Spooky action at a global distance: analysis of space-based entanglement distribution for the quantum internet

Abstract

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. In this work, we propose 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. We develop 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, we determine various optimal satellite configurations for a polar-orbit constellation, and we analyze the resulting satellite-to-ground loss and achievable entanglement-distribution rates for multiple ground station configurations. We also provide a comparison between these entanglement-distribution rates and the rates of ground-based quantum repeater schemes. Overall, our work provides the theoretical tools and the experimental guidance needed to make a satellite-based global quantum internet a reality.

Key Device and Materials Specifications for a Repeater Enabled Quantum Internet

“…The reported value of 1.1 Hz would be achievable (when averaged over a day) with more such satellites giving continuous coverage. These estimates are comparable to that presented in a recent work on satellite networks [65]. This implies that the GBL to SBL threshold will be between 500-1500 km based on the number of satellites (figure 4).…”

Policies for elementary links in a quantum network

“…Furthermore, because our results apply to elementary links consisting of an arbitrary number of nodes and to any noise model for the quantum memories, they can be applied to protocols that go beyond bipartite entanglement distribution, namely to protocols for distributing multipartite entanglement. We also expect our results to be useful in the analysis of entanglement distribution using all-photonic quantum repeaters [69], and in the analysis of entanglement distribution using satellite-based quantum networks [70][71][72][73][74], in which an elementary link can easily be on the order of 1000 km [38] while still having a high fidelity. Initial applications of the results of this work to satellite-based elementary links can be found in [75,Chapter 7].…”

Proposal for space-borne quantum memories for global quantum networking

“…Atmosphere constituents cause absorption and scattering of the optical signal, those effects depend on the signal wavelength. The atmospheric loss that includes absorption as a function of elevation angle of θ is given by 28 :…”

“…In satellite QKD (SatQKD) [22][23][24][25] , the transmission loss through the vacuum of space is dominated by diffraction that has an inverse square scaling instead of exponential. However, the connection distance for SatQKD is primarily limited by the line-of-sight between satellite and ground station, which in turn depends on its orbit unless the satellite acts as a trusted node [26][27][28][29][30] . To establish a global quantum network without trusted nodes will require overcoming the above limitations.…”