Recent experimental breakthroughs in satellite quantum communications have opened up the possibility of creating a global Quantum Internet using satellite links.
This approach appears to be particularly viable in the near term, due to the lower attenuation of optical signals from satellite to ground, and due to the currently short coherence times of quantum memories. The latter prevents ground-based entanglement distribution using atmospheric or optical-fiber links at high rates over long distances.
A team of researchers has proposed a global-scale Quantum Internet consisting of a constellation of orbiting satellites that provides a continuous, on-demand entanglement distribution service to ground stations. The satellites can also function as untrusted nodes for the purpose of long-distance quantum-key distribution.
They have developed a technique for determining optimal satellite configurations with continuous coverage that balances both the total number of satellites and entanglement-distribution rates.
Using this technique, they determined various optimal satellite configurations for a polar-orbit constellation, and analyzed the resulting satellite-to-ground loss and achievable entanglement-distribution rates for multiple ground station configurations.
They have also provided a comparison between these entanglement-distribution rates and the rates of ground-based quantum repeater schemes.
This work provides the theoretical tools and the experimental guidance needed to make a satellite-based global Quantum Internet a reality.
The paper has been published in npj Quantum Information.