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arXiv:2610.26034

A Dual-Uplink Dual-Satellite Architecture for Entanglement Distribution

Charilaos C. Angelidis, Ioannis K. Marmorkos

quant-phcs.NISubmitted Oct 19, 2026• Announced Oct 20, 2026• 0 citations
arXivHTMLPDF

Abstract

Satellite-based quantum links are a promising enabler of long-distance entanglement distribution, overcoming the exponential losses of optical fibers. In uplink architectures, entangled photons are generated at ground stations and transmitted to orbiting satellites, reducing space-segment complexity but introducing significant atmospheric and geometric losses. Single-satellite dual-uplink configurations are additionally limited by the requirement of simultaneous visibility between both ground stations and the satellite. In this work, we investigate a dual-uplink dual-satellite network architecture and compare its performance with the single-satellite scheme under identical physical assumptions. The proposed topology introduces an inter-satellite link (ISL) that decouples the ground-station separation from the atmospheric uplink geometry. A realistic channel model is employed, incorporating geometric attenuation, atmospheric turbulence, background noise, and Bell-state measurement efficiency. The overall success probability and practical fidelity are evaluated as functions of satellite altitude and ground-station separation. Our results show that while the single-satellite configuration is suitable for regional-scale networks, it becomes infeasible for large separations due to geometric constraints. The proposed dual-satellite architecture mitigates this limitation and significantly extends the achievable communication distance, representing a key step toward scalable quantum internet infrastructures.

Comments
19 pages, 9 figures, submitted to International Journal of Quantum Information

