鉀的雷德堡原子光譜

Laser Spectroscopy of Potassium Rydberg Atoms

張劭宇(Shao-Yu Chang)

指導教授 ： 劉怡維

國立清華大學/理學院/物理學系/碩士(2018年)

摘要

德堡原子有很多特殊的性質吸引許多科學家研究，如大偶極矩。在量子電腦的領域中，強偶極交互作用是量子邏輯閘的重要組成部分。異核雷德堡分子是量子讀取中的一個重要問題，它是如何分辨受控粒子和目標粒子的一個解決方案。因此，研究不同物種間的雷德堡交互作用力和產生異核雷德堡分子預計是未來量子資訊技術發展的重要方向。我們的研究方向為鉀-銣原子雷德堡互作用力與產生鉀銣異核雷德堡分子。本篇論文中冷鉀的雷德堡原子第一次被完成，作為上述兩項目標之基礎。首先在熱原子實驗中，我們研究雷德堡-雙共振光泵浦架構(Double Resonance Optical Pumping)。他類似雷德堡-電磁誘發透明架構，但有明顯光泵浦效應與跟高的偵測光強度。我們的實驗系統是基於倒梯型架構和室溫鉀原子。整個系統包含兩個外腔式半導體雷射，一雷射波長為四百零四奈米，共振於鉀 4S→5P 能階。另一雷射為近紅外光雷射共振於中間態與雷德堡態。為了耦合中間態與雷德堡態，我們使用錐形放大器
將紅光強度提高至一瓦。藉由光學布洛方程，我們建立了雷德堡-雙共振光泵浦架構的理論模型。為了驗證理論模型，我們提供偵測光吸收光譜與螢光光譜來佐證。最後我們利用磁光陷阱產生兩百微克耳文冷鉀原子並利磁光陷阱損失訊號觀察到四個雷德堡光譜包括 70S 和 68D。本篇論文是第一個演示了冷鉀的雷德堡原子。

關鍵字

鉀原子 ； 雷德堡原子 ； 雙共振光泵浦架構 ； 外腔式半導體雷射 ； 量子邏輯閘

並列摘要

Rydberg atoms exhibit several exaggerated properties such as large dipole moments which are interesting to fundamental physics and quantum technology application. Strong dipole-dipole interaction is important in quantum gate which is an essential key to the quantum computer. Heteronuclear is also an important issue in quantum readout, which is one of the solutions for distinguishing controlled and target atoms. Hence, to study the inter species Rydberg interaction and to produce heteronuclear Rydberg molecules are expected to be important for future quantum information technique development. Our research directs to the Rydberg interaction of K-Rb and to produce KRb heteronuclear Rydberg molecule. In this thesis, as the initialization of such a research, we report the first realization of the cold potassium Rydberg atoms. Firstly, in the hot cell experiment, we study Rydberg-Double Resonance Optical Pumping (DROP) scheme which is similar to EIT but with open channel and higher probe power. Our experimental system is based on an inverted ladder type scheme and room temperature potassium atoms. The laser system consist of two homemade external-cavity-diode-laser (ECDL). One of the laser wavelength is 404 nm, which is resonance to potassium 4S → 5P transition. And a nearinfrared laser system NIR laser, to couple the intermediated state(5P) and Rydberg states, is composed of an ECDL and a tapered amplifier to reach 1 W. By optical Bloch equation, we have developed a theoretical model for the Rydberg-DROP scheme. To verify the theoretical model, we have demonstrated good agreements the model and experimental result in the Rydberg-DROP spectrum and the fluorescence spectrum. Finally, with a magneto-optical trap to produce a cold potassium of 200 µK, we observed four Rydberg transitions, including 70S and 68D using trap loss signals. The cold Rydberg potassium is therefore demonstrated.

並列關鍵字

Potassium atom ； Rydberg atom ； DROP scheme ； external-cavity-diode-laser ； quantum gate

參考文獻

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