The quantum based satellite communication offers a secure way for key distribution which is essential for symmetric keys based transmi ssion. For modeling this type of communication, we created a mathematical model which is based on the behavior of singlephoton sources and detectors and on the losses orig inated from beam spreading and pointing error. Based on this model, we developed a simulator software to study the quantum communication over space-space links, e.g., between two satellites. We analyzed the performance of three quantum key distribution protocols—BB84, B92, S09—on different space-space links. Two of the main parameters during the analysis were the size of the necessary aperture for a successful space-space communication and the length of the communication channel. Our results show that the three mentioned QKD protocols are feasible when using satellite-satellite links.
The quantum based satellite communication offers a secure way for key distribution which is essential for symmetric keys based transmi ssion. For modeling this type of communication, we created a mathematical model which is based on the behavior of singlephoton sources and detectors and on the losses orig inated from beam spreading and pointing error. Based on this model, we developed a simulator software to study the quantum communication over space-space links, e.g., between two satellites. We analyzed the performance of three quantum key distribution protocols—BB84, B92, S09—on different space-space links. Two of the main parameters during the analysis were the size of the necessary aperture for a successful space-space communication and the length of the communication channel. Our results show that the three mentioned QKD protocols are feasible when using satellite-satellite links.
Quantum communications offers secure and reliable key distribution protocols. The quantum solutions can be used in laser based satellite communications. However, many different physical parameters need to be taken into account to model a free-space optical channel. To complete the determination of e.g., the Quantum Bit Error Rate, a series of derived procedures are needed to execute, which has high complexity. An ideal solution is to place the calculations for simulation software, which issues all of the interpretable information about the properties of the communication channel. We created a free-space optical Earth-space channel model, developed a simulator and modeled the behavior of three quantum key distribution protocols for a given parameter set.
Quantum Key Distribution (QKD) has emerged as a fundamentally secure approach to communication in the era of quantum computing, offering protection against threats posed to classical cryptographic schemes such as RSA and Diffie-Hellman. This thesis presents a comprehensive performance analysis of satellite-based QKD protocols, focusing on both prepare-and-measure and entanglement-based schemes under realistic atmospheric and operational conditions. The study begins by introducing the theoretical foundations of quantum communication, including qubits, entanglement, and quantum entropy, and motivates the need for satellite-based QKD to overcome the distance limitations of fiber-based systems. Subsequently, the thesis evaluates four prominent QKD protocols-BB84, B92, BBM92, and E91-using a circular beam propagation model that incorporates atmospheric effects such as diffraction, turbulence, attenuation, and pointing errors, along with environmental noise contributions for uplink and downlink. Comparative numerical simulations reveal that protocol performance is strongly influenced by channel asymmetries, beam propagation characteristics, and noise, providing guidance on optimal protocol selection for low Earth orbit (LEO) satellite links. The research further investigates high-dimensional (HD) QKD protocols, specifically HD-BB84 and HD-Extended B92, using the elliptic-beam approximation to account for turbulence-induced distortions for both uplink and downlink. Simulations under vary ing system dimensions, weather conditions, and zenith angles demonstrate that HD-BB84 achieves higher key rates, superior noise tolerance, and more favorable probability distributions of the key rate compared to HD-Extended B92, highlighting the advantages of high-dimensional encoding for robust satellite-based QKD.
Abstract An ideal QKD implementation that provides the promising unconditional security using single photon laser source is not practically easy, also sending these photons over a fiber channel affects the maximum distance of link up to few hundreds of kilometers because of the receiver’s detectors losses. Therefore, the achievement of a global quantum network is not easy, and the need to use LEO satellites [1,2] for establishing quantum links makes the job easier as quantum free space link provides much less losses to the link than fiber links. Nowadays, a quantum communication link can be established by satellites through free space. in this paper, we propose an implementation [3] of a satellite-based quantum key distribution using decoy-state protocol [4], we then compare this protocol with the BB-84 protocol [3] against security and the key length of the generated shared key.
Satellite-based free-space quantum key distribution (QKD) provides a practical framework for achieving secure global communication beyond the limitations of optical fibers. In this work, the quantum bit error rate (QBER) and secure key rate of four representative protocols-BB84, B92, BBM92, and E91 are investigated over low earth orbit (LEO) links in both uplink and downlink configurations. The optical link is modeled using a Gaussian beam formalism, incorporating the effects of diffraction, pointing errors, atmospheric turbulence, and background noise contributions. The protocols are examined under day and night-time operating conditions, and their dependence on the zenith angle is analyzed. The findings show that downlink links generally exhibit lower QBER and higher secure key rates than uplinks, and among prepare-and-measure schemes, BB84 consistently outperforms B92, while in entanglement-based approaches, BBM92 achieves higher key rates than E91.
Abstract The establishment of a world-wide quantum communication network relies on the synergistic integration of satellite-based links and fiber-based networks. The first are helpful for long-distance communication, as the photon losses introduced by the optical fibers are too detrimental for lengths greater than about 200 km. This work aims at giving, on the one hand, a comprehensive and fundamental model for the losses suffered by the quantum signals during the propagation along an atmospheric free-space link. On the other hand, a performance analysis of different quantum key distribution (QKD) implementations is performed, including finite-key effects, focusing on different interesting practical scenarios. The specific approach that we chose allows to precisely model the contribution due to different weather conditions, paving the way towards more accurate feasibility studies of satellite-based QKD missions.