The effect of atmospheric turbulent environment on the performance of free-space quantum communication is analysed. Based on the existing mathematical model of atmospheric turbulent fluid motion, the three most influential physical factors, i.e. wind speed, temperature and humidity, are abstracted out and simulated to study the variation of quantum channel utilisation, quantum channel entanglement, channel capacity and fidelity in amplitude damped channels under the atmospheric turbulent environment parameters. After a comprehensive analysis of the simulation results, it can be preliminarily judged that an increase in all three physical factors will increase the intensity of atmospheric turbulence and reduce the performance of quantum communication, and the magnitude of the influence is: temperature > wind speed > humidity. Therefore, corresponding adjustment strategies should be adopted to improve the communication performance of quantum communication and ensure the reliability of communication.
The effect of atmospheric turbulent environment on the performance of free-space quantum communication is analysed. Based on the existing mathematical model of atmospheric turbulent fluid motion, the three most influential physical factors, i.e. wind speed, temperature and humidity, are abstracted out and simulated to study the variation of quantum channel utilisation, quantum channel entanglement, channel capacity and fidelity in amplitude damped channels under the atmospheric turbulent environment parameters. After a comprehensive analysis of the simulation results, it can be preliminarily judged that an increase in all three physical factors will increase the intensity of atmospheric turbulence and reduce the performance of quantum communication, and the magnitude of the influence is: temperature > wind speed > humidity. Therefore, corresponding adjustment strategies should be adopted to improve the communication performance of quantum communication and ensure the reliability of communication.
Quantum communication is a frontier hotspot of current research, and it has ideal information security. In order to enable quantum systems in arid and desertified areas to work almost under all-weather condition, it is necessary to study the attenuation of free-space quantum signal transmission and the influence of the turbulence atmosphere carrying sand and dust on communication performance. Using Mie scattering theory, multiple scattering simulation method, and atmospheric turbulence theory, the attenuation of optical wave transmission in sand and dust turbulent atmospheric channels with different visibility, and the influence of multiple scattering and turbulence on attenuation are studied. The results show that the effect of multiple scattering increases with the decrease of visibility, the turbulence effect gradually strengthens with the increase of distance. According to the quantum amplitude damped channel model, the effects of multiple scattering and turbulence in the sand and dust turbulent atmosphere with different visibility on the quantum channel capacity, fidelity and bit error rate are analyzed. The results show that as the visibility decreases, the multiple scattering effect increases, resulting in the decrease of attenuation and bit error rate, but an increase in channel capacity, fidelity and the boundaries of security key rate. The existence of turbulence in the dust atmosphere will increase the attenuation and bit error rate, but reduce the channel capacity, fidelity and security key rate. It can be seen that the influence of multiple scattering and turbulence on the communication performance, when the visibility of the sand and dust atmosphere are both low, cannot be ignored. In practical applications, the relevant parameters of quantum communication should be adaptively adjusted according to the visibility and turbulence intensity to improve the probability, efficiency and reliability of quantum communication.
In recent years, the PM2.5 air pollution has been increasingly serious, which not only affects the air quality and visibility, but also has effects on free space optical signal transmission. However, the research about the relationship between the PM2.5 air pollution and the free space quantum communication has not yet been started. To investigate this relationship, the PM2.5 distribution function and its chemical extinction should be analyzed first. According to the degree of PM2.5 atmospheric pollution and the humidity of the atmosphere, the relationships among the PM2.5 index, the humidity of the atmosphere and the channel attenuation of the free space quantum communication can then be established. According to the amplitude damping channel and the depolarizing channel, the effects of the degree of PM2.5 air pollution on channel capacity, channel average fidelity, channel bit error rate are put out and simulated finally. Simulation results show that, if the air humidity is 30% and the PM2.5 index is 50, the channel capacity, channel average fidelity and the channel bit error rate of free space quantum communication will be 0.83, 0.91 and 0.0048 respectively. While the air humidity is 30% and the PM2.5 index is 300, the above channel parameters will be respectively 0.21, 0.56 and 0.0192. Further more, the channel average fidelity has an obvious difference between the two kinds of channel, and it is also related to the probability of the value of the source characters. Thus, the degree of PM2.5 air pollution has a significant effect on the performance of free space quantum communication. And, in order to improve the reliability of quantum communication in free space, the parameters should be adjusted adaptively based on the status of PM2.5 air pollution.
