我們用波長1550nm線寬2MHz的古典光雷射做為光源，架設了測試DPS-QKD所需要的非等臂馬赫-曾德爾干涉儀，此架設比起一般的干涉儀多使用了兩面反射鏡將兩臂3m的光程差壓縮在小板子內。我們也測試了這個干涉儀的對比度及其穩定性，並打入一道反向進入干涉儀的雷射光搭配用Labview寫的自動回饋程式鎖住干涉儀的相位，此外為了降低反向進入干涉儀的雷射光對量測訊號產生影響，我們將正反進干涉儀的光源做了空間上的錯位並將鎖干涉儀的反打光強度調至非常的低，然後使用運算放大器搭配鎖相放大器將反打光的訊號放大取出來。
實驗的部份主要分成三個階段，首先我們先用古典雷射的光源做了一次DPS-QKD的原理測試，接著做了雷射光源的衰減並藉由帕松分佈的測量推算出一次事件在30ns時的平均光子數約0.1顆，最後我們用此衰減雷射光測試了DPS-QKD的原理，並推算出密鑰的產生率約為40kHz，量子位元錯誤率7.99%。

We use weak 1550nm laser with linewidth 2MHz as our source and construct an asymmetric Mach-Zehnder interferometer to perform differential phase shift quantum key distribution (DPS-QKD). To stabilize the interferometer, we use two mirrors in the long arm to fold the optical path in our Mach-Zehnder interferometer. Moreover, we test the interferometer’s visibility and stability.
In our experiment, we use attenuated laser to implement DPS-QKD. The laser source is attenuated to about 0.1 photon on average in 30 ns. Finally, we use the attenuated laser to test DPS-QKD, and find the generation key rate to be 40kHz, and QBER 7.99%.

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