a resonant cavity for pulse experimentally based on the SPDC process and obtain a brighter single photon source.2. Design and investigate the balanced homodyne detection system for measurement of weak pulse, analyze the performance and parameters, and construct the quadrature components of weak coherent light in time domain.3. Explain the quantum interference effect related single photon state, analyze the interference fundamental principle between single photon and multiphoton by utilizing of the classical physical tool, and give the universal resolution and applications in balanced homodyne detection of single photon state.4. Based on the HOM principle, realize a deterministic quantum splitter experimentally by use of the time-reserved HOM process, make the degenerated twin photons separate from each other completely only with the help of a common beam splitter. The order of magnitude of pulse width that is split had been increased from ps to fs.5. Proposed an intracavity frequency conversion scheme of quantum state, define the conversion efficiency through the concept of fidelity and signal transfer coefficient, find out the complete conversion condition. Meanwhile, the influence of signal amplitude, pump parameter and cavity losses to frequency conversion efficiency are also analyzed.The creative works are listed as follows:1. By utilizing a low-lost ultra-short pulse resonant cavity, increased the parametric gain tremendously while keeping its repetition rate and comb structure, obtain a brighter single photon source.2. According to the time-reserved HOM interference principle, design and verify a deterministic quantum splitter experimentally using only a common beam splitter and separate the completely degenerated photon pair of fs pulse width with a higher efficiency.3. Propose an intracavity model of quantum frequency up and down-conversion, it can increase the conversion efficiency easier than the travelling-wave scheme and would give the instructive help to specific experiment. This frequency conversion model is suitable for the weak field especially single photon state.更多还原