Research On Quantum Key Communication In Free Space

Discussions about quantum cryptography communication in free space are firstly put forward through advancing the topic of the importance of secret communication nowadays. Advantages of using quantum cryptography into the application of communication fields are also pointed out. Then its developing status, existing problems and developing future are analyzed one by one. Further more, the physical foundations and informational bases of free space quantum cryptography are introduced. Finally, the emphases are focused on the present quantum cryptography experiments and an improved scheme toward one of them are shown in the paper, which mainly includes rectifications of two parts of the original idea: the atomic vapor filter the paper advances could better reduce the interference of background light which help increase the signal to noise ratio; the multi-input-multi-output system mentioned in the paper in its communication channel could effectively increase the communication capacity of it, which also contributes to the improvement of its signal to noise ratio.