Satellite-Based Continuous-Variable Quantum Communications: State-of-the-Art and a Predictive Outlook

The recent launch of the Micius quantum-enabled satellite heralds a major step forward for long-range quantum communication. Using single-photon discrete-variable quantum states, this exciting new development proves beyond any doubt that all of the quantum protocols previously deployed over limited ranges in terrestrial experiments can in fact be translated to global distances via the use of low-orbit satellites. In this work we survey the imminent extension of space-based quantum communication to the continuous-variable regime the quantum regime perhaps most closely related to classical wireless communications. The CV regime offers the potential for increased communication performance, and represents the next major step forward for quantum communications and the development of the global quantum internet. I. MOTIVATION AND INTRODUCTION Moore’s Law has remained valid for half-a-century! As a result, contemporary semi-conductor technology is approaching nano-scale integration. Hence nano-technology is about to enter the realms of quantum physics, where many of the physical phenomena are rather different from those of classical physics. Hence this treatise contributes towards completing the ‘quantum jig-saw puzzle’ by paving the way from classical wireless systems to their perfectly secure quantumcommunications counterparts, as heralded in [1], [2]. • The Inspiration: In order to circumvent the specific limitations of the classical wireless systems detailed in [1], we set out to bridge the separate classical and quantum worlds into a joint universe, with the objective of contributing to perfectly secure quantum-aided communications for anyone, anywhere, anytime across the globe, as indicated by the stylized vision of the nearfuture quantum communications scenario seen in Fig. 1. • The Reality: However, quantum processing is far from being flawless it has substantial challenges, as detailed in this contribution. Nonetheless, at the time of writing long-range quantum communications via satellites has