二能階原子系統中單光子吸收之量子操控｜國立清華大學博碩士論文庫

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研究生：	陳奕丞 Chen, Yi-Cheng
論文名稱：	二能階原子系統中單光子吸收之量子操控 Quantum control of single-photon absorption in two-level atoms
指導教授：	褚志崧 Chuu, Chih-Sung
口試委員:	王立邦 Wang, Li-Bang 劉怡維 Liu, Yi-Wei
學位類別：	碩士 Master
系所名稱：	理學院 - 物理學系 Department of Physics
論文出版年：	2019
畢業學年度：	107
語文別：	中文
論文頁數：	45
中文關鍵詞：	量子通訊、量子資訊、相位調製、展頻技術、原子吸收
外文關鍵詞：	Quantum Communication, Quantum Information, Phase Modulation, Spread Spectrum Technology, Atomic Absorption
相關次數：	點閱：2 下載：0
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在古典通訊中，展頻技術可以有效增加資訊傳輸過程中的隱匿性與安全性，因此我們試著將此技術應用於量子通訊上，希望此方法同樣可以增加量子通訊的安全性。實驗上會以高頻的隨機訊號對 SPDC (spontaneous parametric down-conversion) 產生之窄頻單光子的波包進行相位調製，使其頻寬由 5.2 MHz 展至 10 GHz，讓單光子能免於被躍遷頻率同其頻率的原子吸收或偵測，達到隱形斗篷的效果，可增加光子在傳輸過程中的隱匿性，提升量子傳輸與量子密鑰分發之安全性。
未經調製的單光子在原子的吸收頻率上時會幾乎 100% 被吸收，實驗上我們將光子的頻寬從 2 GHz 展至 10 GHz，可讓吸收率從 70% 降至 30%，從此結果可了解，光子的頻寬越高能有越好的隱匿性，而提升安全性與傳輸效率。

In classical communication, spread spectrum technology is an effective way to improve the security in transmission process. We try to implement this technology in quantum communication as well. In our experiment, we have used synchronized high-speed electro- optic modulators to modulate the phase of resonant single photon and biphoton wave packets, which are generated from cavity enhanced SPDC (spontaneous parametric down- conversion) and broaden their bandwidths from 5.2 MHz to 10 GHz for avoiding photons being absorbed or detected by the atoms. The reduced absorption is like imposing an invisible cloak over a photon, improving the confidentiality during the transmission process in order to improve the security of quantum communication and key distribution.
In principle, atoms will absorb on-resonant narrowband (smaller than natural linewidth) single photons in our experiment. we broadened the bandwidth of the photon to a wide range between 2 10 GHz, with the absorption rate decreasing to 70 30% By these results, our work shows that, for transmitted photons, the higher the bandwidth, the higher the confidentiality.

摘要 ii
Abstract iii 
誌謝iv
目錄 v

一、 實驗背景與動機 1
1.1 古典通訊展頻 ................................................................. 1
1.2 量子通訊展頻 ................................................................. 3
1.3 研究簡介 ...................................................................... 4
二、 理論模擬 5
2.1 基本原理介紹 ................................................................. 5
2.2 相位調製 ...................................................................... 5
2.2.1 數學形式............................................................... 5
2.2.2 以單頻波之相位調製為例 ............................................. 6
2.3 展頻及壓縮.................................................................... 7
2.4 87Rb 原子氣體吸收............................................................ 9
2.4.1 展頻對吸收率的影響 .................................................. 9 2.4.2 原子吸收對頻譜還原之影響........................................... 11
三、 實驗架設 13
3.1 偽隨機訊號產生器 ............................................................ 13
3.2 電光調製器.................................................................... 14
3.3 高頻電訊號放大器 ............................................................ 15
3.4 電訊號相位延遲器 ............................................................ 17

3.5 光源製備 ...................................................................... 18
3.5.1 雷射光 ................................................................. 18
3.5.2 單光子 ................................................................. 18
四、 實驗方法與結果討論 24
4.1 雷射頻譜量測 ................................................................. 24
4.1.1 2 Gb/s 隨機訊號之相位調製.......................................... 25
4.1.2 10 Gb/s 隨機訊號之相位調製......................................... 28
4.2 經隨機相位調製後之 87Rb 原子吸收譜....................................... 29
4.3 單光子隨機相位調製對原子吸收之影響...................................... 31
4.4 雷射光隨機相位調製對原子吸收之影響...................................... 33
4.5 不同展頻頻寬對吸收率之影響................................................ 33
4.6 單光子頻譜壓縮............................................................... 34
4.7 雷射光頻譜壓縮............................................................... 36
4.8 誤差分析與模擬修正.......................................................... 37
五、 總結 40
參考文獻 41
附錄 A 法布立-培若干涉儀 42
附錄 B Etalon 干涉儀 45
                                

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