【作者】 王琴；

【导师】 郭光灿； 黄运锋；

【作者基本信息】 中国科学技术大学 ， 光学， 2006， 博士

【摘要】 二十世纪初发展起来的量子力学是继相对论之后人们对客观物质世界的本质认识的一大进步。而量子信息学则将信息学和量子力学成功地结合起来，考虑在量子效应明显的各种信息处理系统中的各种问题，从而将信息科学的发展带入了一个新天地。在量子信息学中，信息的存储、表示、提取都离不开量子态(量子力学用于描述物质系统状态的数学工具)及其演化过程。而量子纠缠态无疑是各种各样的量子态中最为重要的一类了，它在量子信息学的两大主要领域—量子通信和量子计算中都有着广泛而重要的应用；另外，对于量子纠缠态性质的研究也使得我们可以更深刻地理解量子力学的观点。实验上量子纠缠的产生有很多种方法，例如在腔QED、离子阱、核磁共振(NMR)系统、半导体材料、自发参量下转换等系统中都已经制备出了量子纠缠态，这些纠缠态有原子之间的纠缠，离子之间的纠缠，也有电荷之间的纠缠，而在自发参量下转换系统中则是光子之间的纠缠。由于实验技术的限制，这些方法都有种种缺陷与不完善。相比之下，参量下转换的方法是最为简单易行的方法，也是人们最为常用的一种方法。利用晶体的非线性性质，通过自发参量下转换产生光子纠缠对具有产生效率高、容易操纵等优点，在量子操控技术的发展中具有巨大的应用前景。这也是本人将纠缠光子对的制备、收集、干涉与应用的实验研究作为博士论文的主要原因。本人在实验和理论上主要取得了以下主要成果： Ⅰ．高亮度纠缠光子对的获得 目前，如何利用自发参量下转换技术获得更高亮度的纠缠光子对已经成为量子信息科学领域一个亟待解决的问题。无论是对于Ⅰ型与Ⅱ型的位相匹配，还是准位相匹配，均已有许多不同的理论模型与实验方案被提出，我们结合已有的理论模型与自己的实验经验，制备出了接近国际领先水平的高亮度的纠缠光子对。这种纠缠源的获得为我们下一步进行量子通信、多光子纠缠操纵等方面的实验提供了必不可少的条件。 Ⅱ．高干涉可见度的HONG-OU-MANDEL干涉 Hong-Ou-Mandel(HOM)干涉仪由于具有稳定性好、偶阶色散取消等各种优点，在量子信息及其相关领域具有广泛应用，也是纠缠纯化、纠缠浓缩、量子隐形传送、Bell基测量等各类实验中必不可少的装置。我们经过长时间的摸索与经验积累，大大提高了搭建HOM干涉仪的技术水平。无论是使用脉冲激光还是连续激光，对于Ⅰ型或Ⅱ型参量下转换，我们搭建的HOM干涉仪的干涉可见度均可大更多还原

【Abstract】 It is one of the greatest achievements for mankind to develop quantum mechanics besides the theory of relativity from the beginning of the twenty century, which makes people to understand the nature of the material world more deeply. Based on many problems with obvious quantum effects in information processing, it brings out the quantum information science which is also the combination of information science and quantum mechanics. As a result, it brings the science of information into a new world. In quantum information, the information storage, said and extraction all depend on quantum state and its evolution. (Quantum state is one of the mathematical tools in quantum mechanics to describe the material world.) Obviously, quantum entangled state is one kind of the most important states, because it has wide applications in both the fields of quantum communication and quantum computation. Moreover, the research on the property of quantum entangled states give us deeper understanding on the opinion of quantum mechanics. Up to now, there have been many quantum systems which can be used to produce entanglement, such as cavity-QED, trapped ions, NMR, semiconductor materials and spontaneous parametric down-conversion (SPDC) system. The entanglement they produced include the one between atom and atom, ion and ion, charge and charge et al., while for SPDC system, it is the one between photon and photon. Because of the technical constraints, each method has its shortcomings and imperfections, in contrast, SPDC process is the most important, most often and convenient method. By virtue of the characteristic of nonlinear optical crystal, the entangled state produced in this way has high entanglement degree and high fidelity, besides, it is easy to control. All these advantages make it the most promising candidate to be applied in quantum operations. The main results of the dissertation are as follows:I. Entangled photonpairs with high brightness Currently, how to obtain entangled photon pairs with higher brightness from SPDC process has become one of the most crucial problems limiting its further implementation in both quantum communication and quantum computation. Whether for type I and type II crystals, or for phase matching and quasi-phase matching conditions, there have been many theoretical models and experimental schemes. Based on them, we try to develop the brightness to a high level, which provides essential更多还原