本論文研究冷銣原子鑽石型能級結構中的單光子量子頻率轉換，並將其應用於預示式原子雙光子波包的通訊波段轉換。原子系統產生的窄頻光子具有長相干時間與量子記憶相容性，但其波長通常與低損耗光纖通訊波段不匹配，因此需要高效率且低失真的量子頻率轉換介面。本研究建立鑽石型原子系綜頻率轉換的理論模型，並在冷原子實驗中將雙 Λ 型自發四波混頻所產生之 795 nm 預報探測光轉換至 1367 nm 通訊波段。實驗結果顯示，當 2.5 MHz 預報光子頻譜位於轉換器高效率響應區域內時，訊號光轉換效率可達 79.4(2.6)%，且維持明確的時間關聯波包；對於較寬的 17.4 MHz 輸入頻寬，轉換效率約為 55%，但主要時間波包仍大致保持。此結果顯示，有限轉換頻寬主要造成光子數損失，而非顯著的時間模態失真。本研究證明，透過適當的頻譜匹配，冷原子鑽石型系統可實現高效率、低失真的預報單光子通訊波段轉換，為窄頻原子量子光源與光纖量子通訊網路之間建立可行介面。

This thesis investigates single-photon quantum frequency conversion in a diamond-type cold rubidium atomic ensemble and its application to the telecom conversion of heralded atomic biphoton wavepackets. Narrowband photons generated from atomic systems are compatible with quantum memories but are usually not matched to low-loss telecom fiber channels, making efficient and low-distortion frequency conversion essential. In this work, a theoretical model for diamond-type atomic frequency conversion is developed, and a cold-atom experiment is implemented to convert the 795-nm heralded probe photon generated by double-Λ spontaneous four-wave mixing into a 1367-nm telecom-band photon. When a 2.5-MHz heralded-photon spectrum is placed within the high-efficiency region of the converter response, a signal conversion efficiency of 79.4(2.6)% is achieved while maintaining a well-defined temporal correlation waveform. For a broader 17.4-MHz input bandwidth, the conversion efficiency is reduced to approximately 55%, whereas the dominant temporal waveform remains largely preserved. This behavior shows that finite conversion bandwidth mainly causes photon loss rather than significant temporal-mode distortion. These results demonstrate that, with proper spectral matching, a diamond-type cold-atom system can provide efficient and low-distortion telecom conversion of heralded single photons, establishing a feasible interface between narrowband atomic photon sources and fiber-based quantum communication networks.

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