Experimental Shot Noise Measurement Using the Imperfect Detection - A Special Case for Pulsed Laser

Measuring the quantum fluctuations of a laser source is the first task in performing continuous variable quantum key distribution protocols. The quantum fluctuations of the source are measured using balanced homodyne detection. In this paper, we have measured the shot noise of a pulsed laser using imperfect homodyne detection. The imperfections accounted for in the detection process are a delay between the homodyne output arms and also due to the selection of the pulse integration window larger as well as smaller than the photo-current pulse width during the analysis. We have analyzed the imperfect detection results for two different experimental layouts, and a comparative study has been performed. From our analysis, it is evident that these imperfections play a significant role in balanced homodyne detection and must be optimized properly. Our results indicate that balanced homodyne detection can be performed using limited resources, which paves the way for easy experimental realization of optical homodyne tomography and continuous variable quantum key distribution in a laboratory setting.