Connecting Quantum Cities: Simulation of a Satellite-Based Quantum Network

TL;DR

This work tackles the challenge of linking metropolitan quantum networks into a continental-scale Quantum Internet using satellite-based channels. It introduces the Qloud architecture, where end users (Qlients) connect to a central Qonnector within a Quantum City, and satellites act as bacQbone nodes to interconnect distant Quantum Cities; the network is simulated with NetSquid, incorporating per-photon atmospheric transmission and orbit dynamics. Key findings show that nontrivial QKD rates are feasible with current or near-term technology, with performance highly sensitive to beam divergence and atmospheric conditions, and that alternative approaches such as high-altitude balloons or constellation deployments can complement satellite links. The study provides a modular simulation framework and architectural guidance to inform future mission design and the development of practical quantum networking capabilities for a scalable quantum Internet.

Abstract

We present and analyse an architecture for a European-scale quantum network using satellite links to connect Quantum Cities, which are metropolitan quantum networks with minimal hardware requirements for the end users. Using NetSquid, a quantum network simulation tool based on discrete events, we assess and benchmark the performance of such a network linking distant locations in Europe in terms of quantum key distribution rates, considering realistic parameters for currently available or near-term technology. Our results highlight the key parameters and the limits of current satellite quantum communication links and can be used to assist the design of future missions. We also discuss the possibility of using high-altitude balloons as an alternative to satellites.

Figures (13)

• Figure 1: Schematic of a Qloud: Quantum Cities connected through a backbone network of satellites (bacQbone nodes). A Quantum City is formed by a powerful central node (Qonnector) used as a server allowing end users (Qlients) to enjoy quantum-enhanced functionalities. The end users can also be powerful quantum machines (Qomputer nodes).
• Figure 2: The Quantum City topology. It is a star-type photonic quantum network with a special node in the middle, the Qonnector, that has high quantum capabilities. Each end node (Qlient, such as Alice or Bob) has limited quantum hardware and is connected to the Qonnector through an optical fiber.
• Figure 3: A satellite connecting Paris and Dutch Quantum Cities with downlinks only. Quantum City of Paris: Five Qlients are connected through optical fibers to a Qonnector located in the SU campus. The length of the fiber links are 1 m for the link Alice-Qonnector, 3 km for the link Bob-Qonnector, 7 km for the link Charlie-Qonnector, 19 km for the link Dina-Qonnector and 31 km for the link Erika-Qonnector. Dutch Quantum City: Three Qlients connected through optical fibers to a Qonnector placed in Delft. The length of the fiber are 54 km for the link Fatou-Qonnector, 9 km for the link Geralt-Qonnector and 13 km for the link Hadi-Qonnector.
• Figure 4: Elevation and distance to Paris and Delft of the (a) Micius, (b) Starlink, (c) Iridium and (d) Cosmo satellites in the time frame considered.
• Figure 5: Comparison of the average number of photons received at the Paris Qonnector for the four satellites considered for approximately 6000 photons sent by the satellite at each point of its orbit. For this simulation we suppose there are no aerosols in the atmosphere and we set the aperture radius of the receiving telescope at 1 m, the beam waist divergence at $5$$\mu$rad and the pointing error at $0.5$$\mu$rad.