We give a feasibility analysis on entanglement distribution in quantum repeater-based space quantum communication. After a quick review of the Quantum Repeater techniques, two typical communication scenarios are provided as examples and a further feasibility analysis for entanglement distribution in general deep space quantum communication on link requirements, transmission attenuations and terminal requirements are documented.
We give a feasibility analysis on entanglement distribution in quantum repeater-based space quantum communication. After a quick review of the Quantum Repeater techniques, two typical communication scenarios are provided as examples and a further feasibility analysis for entanglement distribution in general deep space quantum communication on link requirements, transmission attenuations and terminal requirements are documented.
Entanglement distribution is a fundamental building block of quantum communication networks, enabling the secure and reliable exchange of quantum information over long distances. Unlike classical communication, quantum networks exploit the unique properties of quantum entanglement to support applications such as quantum key distribution, quantum teleportation, distributed quantum computing, and networked quantum sensing. Although significant progress has been made in recent years, the efficient generation, transmission, and preservation of entangled states remain major research challenges due to photon loss, decoherence, and limitations in current communication infrastructure.This review provides a comprehensive overview of entanglement distribution in quantum communication networks, focusing on the technologies that enable practical implementation and the latest experimental developments. It discusses key approaches for generating and distributing entangled photons through optical fibers, free-space links, and satellite-based communication, together with supporting technologies such as quantum repeaters, quantum memories, and photonic devices. The review also examines recent experimental demonstrations that have advanced long-distance quantum communication while highlighting the technical barriers that must be overcome for large-scale deployment. Finally, emerging applications and future research directions are presented, including the development of scalable quantum networks, the quantum internet, and secure global communication systems. This review aims to provide researchers and students with a clear understanding of the current state of entanglement distribution and its growing role in next-generation quantum communication technologies.
Satellite optical links may be able to extend quantum communication range beyond that which is possible through optical fibres which are constrained by exponential loss scaling. Quantum repeaters have been proposed to mitigate high channel losses in both fibre and satellite links. Although satellite quantum repeaters could improve entanglement distribution efficiency, the attempt rate is constrained by classical communication latency in the entanglement swapping step. Direct entanglement distribution does not suffer this latency and can therefore compensate for high dual-downlink losses by increasing the source rate. A systematic comparative analysis of repeater-assisted and direct entanglement distribution rates using a satellite is absent from the literature. In addition to entanglement distribution rates, a detailed analysis of the fidelity of entanglement distributed by repeater-assisted satellite links has yet to be performed. Here, we develop an in-depth framework for describing a space quantum link consisting of a single satellite and two ground stations. We compare the entanglement distribution rates of direct and repeater-assisted satellite entanglement distribution, taking into account variations in overpass geometry and quantum memory capacity. The long-term entanglement distribution performance to different pairs of major cities is also considered, and the altitudinal dependence is explored. Furthermore, we develop a Monte Carlo model of the repeater satellite to explore the effect that different memory management policies and capacities have on the waiting time statistics of memory qubits. From these statistics we calculate the fidelity distributions of the entangled pairs established between the ground stations. These results will inform mission design for future space-borne quantum repeater nodes, as well as requirements on space-based memory platforms.
A large scale quantum network requires the distribution of high-fidelity end-to-end entanglement. To overcome the range limitations inherent to terrestrial fiber, a leading architecture has emerged: satellite-based sources transmitting entanglement to quantum repeaters on the ground. By bridging the gap between abstract analytical frameworks and computationally heavy numerical simulations, this paper provides the first quantitative answer to the question of such a network's achievable performance with current and near-term space technology, while accounting for entanglement swapping and purification. This is achieved by integrating a detailed physical model of a satellite-to-ground link into an analytical entanglement resource estimation framework for quantum repeaters, enabling an optimization of the end-to-end entanglement rate. Our analysis, performed across leading quantum hardware platforms, shows that Low Earth Orbit satellite constellations combined with quantum repeaters employing Neutral Atom or Nitrogen and Silicon Vacancy qubits, could enable a global quantum network, distributing entanglement over distances up to 20,000 km, sufficient for connecting any two points on Earth. This work highlights the major bottlenecks in space and quantum hardware technologies, which need to be addressed, thereby guiding informed investments necessary for enabling a large scale quantum network.
We analyze how the performance of a quantum-repeater network depends on the protocol employed to distribute entanglement, and we find that the choice of repeater-to-repeater link protocol has a profound impact on entanglement-distribution rate as a function of hardware parameters. We develop numerical simulations of quantum networks using different protocols, where the repeater hardware is modeled in terms of key performance parameters, such as photon generation rate and collection efficiency. These parameters are motivated by recent experimental demonstrations in quantum dots, trapped ions, and nitrogen-vacancy centers in diamond. We find that a quantum-dot repeater with the newest protocol ('MidpointSource') delivers the highest entanglement-distribution rate for typical cases where there is low probability of establishing entanglement per transmission, and in some cases the rate is orders of magnitude higher than other schemes. Our simulation tools can be used to evaluate communication protocols as part of designing a large-scale quantum network.
Satellite constellations have the potential for enabling globe-spanning quantum networks for secure communication, entanglement distribution, and eventually the quantum internet. The architecture, design, and operation of such space quantum networks face several challenges, from scheduling, performance analysis and optimization, and overcoming issues such as weather effects. Here, we summarise recent research into constellation design, optimization, and the incorporation of quantum memories and repeaters in space quantum communication links. These preliminary works offer guidance for future development efforts for long-term space quantum communication systems.
The realization of the quantum internet as an interconnected network of quantum hardware requires the distribution of entanglement over long distances. Due to the exponential photon loss in optical fibers, the necessary communication rates for end-user applications cannot be achieved if direct links over several hundred kilometers are required. Two possible solutions to increase the link distance are the implementation of quantum repeaters and the use of free-space optical satellite links. A natural extension would be to combine both approaches, by using satellites as quantum repeater nodes and take advantage of the low losses in free-space. However, due to the higher technological requirements for space-based technologies and the already low communications losses in free-space, it is not yet clear whether satellite- based quantum repeaters can lead to an additional improvement in the communication rate. Here we show for which operating scenarios a satellite-based quantum repeater outperforms a single satellite for entanglement distribution. To this end, we developed a satellite simulation software that includes a model of the optical link model and of entanglement swapping in order to analyze entanglement distribution rates of the satellite-based quantum repeater and single satellite. The simulation captures important effects such as the single-mode fiber coupling efficiency, adaptive optics corrections, decoherence and decay of information in the quantum memory as well as its retrieval efficiency. Based on these effects, we show advantages and challenges of satellite constellations for quantum communications in low, medium and geosynchronous orbits.