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.
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 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.
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.
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.
Abstract Soot aerosol is an important part of atmospheric aerosol, which has important influence on the propagation of quantum signal. In order to study the influence of soot aerosol on satellite-ground quantum communication, according to the size distribution parameter and extinction coefficient of the soot aerosol, the influence of the concentration of the soot aerosol particles and the transmission distance on the attenuation of the link is analyzed. The simulation experiments of channel capacity, channel fidelity and channel bit error rate (Ber) are carried out with amplitude-damped channel. The simulation results show that the soot aerosol concentration increases from 2.1×10 6 / m 3 to 3.2 10× 6 / m 3 , the link attenuation factor increases from 0.3dB/ km to 0.46dB/ km, the fidelity decreases from 0.98 to 0.97, and the bit error rate increases from 0.0087 to 0.0122 at a transmission distance of 3km . hhen the transmission distance is 6km and the particle concentration is 2.1×10 6 / m 3 , 2.7 10× 6 / m 3 and 3.9×10 6 / m 3 , the channel capacity increases from 1.078 to 1.0809, and then decreases to 1.0804. Therefore, the soot aerosol has influence on the performance of satellite-ground quantum communication, and the degree of influence is different. In order to ensure the reliability of quantum communication between satellite and ground, the parameters can be adjusted to ensure the normal transmission of quantum signal.
Quantum communication provides high security and privacy, offering effective protection against eavesdropping and decryption during information transmission. Its inherent unconditional security addresses information security issues effectively. Dust particles, as prevalent environmental factors in the atmosphere, exert negative impacts on both traditional and quantum communication. Due to the higher requirements for signal fidelity and stability in quantum communication, the impact of dust particles may be more significant. To investigate the effect of dust aerosol particles on the performance of satellite-ground quantum communication links, we established quantitative relationships between particle number concentration and transmission distance, and the link attenuation, as well as the channel capacity, system survival function, and error rate of three noise channels: amplitude damping, bit-flip, and depolarizing channels. Using Matlab, we conducted experimental simulations based on the size distribution function of dust aerosol particles and Mie scattering theory. The simulation results indicate that when the transmission distance is 6 km and the particle concentration of dust aerosols increases from20/m3to55/m3, the channel attenuation factor increases from84.35dB/kmto232dB/km. The capacity of the amplitude damping channel decreases from0.6486bit/sto0.3943bit/s, and the survival function of the amplitude damping channel decreases to 0.9059. When the particle concentration is900/m3and the transmission distance increases from 3km to 8km, the bit error rate increases from 0.03 to 0.2. The results indicate that dust aerosols have impacted various aspects of satellite-to-ground communication, each in different ways, highlighting the importance of considering their influence. Therefore, when implementing quantum communication in practice, it is essential to adjust the parameters accordingly to ensure the normal operation of communication.
Quantum information technology is an emerging interdisciplinary field that utilizes the properties of quantum mechanics and combines classical information theory and methods to represent and process information. Among them, quantum secure communication (especially quantum key distribution technology) is considered one of the most likely directions to be put into practical use first. According to different propagation media, quantum key distribution can be divided into quantum key distribution in optical fibers and quantum key distribution in free space. There is nobirefringence effect in optical fibers of the free space, and there is no need to lay optical cables. Once the technology is mature, it can be used for secure ground satellite communication, building a global network of quantum communication networks, and has good development prospects. Due to the complex weather conditions above the channel, the attenuation of laser power in the atmosphere is difficult to predict. This article focuses on theoretical modeling of commonly used aerosols in channels. By analysing the advantages and disadvantages of existing models, a micro particle scattering method is proposed to construct atmospheric attenuation, which introduces geometric scattering and cladding particle scattering. Extended Mie scattering models are constructed separately, and the applicable objects and scope of the scattering models are explained. Mie scattering is a theoretical model for analyzing the attenuation of fog aerosols, while geometric scattering is a theoretical method for analyzing large-scale aerosols such as rainfall. For haze aerosols, a blanket particle scattering model is proposed for theoretical analysis. When the aerosol concentration is high, Monte Carlo method can be combined for optimization. Then, based on the layered theory, the attenuation of laser propagation along any path is derived. Finally, attenuation models for fog, rain, and haze were constructed. On this basis, the attenuation of laser propagation along any path is derived. Then, the simulation results are compared with mainstream commercial software, and the relative error of operation is less than 5%. Finally, the results were compared uniformly to determine the strength of aerosol attenuation on the 1.55u m laser. The simulation results of the model can serve as a theoretical basis for the adaptive power adjustment of the free space quantumkey distribution system at the transmitting, ensuring the system's error rate.