Physical Layer Aspects of Quantum Communications: A Survey

TL;DR

This survey reviews the physical layer aspects of quantum communication, highlighting unique challenges, techniques, and potential synergies with classical systems to guide future development of high-fidelity quantum networks.

Contribution

It provides a comprehensive overview of quantum physical layer components, techniques, and challenges, emphasizing commonalities and differences with classical communication systems.

Findings

Analysis of quantum channels and use cases over optical media

Survey of quantum sources, detectors, and modulation techniques

Discussion of spatial multiplexing and MIMO in quantum systems

Abstract

Quantum communication systems support unique applications in the form of distributed quantum computing, distributed quantum sensing, and several cryptographic protocols. The main enabler in these communication systems is an efficient infrastructure that is capable to transport unknown quantum states with high rate and fidelity. This feat requires a new approach to communication system design which efficiently exploits the available physical layer resources, while respecting the limitations and principles of quantum information. Despite the fundamental differences between the classic and quantum worlds, there exist universal communication concepts that may proven beneficial in quantum communication systems as well. In this survey, the distinctive aspects of physical layer quantum communications are highlighted in a attempt to draw commonalities and divergences between classic and quantum communications. More specifically, we begin by overviewing the quantum channels and use cases over diverse optical propagation media, shedding light on the concepts of crosstalk and interference. Subsequently, we survey quantum sources, detectors, channels and modulation techniques. More importantly, we discuss and analyze spatial multiplexing techniques, such as coherent control, multiplexing, diversity and MIMO. Finally, we identify synergies between the two communication technologies and grand open challenges that can be pivotal in the development of next-generation quantum communication systems.