强耦合原子—腔系统的单原子实时探测与俘获

发布时间：2018-05-13 23:00

本文选题：微光学腔 + 铯原子输运　；参考：《山西大学》2016年博士论文

【摘要】：原子的辐射特性不仅由其内部结构决定,而且也会受到外界环境的影响。通过改变原子周围电磁场的模式分布密度,原子与光的相互作用可以得到明显增强。例如将单个原子置于仅有一个模式的光学腔中,就可以实现单原子与单模场之间的相互作用；当其耦合强度远远超过原子与外场模式的作用时,就形成原子-腔系统典型的能谱结构,即系统处于腔量子电动力学(Cavity Quantum electrodynamics, Cavity QED)的强耦合区域。这样的系统是研究单原子-腔场相互作用的理想系统,用于基础量子物理问题的研究和量子信息处理及量子网络的构建等研究领域,而在光学腔内操控单个原子的内外态是实现以上目标的必要条件。该论文主要基于强耦合的腔QED实验系统所开展。在实验中通过铯原子团自由下落方式输运原子到微腔的腔模内,从而实现单原子与腔模的强耦合作用以及其腔内俘获。通过蒙特卡洛方法模拟并结合实验采集的单原子穿越腔模的信号,不仅可以确定磁光阱中冷原子的温度,而且可以优化实验参数；其次基于强耦合的原子-腔系统的单原子“显微镜”来观测单原子与微腔的不同横模的强耦合作用；并可记录单原子穿越不同横模的运动轨迹,对原子位置的测量精度达到亚微米量级；此外,通过大量原子到达腔模的时刻得到磁光阱的原子束的统计性质,在不同初始温度下观察到了热原子束的聚束效应；接着为了对单原子在腔内进行相干操控和提高其与腔模的作用时间,实验上搭建了两维双色偶极阱,实现了单原子在轴向由魔数波长所构成的驻波偶极阱内的态不敏感的冷却与俘获,并通过腔冷却机制使原子在腔内亮阱中驻留时间达到大约7ms；再者在理论和实验上系统的研究了基于纳米光纤实现对原子的俘获；最后,理论上研究了基于光学腔实现突破经典极限测量的方案,可以指导实验进一步提高原子位置的测量精度。在这些研究工作中,创新性的工作有以下几点：1.建立了基于原子自由下落来输运原子到微光学腔的物理过程,并通过蒙特卡罗方法对实验整个过程进行了模拟,模拟结果与实验数据符合很好,并提出一种新的测量温度的方法,进一步将模型用于实验室新一代光学腔的设计,对新腔参数的设计具有指导意义。2.基于光学微腔作为单原子显微镜,通过腔的透射谱观测到原子与微腔不同模式的强耦合,对单原子位置的测量精度达到了亚微米量级；并研究了磁光阱中冷原子的统计特性,从磁光阱下落到光学腔的原子束满足玻色-爱因斯坦统计分布,其关联特性呈典型的“聚束”效应。3.利用远失谐的魔数波长构建的腔内驻波偶极阱,实现了单原子在腔内的长时间俘获,并借助腔致冷却来进一步提高原子在腔内的驻留时间,实现了态不敏感的腔内单原子冷却与俘获以及实时观测。4.研究用锥形的纳米光纤构建偶极阱来俘获原子,为操控原子开辟了一条新的道路,对于量子通讯的应用有重要的意义,其优势在于扩展性强、传输效率高以及小型化。5.研究了基于光学腔,结合非经典光(压缩真空态)与非高斯测量(光子数可以分辨的探测和宇称探测)实现突破经典极限的测量方案,通过两者相结合实现了超分辨与超灵敏的探测,使其成为一种有潜力的量子策略来实现增强量子计量：并在实验上尝试使用压缩真空态光场与冷原子结合来实现更高的精度地测量原子运动或者得到系统的一些新的非线性现象。
[Abstract]:The radiation characteristics of an atom are not only determined by its internal structure, but also influenced by the external environment. By changing the mode distribution density of the electromagnetic field around the atom, the interaction between atoms and light can be significantly enhanced. For example, the single atom and single mode field can be realized by placing a single atom in only one mode of optical cavity. When the coupling strength is far more than the effect of the atom and the field mode, it forms the typical spectral structure of the atomic cavity system, that is, the strong coupling region of the cavity quantum electrodynamics (Cavity Quantum electrodynamics, Cavity QED). Such a system is an ideal system for the study of the interaction of single atom cavity field. The study of fundamental quantum physics and quantum information processing and the construction of quantum networks, and the control of the internal and external states of a single atom in the optical cavity is a necessary condition for the realization of the above targets. This paper is mainly based on a strongly coupled cavity QED experimental system. The atoms are transported to the cavity mode of the microcavity to realize the strong coupling of the single atom with the cavity mode and the capture in the cavity. The Monte Carlo method is used to simulate and combine the experimental data of the single atom through the cavity mode, not only to determine the temperature of the cold atom in the magneto-optical trap, but also to optimize the experimental parameters. Secondly, the atom is based on the strong coupling atom. The single atom "microscope" of the cavity system is used to observe the strong coupling effect of the single atom and the different transverse modes of the microcavity, and can record the trajectory of the single atom passing through the different transverse modes, and the measurement precision of the atomic position reaches the order of submicron. In addition, the statistical properties of the atom beam of the magneto-optical trap are obtained by a large