綜觀近5至10年的科技研革，從大數據[1]，緊接雲端資源[2]，所帶來的資訊安全議題，及這幾年的AI人工智慧[3]等等……，皆顯示傳統的測量及運算方式，已逐漸無法滿足人類的需求，近年來隨著google、IBM等科技巨頭陸續發表的量子產品，亦顯示「量子」科技的發展正如火如荼；然談到光的非古典量子態，最基本的莫過於數態和壓縮態，在現今各個量子應用上，單光子光源也都是項重大議題，故本研究欲利用腔增強自發參量下轉換，非線性晶體為週期性極化鈮酸鋰，及先驅機制來製備單光子光源，以探討其特性並期做更多應用。

Looking at the scientific revolution of these 5 to 10 years. We can find the shortcomings and insufficient of traditional computing from the application of big data, cloud system, and AI (Artificial Intelligence) etc. And with the market share importance from the technology magnates such as google, IBM, also showing us the development of “quantum technology” is in full swing. However, touch upon the non-classical quantum states of light. Nothing is more important than number state and squeezed state. Nowadays in quantum applications, single photon light source is always a big issue. Therefore, this research proposes to produce a heralded single photon source by cavity-enhanced spontaneous parametric down conversion, which nonlinear crystal is PPLN (Periodically Poled LiNbO_3), for using in quantum states understanding and quantum application.

第一章 、緒論.....................................................6
第二章 、理論.....................................................7
2-1 二階諧波產生 (Second Harmonic Generation, SHG)................7
2-1-1泵浦(Pump)光與倍頻光.........................................7
2-1-2有效非線性係數(Effective nonlinear parameter, d_eff).........10
2-1-3 非線性轉換效率(Efficiency, η_SHG)...........................15
2-1-4 准相位匹配(Quasi-phase-matching)...........................17
2-2 自發參量下轉換(Spontaneous Parametric Down Conversion, SPDC)..19
2-2-1 訊號(signal)、閒置(idler)，與泵浦(pump)光....................19
2-2-3 光子對產生率(Photon-pair production rate)...................22
2-2-3 波長、折射率與溫度..........................................23
2-3 單光子光源(Single photon light source).......................25
2-3-1 二階自相關聯函數(Second-order auto-correlation function, g^(2))..........................................................25
2-3-2 先驅單光子源(Heralded Single Photon Source, HSPS)...........29
2-3-3 洪-歐-孟德爾干涉(Hong-Ou-Mandel Interference, HOMI).........34
第三章 、文獻回顧.................................................37
第四章 、方法與結果...............................................41
4-1 研究架構.....................................................41
4-2 SPDC頻譜(spectrum of SPDC)...................................44
4-3 符合窗與濾窗(Coincidence & Filtering window)..................47
4-3-1符合窗(Coincidence window, τ_c).............................47
4-3-2 濾窗(Filtering window, τ_f)................................50
4-4 先驅率(Heralding rate).......................................55
4-5 先驅單光子源之二階自相關聯函數：g_ssi^((2)).....................58
4-6 頻譜亮度(Spectral Brightness, SB)............................61
4-7 洪-歐-孟德爾干涉(Hong-Ou-Mandel Interference, HOMI)...........64
第五章 、結論.....................................................67
參考文獻.........................................................70
附錄、系統儀器規格................................................74
I) Laser, crystal, and cavity................................74
II) Detection – The spec of our SNSPD........................76
III) SINGLE PHOTON COUNTING – THE SPEC OF QUTAG..............78
IV) STABILIZATION – POUND-DREVER-HALL, PDH..................79

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