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Satellite-based quantum links are a promising enabler of long-distance entanglement distribution, overcoming the exponential losses of optical fibers. In uplink architectures, entangled photons are generated at ground stations and transmitted to orbiting satellites, reducing space-segment complexity but introducing significant atmospheric and geometric losses. Single-satellite dual-uplink configurations are additionally limited by the requirement of simultaneous visibility between both ground stations and the satellite.
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Our results show that while the single-satellite configuration is suitable for regional-scale networks, it becomes infeasible for large separations due to geometric constraints. The proposed dual-satellite architecture mitigates this limitation and significantly extends the achievable communication distance, representing a key step toward scalable quantum internet infrastructures.
Abstract Quantum repeaters and satellite-based optical links are complementary technological approaches to overcome the exponential photon loss in optical fibers and thus allow quantum communication on a global scale. We analyze architectures which combine these approaches and use satellites as quantum repeater nodes to distribute entanglement to distant optical ground stations. Here we simulate dynamic, three-dimensional ground station passes, going beyond previous studies that typically consider static satellite links. For this, we numerically solve the equations of motion of the dynamic system consisting of three satellites in low Earth orbit. The model of the optical link takes into account atmospheric attenuation, single-mode fiber coupling, beam wandering and broadening, as well as adaptive optics effects. We derive analytical expressions for the Bell state measurement and associated error rates for quantum memory assisted communications, including retrieval efficiency and state coherence. We consider downlink and uplink architectures for continental and intercontinental connections and evaluate the impact of satellite altitude and inter-satellite distance on the expected entanglement swapping rate. Our simulation model enables us to design different orbital configurations for the satellite constellation and analyze the annual performance of the quantum repeater under realistic conditions.
Quantum repeaters and satellite-based optical links are complementary technological approaches to overcome the exponential photon loss in optical fibers and thus allow quantum communication on a global scale. We analyze architectures which combine these approaches and use satellites as quantum repeater nodes to distribute entanglement to distant optical ground stations. Here we simulate dynamic, three-dimensional ground station passes, going beyond previous studies that typically consider static satellite links. For this, we numerically solve the equations of motion of the dynamic system consisting of three satellites in low Earth orbit. The model of the optical link takes into account atmospheric attenuation, single-mode fiber coupling, beam wandering and broadening, as well as adaptive optics effects. We derive analytical expressions for the Bell state measurement and associated error rates for quantum memory assisted communications, including retrieval efficiency and state coherence. Our simulation model enables us to design different orbital configurations for the satellite constellation and analyze the annual performance of the quantum repeater under realistic conditions.
Significant work has been done to develop quantum satellites, which generate entangled pairs in space and distribute them to ground stations separated some distance away. The reverse “uplink” case, where pairs are generated on the ground and swapped on the satellite using an optical Bell measurement, has not been seriously considered due to a prevailing assumption that it is practically infeasible. In this paper, we illustrate the feasibility of performing Discrete Variable photonic Bell measurements in space by conducting a detailed numerical analysis to estimate the channel efficiency and attainable pair fidelity for various satellite-station configurations. Our model accounts for a wide range of physical effects such as atmospheric effects, stray photons, and mode mismatch. Our findings show promise toward the feasibility of photonic Bell measurements in space, which motivates future research toward large-scale satellite-based uplink entanglement distribution.
Satellite quantum communications are emerging within the panorama of quantum technologies as a more effective strategy to distribute completely secure keys at very long distances, therefore playing an important role in the architecture of a large-scale quantum network.In this work, we apply and extend recent results in free-space quantum communications to determine the ultimate limits at which secret (and entanglement) bits can be distributed via satellites.Our study is comprehensive of the various practical scenarios, encompassing both downlink and uplink configurations, with satellites at different altitudes and zenith angles.It includes effects of diffraction, extinction, background noise, and fading, due to pointing errors and atmospheric turbulence (appropriately developed for slant distances).Besides identifying upper bounds, we also discuss lower bounds, i.e., achievable rates for key generation and entanglement distribution.In particular, we study the composable finite-size secret key rates that are achievable by protocols of continuous variable quantum key distribution, for both downlink and uplink, showing the feasibility of this approach for all configurations.Finally, we present a study with a sun-synchronous satellite, showing that its key distribution rate is able to outperform a ground chain of ideal quantum repeaters.
Finding a realistic and efficient scheme that allows for the distribution of entanglement at global scales constitutes a challenging task with a satisfactory solution yet to be found. Due to the exponential losses experienced in optical fibers and the absence of a direct line-of-sight between opposite sides of Earth, employing a quantum repeater chain will likely be inevitable to achieve this task. Long-distance terrestrial fiber connections would require a huge number of intermediate repeater nodes and is further hindered by inaccessible terrain, so that quantum repeaters realized via free-space optical links between satellites constitute a promising alternative. These, however, introduce their own set of challenges, such as the dynamic behaviour of the satellites in orbit and a high baseline of losses due to the satellite-to-ground connection. In this work, we discuss the general scaling properties of free-space optical quantum repeaters and combine them with the geometric constraints imposed by satellite connections to propose and assess a two-node two-satellite quantum repeater architecture that allows entanglement distribution at truly global scales whilst also being able to adaptively be used as a one-node one-satellite repeater to efficiently cover shorter distances. We provide an analysis of the connection time and the effective transmission and show that two MEO satellites are sufficient to distribute entanglement between ground stations with arbitrary distances inside the orbital plane. We deem our architecture as one of the most promising in terms of performance, connection distance and flexibility whilst using only two satellites, alleviating the extreme technical challenge of realizing a quantum repeater constellation.
Establishing information-theoretically secure communication between arbitrary locations on Earth is a central goal of quantum networking, for which space-based distribution of quantum entanglement is a leading approach. Modelling and analysis of the performance of satellite entanglement pair distribution is therefore important for the architecture and design of future constellations and space systems. However, entanglement-based quantum key distribution in the absence of quantum repeaters, is especially prone to finite-key effects due to low coincident count rates compared to trusted-node single-path links. Quantifying these effects under realistic orbital conditions is therefore essential for the design of practical satellite quantum communication systems. Here, we develop a high-fidelity model of pair distribution from a low-Earth-orbit satellite that captures orbital dynamics, elevation-dependent loss, background noise, and extraneous detector effects. Integrating this with a finite-key security framework for the BBM92 protocol, we optimise the secret key length across different overpass geometries, orbital altitudes, and optical ground station (OGS) separations. We show that secure key generation remains feasible in early clear daytime conditions using baseline parameters representative of current technologies, while showing that modest system improvements could further extend daytime operation. Finally, we evaluate the annual secret key performance for representative intercity-scale OGS pairings. Our results provide quantitative performance bounds and practical design guidelines for near-term entanglement-based satellite QKD, enabling informed trade-offs between satellite payload complexity, ground infrastructure, and achievable secure key throughput.