An improved scheme that the random matrix transformation used for BB84 protocol

The bit error rate is raised by the presence of the noise when the quantum key transmits in practice. So both sides of communication can not judge the presence of eavesdropping. For this issue, an improved scheme based on BB84 protocol is proposed by a paper of Luanxin that a matrix transformation is carried out for every quantum of both sides. The advantage of the transformation is that the eavesdropper can be found easily. But the disadvantage is that it leads to a low key generation rate. In this paper, an improvement that a matrix transformation is carried out randomly for the quantum of both sides based on the scheme of Luanxin is proposed. The result shows that not only the presence of eavesdropping can be judged easily, but also the key generation rate is increased significantly.