How Deep the Theory of Quantum Communications Goes: Superadditivity, Superactivation and Causal Activation

TL;DR

This paper explores advanced quantum communication phenomena like superadditivity, superactivation, and causal activation, highlighting their implications for understanding the fundamental limits of quantum channels in communication engineering.

Contribution

It provides an accessible overview and guide to key quantum communication phenomena, emphasizing their significance for communication engineering and fundamental limits.

Findings

Quantum capacity exhibits superadditivity and superactivation.

These phenomena challenge classical notions of channel capacity.

The paper offers a comprehensive literature guide for engineers.

Abstract

In the theory of quantum communications, a deeper structure has been recently unveiled, showing that the capacity does not completely characterize the channel ability to transmit information due to phenomena -- namely, superadditivity, superactivation and causal activation -- with no counterpart in the classical world. Although how deep goes this structure is yet to be fully uncovered, it is crucial for the communication engineering community to own the implications of these phenomena for understanding and deriving the fundamental limits of communications. Hence, the aim of this treatise is to shed light on these phenomena by providing the reader with an easy access and guide towards the relevant literature and the prominent results from a communication engineering perspective.