When the optical signal is transmitted in the free space, it inevitably passes through the atmosphere. The atmospheric aerosol is one of the most important components of the atmosphere, which not only affects the regional climate, but also influences the transmission of the free space optical signal. However, the study on the relationship between the non-spherical aerosols and the parameters of the free space quantum communication channel has not been carried out so far. To investigate this relationship, the spectral distribution function of the aerosol and its extinction factor should be analyzed first. According to three nonspherical aerosol particles: cylindrical particles, ellipsoidal particles and Chebyshev particles, the equation between channel attenuation of the free space quantum communication and the degree of quantum entanglement can then be established. After that, the effects of the relative humidity of the atmosphere on the degree of quantum entanglement and the fidelity of quantum communication can be analyzed and simulated finally. The simulation results show that the channel attenuations of the free space quantum communication are sequenced in ascending order as cylindrical particles, ellipsoidal particles, and Chebyshev particles, and their influences on the degree of quantum entanglement have different changing trends. When the transmission time is fixed, with the increase of aspect ratio of ellipsoidal particles, the degree of quantum entanglement shows a growing trend, with the increase of aspect ratio of cylindrical particles, the degree of quantum entanglement shows descending trend. With the increase of Chebyshev particle equivalent radius, the degree of quantum entanglement also shows the descending trend. When the relative humidity of the atmosphere is 0.2(0.9), the degree of quantum entanglement and the fidelity of quantum communication will be 0.72(0.75) and 0.32(0.22), respectively. It can be seen that the nonspherical aerosol particles and the relative humidity of the atmosphere each have a significant effect on the function of the free space quantum communication system. Therefore, in a practical free space quantum communication system, the shape factor of nonspherical aerosol particle, orientating factor, equivalent radius and the relative humidity of the atmosphere cannot be ignored, in order to improve the effectiveness and reliability of the free space quantum communication, the different parameters of the communication system should be adjusted adaptively.
In quantum satellite communication, when the optical quantum signal is transmitted between satellite and ground links, it will be affected by various natural environments.At the same time, haze has become one of the largest environmental problems in the world.Therefore, it is of great significance to study the communication performance of quantum satellites in haze atmosphere.In this paper, according to the scale distribution and vertical spatial concentration change of large aerosol haze particles, the extinction characteristic model of large aerosol haze particles and the attenuation model of atmospheric haze particle concentration and transmission height on quantum satellite ground link are established.Some important performance parameters in quantum satellite communication are analyzed for amplitude damping channel, depolarization channel and phase damping channel respectively, It includes the quantitative relationship between channel capacity, quantum fidelity, quantum bit error rate and entanglement and large aerosol haze particle concentration and transmission height.The simulation results show that with the increase of transmission distance and haze particle concentration, the channel capacity, quantum fidelity and entanglement of quantum satellite communication in different channels will decrease, and the bit error rate will increase.Therefore, the impact of large haze environment on quantum satellite communication should be fully considered in the actual process of quantum satellite communication, Adaptive adjustment of relevant parameters to ensure the normal operation of quantum satellite communication.
In order to study the influence of atmospheric turbulence on the polarization state of the free space quantum communication, the relationship between the refractive index and altitude, the refractive index structure constant and the turbulence dimension is deduced based on two different atmospheric refractive index structural constants models. The turbulence intensity factor κ is introduced and the equation of the variation of the quantum polarization degree with turbulence intensity is established. Through the simulation of the turbulent refractive index and the performance of four different polarization states in the low altitude turbulence environment, the results show that the atmospheric turbulence in the near ground will affect the fluctuation of the degree of polarization, and the degree of polarization varies linearly with the change of turbulence intensity. In the case of polarization |H>, the range of polarization |H> varies from 0 to 0.14 with the change of turbulence intensity. The influence of atmospheric turbulence on four different polarization states is different, and the degree of |H> and |V> depolarization is greater in the daytime and back. The depolarization degree of |-> at night is greater. The relationship between the degree of polarization and the change of turbulence intensity is analyzed by mathematical modeling, which is helpful to select the reasonable experimental scheme and compensate the change of polarization state in the aviation quantum Secure communication channel.
The key generation rates of free space quantum communication systems are vulnerable to the impact of variety natural conditions,so the character of random atmospheric turbulence is to be the primary factor taken into account to design free space quantum communication systems.A quantum key generation rate formula under the influence of turbulent flow was established,and the different intensity of the atmospheric turbulence with actual parameters impacting on the quantum key generation rate was researched.The results show that quantum key generation rate is close to 0 under the influence of strong atmospheric turbulence.