基于准相位匹配晶体的非经典光源的制备

发布时间：2018-01-05 11:41

本文关键词：基于准相位匹配晶体的非经典光源的制备　出处：《中国科学技术大学》2016年博士论文　论文类型：学位论文

【摘要】：无论是隐变量理论的否定还是EPR纠缠的证实,无论是量子秘钥分发还是量子隐形传态,非经典量子光源都是极重要的实验对象。本论文围绕光子和光子对的制备,开展了一系列的工作。基于准相位匹配PPKTP晶体的参量下转换过程,我们成功制备了红外通信波段高质量的偏振纠缠光源、腔增强高亮度的红外以及可见窄线宽光子对,此外,我们还在type-Ⅰ OPO中实现了模式可调的HG模窄线宽光子对。为了提供OPO腔的泵浦光源,我们还开展了低泵浦功率下的高效率倍频紫外激光研究。本论文的主要研究工作1.我们利用Sagnac干涉仪实现了偏振纠缠光子对的制备。我们用几种方法证明了产生的光子对具有很好的质量。双光子Hong-Ou-Mandel干涉具有95.3%±1.6%的干涉可见度,光子带宽2.4 nm。当光子的中心波长在20 nm内变化时,干涉可见度依然保持很高。双光子45°基Bell干涉曲线具有96.4%±2.0%的干涉可见度,而且不随温度和泵浦光功率变化。测量的CHS H(Clauser-Horne-S himony-Holt)不等式的S参数是2.63±0.08,在8a内违背不等式。对纠缠态的重构,我们得到的保真度为0.935±0.021。此外,产生的光子位于通信波段,而且是光纤输出,非常适合与光纤系统结合,用于光纤量子通信领域。2.我们实现了低泵浦功率下高效率397.5 nm倍频光的产生。我们工作的亮点是泵浦光(795 nm)的功率相对较低,仅110 mW,产生的蓝光有49 mW,足够去泵浦OPO腔产生光子对。产生的倍频光具有很好的空间模式,装置紧凑而稳定。和常见的商用倍频激光器相比,我们的倍频系统在一些场合更具有优势。例如对于调谐范围要求不高的地方如原子实验中,我们的系统可以省去昂贵复杂的激光放大器,直接用半导体激光器就能产生足够的倍频光。而且还可以利用半导体激光器的电流调制功能省去昂贵的电光调制器。此外,快速电流反馈也有助于提高系统的稳定性。3.我们实现了腔内Ⅱ型PPKTP晶体产生窄线宽光子对的实验。我们观察到多纵模光子对的互相关函数具有非常明显的梳状结构,信噪比超过100：1。在使用滤波腔滤出单纵模时,互相关函数的梳状结构消失,信噪比超过20：1,这证明了我们产生的是单纵模的窄线宽光子对。通过拟合,我们得到光子对的线宽为11.8 MHz,和原子的自然线宽在一个数量级,而且光子对的中心波长是780 nm,位于Rb原子跃迁的D2线,因此产生的光子可以与Rb原子系统结合,实现量子存储和量子中继。我们使用的泵浦光产生于单次通过倍频实验,功率只有几百μW。在今后我们计划将它换成腔内倍频方案,以便产生更强的泵浦光,这样可以增大单纵模光子对的产生率,提高量子通信和量子存储速率。4.我们实现了通信波段的窄带明亮光子源。我们使用了一个三共振的OPO腔,这样泵浦光也得到了增强,因而产生的光子对的亮度相比双共振情况有明显的提高。我们得到的光子带宽为8 MHz,相干时间为27.7 ns,亮度约为134±25s-1MHz-1mW-1。由于产生的光子位于通信波段,非常适合用于光纤系统中。如果将我们的光子源用高效率的全光纤器件实现,那将会成为量子通信里一个实用化的模块。5.我们希望能产生不同空间模式的光子对,我们对这一目标进行了初步尝试,我们先实现较容易的H G模光子的产生。我们将O P O腔锁定在高阶模上,就得到了H G模光子对。我们证明了产生的确实是非经典关联的光子对。两种情况下HG模式光子的带宽分别是11.4 MHz和20.8 MHz,与原子的自然线宽相当,波长位于780 nm附近,可以与原子系统相结合,实现高维量子存储。然后我们实现了一个模式简并消除腔,在这个腔中不同轨道角动量的光束共振频率不同,这样不同轨道角动量的光束之间不会由于简并而耦合,因此不需要非常理想的光学谐振腔就能使腔的本征模式是LG模。这为我们进一步实现直接产生窄带轨道角动量光子对奠定了基础。本论文的主要特色和创新点1.我们系统地研究了基于准相位匹配晶体的自发参量下转换过程。从单次通过形式到腔增强形式,从可见波段到红外波段,从直积态到偏振纠缠态,从基模光子到高阶空间模式光子。我们的工作全面而系统,涵盖了基于准相位匹配晶体的自发参量下转换过程的大部分情况。2.我们实现了通信波段偏振纠缠源的制备,纠缠光子具有很高的保真度和亮度,频谱特性很好,非常适用于量子通信领域。3.我们完成了单模窄线宽光子源的制备。从倍频光的产生,到多纵模光子对的制备,再到双共振单纵模光子对的制备,最后到三共振单纵模光子对的制备。我们的工作由浅入深,由易到难,系统而全面地研究了单纵模窄线宽光子源的制备。4.我们实现了多纵模窄线宽HG模光子对的直接产生。不同于以往将基模光子变换到高阶模的方法,我们产生光子对的方法可以保持很高的保真度,这在某些对保真度要求严格的场合是非常有用的。
[Abstract]:Whether it is the negation of the hidden variable theory or EPR entanglement confirmed that both quantum key distribution and quantum teleportation, quantum non classical light source is very important. The object of this dissertation focuses on the preparation of photon and photon, launched a series of work. The conversion process parameters of quasi phase matched PPKTP crystal under based on the success of our system of high quality light polarization entangled in infrared communication wavelengths by cavity enhanced infrared high brightness and narrow linewidth of visible photons, in addition, we still type- I realized in OPO HG mode tunable narrow linewidth of photon mode. In order to provide OPO cavity pump source, we also carry out efficient study on low frequency ultraviolet laser pump power. The main research work of this paper we use 1. Sagnac interferometer to achieve a system of polarization entangled photon. We prove that the light produced by several methods The quality is very good to have. The two photon Hong-Ou-Mandel interference visibility with 95.3% + 1.6%, 2.4 nm. bandwidth when the center wavelength of the photon photon changes within 20 nm when the interference visibility remained at very high. Two photon interference visibility 45 degrees based Bell interference curve with 96.4% + 2%, but not with temperature and the pump power changes. Measurement of CHS H (Clauser-Horne-S himony-Holt) S 2.63 + 0.08 parameter inequality is violated, inequality in 8A. The reconstruction of the entangled state, we obtain the fidelity of 0.935 + 0.021. in addition, the resulting photons in a communication band, and is very suitable for optical fiber output, combined with the optical fiber system for quantum communication field.2. we achieve low pump power efficiency of 397.5 nm frequency light. Our work is the highlight of the pump (795 nm) power is relatively low, only 110 mW, the blue Light is 49 mW, enough to produce photon pumped OPO cavity. The frequency doubling light has good spatial pattern, compact and stable. Compared with common commercial laser frequency system, we have an advantage more in some occasions. For example, the tuning range of the high requirements such as atomic experiments, we the system can save the expensive and complex laser amplifier, direct use of semiconductor laser can produce harmonic light enough. But also by the electro-optic modulator current modulated