【作者】 李涛；

【导师】 张俊香； 郜江瑞；

【作者基本信息】 山西大学 ， 物理电子学， 2009， 硕士

【摘要】 量子信息科学是量子物理与信息科学相结合而形成的新兴交叉学科,它被认为是最具有应用潜力的发展学科之一,因此备受研究者关注。原子与光场相互作用作为量子信息科学的一个重要研究方向,是实现量子开关,量子逻辑门,量子存储等的天键。腔量子电动力学就是阐述腔场与原子相互作用的现象,早期人们对腔量子电动力学的研究发现,在原子和腔发生强耦合过程中,引起原子和腔之间不断的能量变换,原子不断的将腔模中的光子吸收然后释放,在原子能级间形成拉比振荡,从而产生了真空拉比分裂。过去人们普遍认为真空拉比分裂是腔量子电动力学系统中,光与原子强耦合作用下的量子现象;鉴于腔量子电动力学实验的复杂性,近年来,有关原子团或原子系综在腔中的各种量子现象的研究引起很大的关注。最近,美国研究组报道了利用三能级热原子系综与腔耦合,不仅可以观察到真空拉比分裂,同时也可以观察到原子相干效应引起的暗态透射谱,从而将腔量子电动力学的一些量子现象扩展到普通的光与原子相互作用研究范围。该论文进一步研究了四能级N型系统中的真空拉比分裂和原子相干效应现象,从而在腔与四能级原子耦合系统中观察到真空拉比分裂和双暗态效应,这一研究将会对量子开光,光谱测量以及激光稳频等具有应用前景。该论文通过两束激光(耦合光和控制光)与腔内四能级原子系统耦合后,对耦合腔的腔透射谱进行测量,表明谱线出现四个独立的透射峰,即双真空拉比边带和双内腔暗态,并同时验证了可以通过第三束控制光实现对真空拉比分裂的增强效应。与此同时讨论了真空拉比频率和控制光对模分裂和暗态的影响,说明其双拉比边带和双暗态的位置和大小可以通过真空拉比频率和控制光的拉比频率进行调控。当控制光拉比频率足够大时,双暗态与拉比边带位置重合,此时两个拉比边带的分裂不仅得到增强,其边带峰的强度也明显强于同等条件下的三能级系统,这一结果说明,通过提高第三束耦合光的功率可以实现真空拉比分裂的增强,为常温条件下,真空拉比分裂的观测提供了一种简便方法。总之,该论文讨论了多能级原子系统与多光束光场相互作用情况下真空拉比分裂与内腔暗态的量子现象,预测了得以增强的真空拉比分裂,为将来进一步研究原子与腔相互作用的量子行为奠定了基础。更多还原

【Abstract】 Quantum information science, as a emerging cross-disciplinary of quantum physics and information science, is considered one of the most potential applications of the developing disciplines and receives so much attention to the researchers. The atom-cavity interaction is one of the most important research directions of quantum information science and the key of the realization of quantum switch, quantum logical gate, quantum storage. Cavity QED is the early phenomenon of interaction between atoms and the cavity field. As is shown in the early research of cavity quantum electrodynamics, there is ongoing energy exchange between atom and cavity field in the strong-coupling regime. Thereby the vacuum Rabi splitting comes into being due to the Rabi oscillation: the atom cyclically absorbs photons and re-emits them. In the past, it is universally acknowledged that the vacuum Rabi splitting is the quantum phenomenon of Cavity QED in the atom-cavity strong-coupling regime. In view of the complexity of the CQED, some researches on quantum phenomenon related with atoms or atomic ensembles in a cavity have raised a lot of concern in recent years. Lately, the American groups report three-level hot-atom-regime the vacuum Rabi splitting and intra-cavity dark state similar to the EIT in a cavity. Thus some quantum phenomena expand from Cavity QED to the general interaction of light and atoms. This paper further study of the vacuum Rabi splitting phenomenon and atomic coherence effects in the N-type four-level system and could observe the vacuum Rabi splitting and double dark states in the four-level atom-cavity system. The study has application prospects for quantum light switch, spectral measurements and laser frequency stabilization.In this framework, we calculate the transmission spectrum of four-level atom-cavity system by making use of two laser beam (the coupling beam and the controlling beam) coupled to the four-level system and manifest that we can observe simultaneously four separate transmission peaks- twoRabi sidebands and double darks states. Meanwhile we prove that the enhanced vacuum Rabi splitting could be achieved by the third controlling laser beam. We also study the influence of the vacuum Rabi frequency and the Rabi frequency of controlling beam on the Rabi splitting and dark states, indicating that we could manipulate the position and intensity of the Rabi splitting and dark states by changing of the vacuum Rabi frequency and the Rabi frequency of controlling beam. We find that when the Rabi frequency of the controlling beam is large enough, the double dark states and the Rabi sidebands have superposition. The splitting of two Rabi sidebands enhances and their intensity is obviously larger than that of three-level system in the same conditions. This results show that we could get the enhanced vacuum Rabi splitting by increasing the power of the controlling beam. The study provides a convenient method to observe the evident vacuum Rabi splitting in the normal temperature condition.In a word, we discuss the quantum phenomena of the vacuum Rabi splitting and intra-cavity dark states in the interaction between multi-level atom and multi-beam field and forecast the enhanced vacuum Rabi splitting in the experiment. We lay the foundation of accurately predicting the quantum behavior of the interaction between atom and cavity in the future.更多还原