宇宙微波背景辐射对量子卫星信道性能及纠缠储备量的影响

2016年8月16日1时40分,我国长征二号运载火箭成功将世界首颗量子科学实验卫星"墨子号"发射升空。然而,有关宇宙微波背景辐射(Cosmic Microwave Background radiation,简称CMB)对量子卫星信道通信性能及纠缠储备量影响的研究,至今尚未展开。为此,本文根据CMB辐射谱与黑体辐射谱完美的拟合特性和小尺度范围内的各向异性,得到CMB绝对温度、辐射波长和黑体辐出度的关系。针对幅值阻尼信道,建立了CMB绝对温度、黑体辐出度、辐射波长、信道平均保真度和纠缠度之间的定量关系。仿真结果表明,当CMB绝对温度为2.7K和3.0K时,黑体辐出度分别为0.03 W·μm和3.72 W·μm,量子卫星信道的平均保真度和纠缠度分别为0.64、0.43和0.41、0.12。由此可见,CMB对量子卫星信道通信性能的影响极大。因此,在实际的量子卫星通信系统中,应根据不同的CMB绝对温度,自适应调节算符纠缠的幺正操作,改变信道的纠缠储备量,使信道纠缠度维持在相对稳定的状态,降低CMB对卫星信道通信性能的影响。

Influences of Cosmic Microwave Background Radiation on the Quantum Satellite Down-chain Communication Performance and Entanglement Reserves

At 1:40,On August 16th,2016,the Long March 2F carrier rocket in China was launching the Mo-tes successfully which is the world's first quantum science experiment satellite.Yet,the studies of the influence of Cosmic Microwave Background radiation(which refers to as the CMB) on quantum satellite down-chain communication performance and entanglement reserves has not launched up till now.According to the perfect fitting characteristics and the anisotropic in small scale range between CMB radiation spectrum and Blackbody radiation spectrum,the relationship among the CMB absolute temperature,the radiation wavelengths and the Blackbody radiant exitance can be proved.In view of the amplitude damping channel,the quantitative relationship among the CMB absolute temperature,the radiation wavelengths,the Blackbody radiant exitance,the channel average fidelity and quantum entanglement can be established.With the increase of CMB absolute temperature,the degree of quantum entanglement shows a descending trend.The simulation results show that when the CMB absolute temperature is 2.7 K and 3.0 K,the Blackbody radiant exitance is 0.03 W · μm ad 3.72 W · μm,and the channel average fidelity and quantum entanglement is 0.64 and 0.43,0.41 and 0.12.It can be seen that CMB has a significant effect on the function of the quantum satellite down-chain communication system.Therefore,in practical quantum satellite down-chain communication system,the operator entangled unitary operation should be adjusted to the difference of CMB absolute temperature,which can achieve the purpose of changing entanglement reserves and reduce the CMB effect on the quantum satellite down-chain communication system.