number of atoms arriving at the cavity mode. The bunching effect of the hot atomic beam is observed at different initial temperatures. Then, in order to manipulate the single atom in the cavity and improve the time of its interaction with the cavity mode, a two dimensional double chromatic dipole trap has been built, and the insensitive cooling and capture of the single atom in the stationary wave dipole trap formed by the wavelength of the magic number is realized. By the cavity cooling mechanism, the retention time of the atom in the cavity of the cavity is about 7ms. Furthermore, in theory and experiment, the capture of atoms based on nano optical fiber is studied systematically. Finally, the scheme based on the optical cavity to achieve the breakthrough of the classical limit measurement is theoretically studied, which can guide the experiment to further improve the atomic position. In these research work, the innovative work has the following points: 1. the physical process of the atom to the micro optical cavity is established based on the atom free falling, and the whole process of the experiment is simulated by Monte Carlo method. The simulation results are in good agreement with the experimental data, and a new measurement temperature is proposed. Method, the model is further used in the design of a new generation optical cavity in the laboratory. The design of the new cavity parameters is useful for the design of the new cavity parameters..2. based on the optical microcavity is used as a single atom microscope, the strong coupling of the different modes between the atom and the microcavity is observed through the transmission spectrum of the cavity, and the measurement precision of the single atom position is reached to the sub micron order. The statistical characteristics of the cold atoms in a magneto-optical trap, the atomic beam falling from the magneto-optical trap to the optical cavity satisfies the Bose Einstein statistical distribution, and its correlation characteristic is a typical "bunching" effect.3. using the far detuned magic number wavelength to build a standing wave dipole trap, which realizes the long time capture of the single atom in the cavity, and the cavity induced cooling is used. One step improves the retention time of the atom in the cavity, realizes the insensitive intracavity single atom cooling and capture, and the real-time observation of the.4. study using the conical nanofiber to build the dipole trap to capture the atom. It opens a new road for the manipulation of the atom, which is of great significance to the application of the quantum communication. Its advantages lie in the strong extensibility and transmission. High efficiency and miniaturized.5. research based on optical cavity, combined with non classical light (compressed vacuum state) and non Gauss measurement (photon number distinguishable detection and parity detection) to achieve a breakthrough in the classical limit of the measurement scheme, through the combination of both the realization of super-resolution and hypersensitivity detection, making it a potential quantum strategy. To achieve enhanced quantum metrology, the experiment is to try to combine the compressed vacuum state light field with the cold atom to achieve higher accuracy in measuring the motion of the atom or to obtain some new nonlinear phenomena of the system.

【学位授予单位】：山西大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O413.2;O562

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