采用矩阵形式描述光子的偏振态和大气散射理论, 分析了“BB84协议”中四个不同偏振光子经单次散射后光子的偏振度与前向散射角的关系。发现单次散射不改变偏振光子的总偏振度, 但改变偏振光子的线偏振度与圆偏振度, 尤其对垂直偏振光子的线偏振度与圆偏振度改变明显; 当前向散射角小于0.25 rad时, 四个不同偏振光子的线偏振度基本保持不变, 量子信息仍然保持; 同时分析了大气散射对不同波长的垂直偏振光子线偏振度的影响, 发现长波光子偏振度保持度高。

By using matrix to describe the polarization characteristic of photon and atmosphere scattering theory, the relationship between the polarization degree of four different polarized photons in “BB84 protocol” after single scattering and the forward scattering angle is analyzed. It is shown that single scattering does not have influence on photon polarization state, while the degree of linear and circular polarization are changed, especially, those of the perpendicular polarized photon are changed obviously. Also, it is founded that linear polarization degree of four different polarized photons keep unchanged when scattering angle is less than 0.25 rad, and the quantum information is still survive at the same time, we study the influence of atmosphere scattering on different wavelength polarized photons, it is shown that the polarization degree of longer wavelength photon change less than that of short wavelength photon.