semiconductor laser without expensive function. In addition, the fast current feedback also helps to improve the stability of the.3. system we implemented cavity type II PPKTP crystal on the experiment Zhai Xiankuan photon. We observed the multi longitudinal mode of the photon correlation function has a comb like structure is very obvious, the signal-to-noise ratio of more than 100:1. in the use of filter cavity filter A single longitudinal mode, disappear comb structure cross-correlation function, the signal-to-noise ratio of more than 20:1, which proves that we are generating a single longitudinal mode and narrow linewidth photon pairs. By fitting, we get to the 11.8 MHz linewidth of photon and atom, the natural linewidth of an order of magnitude, and the center wavelength of the photon is 780 nm, is located in the transition of Rb D2 line, the resulting photons can be combined with the Rb atom system, quantum storage and quantum repeater. We use the pump to produce a single pass frequency doubling experiment, power is only a few hundred W. in the future we plan to change it into the introcavity frequency doubling, so that the pump have stronger, so they can produce on the rate of increase of single longitudinal mode photon, improve the quantum communication and quantum storage rate.4. we achieve narrowband communication band bright photon source. We use a three OPO cavity resonance, this kind of pump is Has been enhanced, compared to the brightness of the resulting double photon resonance is significantly improved. We obtained 8 photon bandwidth MHz, coherent time is 27.7 ns, the brightness is about 134 25s-1MHz-1mW-1. due to the photon in the communication band, is very suitable for the optical fiber system. If we use the photon source all fiber device of high-efficiency, it will become a practical quantum communication module.5. we hope to produce different spatial patterns of the photon, we conducted a preliminary attempt to achieve this goal, we first H G mode photon is easy to produce. We will O P O in the high order mode locking cavity that got H G mode photon pairs. We prove that the resulting is non classical correlated photon pairs. Two photon HG model under the condition of bandwidth are 11.4 MHz and 20.8 MHz, and a natural linewidth of atomic wave. Long at around 780 nm, can be combined with atomic system, realize high dimensional quantum storage. Then we implement a simple model and eliminate the cavity resonance frequency of different beam, different orbital angular momentum in the cavity, so that light beams of different orbital angular momentum is not due to degenerate and coupling, so there is no need to light the resonant cavity can be very ideal that intrinsic mode cavity is LG mode. It is further our implementation directly from the orbital angular momentum of photons on the narrow band of the foundation. The main features and innovations of the thesis 1. we systematically study the quasi phase matched crystal spontaneous parametric down conversion process based on enhanced form from a single. Through the form to the cavity, from visible to infrared wavelengths, from the product state of polarization entangled state, from the base to the high order mode photon space mode photon. Our work comprehensively and systematically, including based on quasi phase The conversion process of spontaneous parametric matching crystals under the most.2. we realized communication band polarization entangled source for the preparation of entangled photons with high fidelity and brightness, spectrum characteristic is very good, very suitable for the field of quantum communication.3. we finished the single-mode narrow linewidth light source. The preparation of the second harmonic wave generated from on the system, the multi longitudinal mode photon preparation, then to the system of double resonance single longitudinal mode photon preparation, and finally to the system of the three resonance single longitudinal mode photon. We work from the shallower to the deeper, from easy to difficult, systematic and comprehensive research of single longitudinal mode narrow linewidth photon source preparation.4. we implement a multi longitudinal mode narrow linewidth HG mode photon to produce the direct. Different from the fundamental mode of photonic transform to high order modes, we produce photon pairs can maintain high fidelity, which is in some non strict occasions on the fidelity It's often useful.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O43

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