高效率糾纏光子源之研究

Abstract

(1) 類光束狀多光子糾纏態 在最近成果中，我們在國立交通大學的實驗室，成功以類光束狀光子產生偏振特 性的糾纏光子對，這是首次在台灣所建立具有糾纏態的光源。 傳統建構偏振糾纏光子對的實驗，會使用濾波片選取特定波長的光子進行實驗， 卻導致光子產生率的降低。我們建立的類光束狀光子對可以完全產生糾纏態，比起傳 統的實驗，光子對被應用的效率可以大幅提升。 本計畫預計以現有類光束光子對的經驗與技術，產生有偏振特性的多光子糾纏源。 (2) 波導產生糾纏光子對 我們已經成功在實驗室中，將兩對類光束光子對進行干涉實驗；以及用二對二光 纖使光子糾纏，得到偏振糾纏光子對。 比較兩種實驗，發現第二種方法更容易最佳化，並由結果發現，這兩種方式都可 以產生高效率的糾纏光子對。然而，光子在二對二光纖中傳遞時，偏振方向會被改變， 造成糾纏度的降低。因此，在第二個計畫，我們提出以波導取代二對二光纖的構想， 以解決此影響。 本實驗團隊有超快雷射加工的經驗，波導的設計與製造可以相互討論，以利未來 更進一步的研究與發展。

(1) Beam-like photon pair generation for entangled multi-photon pair Recently, we have succeeded to generate beam-like photon pair entangled in polarization in National Chiao-Tung University. This is the first light source for entangled photon pair generation in Taiwan. The result was reported in the following papers which we recently published (refs. [1] and [2]). A traditional system for polarization entangled photon pair generation should apply a spatial filter to select the photon pairs entangled in polarization. However, the spatial filter causes a large loss in photon pair production rate. The beam-like photon pair generation system can generate entangled photon pair with high efficiency compared with traditional entangled photon pair generation systems because the photon pairs generated in our new photon pair generation system are all entangled in polarization In this project, we are planning to generate multi-photon pair entangled in polarization taking advantage of the high efficiency in the photon pair generation. (2) New scheme to entangle photon pairs using a wave-guide We have utilized two methods to entangle the beam-like photon pairs generated in our system. In the first scheme, we have overlapped optical path of beam-like photon pairs (reported in ref [1]). In the second scheme, we have used a 2x2 fiber to entangle the beam-like photon pairs (reported in ref. [2]). Our second scheme is much simpler than our first scheme in its alignment, and the obtained quality of the entanglement was almost comparable in both of the two schemes. This second scheme was found to be useful method to generate entangled photon pairs in simple setup. However, during transmission through the 2x2 fiber, polarization can be deformed (rotated) contaminating the quality of the entanglement. As a second topic of this project, we are planning to apply a recent methodology of a wave-guide in place of the 2x2 fiber. We expect that we can entangle the photon pairs without contaminating the quality of the entanglement. Our group has been working on the study of laser marking as seen in the publication (ref. [3]), therefore we are planning to produce a wave-guide whose structure is optimized to entangle the photon pair with high quality of the entanglement. [1] “Beamlike photon-pair generation for two-photon interference and polarization entanglement”, Hsin-Pin Lo, Atsushi Yabushita, Chih-Wei Luo, Pochung, Chen, Takayoshi Kobayashi, Phys. Rev. A, 83, 022343 (2011) [2] “Beamlike photon pairs entangled by a 2x2 fiber”, H.P. Lo, A. Yabushita, C.W. Luo, P.C. Chen, T. Kobayashi, Phys. Rev. A, 84, 022301 (2011) [3] “The fabrication of ZnSe nanoparticles by femtosecond laser ablation technique”, Hsuan-I Wang, C.W. Luo, master thesis (2011) (500 words)