Advances in Space Quantum Communications

TL;DR

This paper reviews recent advances and future prospects of space-based quantum communication technologies, emphasizing small satellite missions, key challenges, and the potential for a global quantum internet.

Contribution

It provides a comprehensive overview of current space quantum communication efforts, including recent demonstrations, challenges, and a roadmap for future development of a global quantum network.

Findings

Quantum networks are already implemented in several metropolitan areas.

Recent space-based quantum cryptography demonstrations show promising progress.

Small satellites are increasingly important for cost-effective global coverage.

Abstract

Concerted efforts are underway to establish an infrastructure for a global quantum internet to realise a spectrum of quantum technologies. This will enable more precise sensors, secure communications, and faster data processing. Quantum communications are a front-runner with quantum networks already implemented in several metropolitan areas. A number of recent proposals have modelled the use of space segments to overcome range limitations of purely terrestrial networks. Rapid progress in the design of quantum devices have enabled their deployment in space for in-orbit demonstrations. We review developments in this emerging area of space-based quantum technologies and provide a roadmap of key milestones towards a complete, global quantum networked landscape. Small satellites hold increasing promise to provide a cost effective coverage required to realised the quantum internet. We review the state of art in small satellite missions and collate the most current in-field demonstrations of quantum cryptography. We summarise important challenges in space quantum technologies that must be overcome and recent efforts to mitigate their effects. A perspective on future developments that would improve the performance of space quantum communications is included. We conclude with a discussion on fundamental physics experiments that could take advantage of a global, space-based quantum network.