In this paper, a vector Monte Carlo (MC) method is proposed to study the influence of atmospheric scattering on polarization qubits for satellite-based quantum communication. The vector MC method utilizes a transmittance method to solve the photon free path for an inhomogeneous atmosphere and random number sampling to determine whether the type of scattering is aerosol scattering or molecule scattering. Simulations are performed for downlink and uplink. The degrees and the rotations of polarization are qualitatively and quantitatively obtained, which agree well with the measured results in the previous experiments. The results show that polarization qubits are well preserved in the downlink and uplink, while the number of received single photons is less than half of the total transmitted single photons for both links. Moreover, our vector MC method can be applied for the scattering of polarized light in other inhomogeneous random media.
In this paper, a vector Monte Carlo (MC) method is proposed to study the influence of atmospheric scattering on polarization qubits for satellite-based quantum communication. The vector MC method utilizes a transmittance method to solve the photon free path for an inhomogeneous atmosphere and random number sampling to determine whether the type of scattering is aerosol scattering or molecule scattering. Simulations are performed for downlink and uplink. The degrees and the rotations of polarization are qualitatively and quantitatively obtained, which agree well with the measured results in the previous experiments. The results show that polarization qubits are well preserved in the downlink and uplink, while the number of received single photons is less than half of the total transmitted single photons for both links. Moreover, our vector MC method can be applied for the scattering of polarized light in other inhomogeneous random media.
In this paper, we have mainly investigated the reconstruction of the polarization states of the incident light which passed through the turbid atmospheric media. Here, a novel polarization retrieve (PR) method is established using a Monte Carlo simulation algorithm, which is proposed to study the influence of particle scattering. The polarization states of the initial field could be retrieved accurately according to the polarization states of the scattered field and the Mueller matrix. In the case of a single homogeneous medium, the mean error of retrieved polarization is close to zero. We have also applied this method to complex atmospheric environments such as random-sized distribution particles and various index of refraction media. By comparison with the existing polarization maintaining method, the results indicate that the PR method is more applicable to disordered media with relatively larger particles. Moreover, the errors of the retrieved degree of polarization are below 0.11%, and the errors of the retrieved angle of polarization are below 0.54% in our mixed media model. So, this work will be very significant for polarizing quantum secure communication in scattering medium over a long-distance scope.
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.
Atmospheric turbulence and channel loss represent the primary limiting factors in ground-to-satellite quantum communication systems, yet their joint impact remains insufficiently characterized across diverse operational conditions. In this work, we develop a comprehensive and open atmospheric channel model for quantum optical links along ground-to-satellite paths, integrating altitude-dependent molecular and aerosol absorptions. The model is validated with available data from missions such as Micius and Hispasat, including a secondary viability assessment for a hypothetical Starlink-based quantum communication network, where we evaluate the predicted channel behavior in terms of single-photon transmittance and power balance, alongside the channel capacity of the link for uplink and downlink exclusively. Our comparative analysis demonstrates the ability of our channel model to predict real data under simple atmospheric behavior assumptions, which offer practical guidelines for the design and optimization of future quantum satellite missions.
The paper presents a simulator of a controlled atmospheric channel that we developed to search for ways to increase the performance and flexibility of quantum key distribution systems in free space, allowing us to simulate various interfering factors (scattering aerosol, temperature and temporary inhomogeneity of the environment) on one trace. Preliminary testing of the performance parameters of the experimental atmospheric communication channel, such as transmission speed, frame rate, total number of frames in the presence and absence of thermal disturbances, was carried out; the loss of laser radiation power and the stability of its polarization parameters for generating a quantum key encoded in the polarization states of photons were assessed.
Quantum entanglement is critical to build the backbone of all quantum technologies. Quantum networks, quantum computations, and quantum communication networking is based on long-range distribution of entangled photons and teleportation of photon qubit states. In order to understand quantum entanglement, characterization of atmospheric turbulence and its effects on propagating quantum states in free-space is essential. One method of photon entanglement is using a photon’s polarization. In this paper, we report results using polarization entangled signal and idler photons. The results may be applicable to support various quantum computing, encryption, and other qubit based high-performance communication protocols. Classically, the degradation of beam quality occurs due to many factors but primarily due to the distortion of spatial and temporal fields of refractive index. However, behavior of single photons through similar turbulent media creates a different set of challenges pointing to integrity of quantum states during propagation. We study this behavior by analyzing quantum states and the degree of entanglement in real-time and correlating it to known atmospheric models, (refractive index structure parameter), and relevant propagation path parameters. This experimental study was performed initially in a controlled laboratory environment, and then devised to be implemented outdoors over a 100-meter free space communication link.
Addressing the key technical challenges in air-sea cross-medium quantum communication between aircraft and submarines, this paper focuses on quantifying the link attenuation disparity between the uplink (submarine-to-aircraft) and downlink (aircraft-to-submarine) paths and optimizing system parameters. Using the Monte Carlo (MC) simulation method, a multi-medium transmission model encompassing the atmosphere, the air-sea interface, and seawater was constructed to precisely characterize the absorption and scattering behavior of optical signals in the complex cross-medium environment. Building on these attenuation characteristics, a secret key rate calculation model was derived in conjunction with the Gaussian-modulated coherent state (GMCS) Continuous-Variable Quantum Key Distribution (CV-QKD) protocol. The simulation results analyze the influence pattern of depth on the uplink and downlink key rates and clarify the underlying mechanisms for the attenuation disparity between the two paths. The study verifies that the downlink path possesses superior key rate performance due to weaker scattering and angular divergence effects. Furthermore, the paper investigates the modulating effect of modulation variance on the key rate and determines its optimal range.