Micius quantum experiments in space

TL;DR

This paper reviews the progress of space-based quantum experiments, especially focusing on the Micius satellite, demonstrating the potential for global quantum communication and fundamental physics tests over large distances.

Contribution

It provides a comprehensive overview of recent advancements in satellite-based quantum experiments, highlighting the Micius satellite's role in quantum communication and fundamental tests.

Findings

Successful demonstration of quantum key distribution via satellite

Potential for global-scale quantum networks using space-based technology

Reduced photon loss and decoherence in space experiments

Abstract

Quantum theory has been successfully validated in numerous laboratory experiments. But would such a theory, which excellently describes the behavior of microscopic physical systems, and its predicted phenomena such as quantum entanglement, be still applicable on very large length scales? From a practical perspective, how can quantum key distribution -- where the security of establishing secret keys between distant parties is ensured by the laws of quantum mechanics -- be made technologically useful on a global scale? Due to photon loss in optical fibers and terrestrial free space, the achievable distance using direct transmission of single photons has been limited to a few hundred kilometers. A promising route to testing quantum physics over long distances and in the relativistic regimes, and thus realizing flexible global-scale quantum networks is via the use of satellites and space-based technologies, where a significant advantage is that the photon loss and turbulence predominantly occurs in the lower ~ 10 km of the atmosphere, and most of the photons' transmission path in the space is virtually in vacuum with almost zero absorption and decoherence. In this Article, we review the progress in free-space quantum experiments, with a focus on the fast-developing Micius satellite-based quantum communications. The perspective of space-ground integrated quantum networks and fundamental quantum optics experiments in space conceivable with satellites are discussed.