How Deep the Theory of Quantum Communications Goes: Superadditivity, Superactivation and Causal Activation
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In the theory of quantum communications, a deeper structure has been recently unveiled – mainly within the physics community – 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 paper 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, by adopting a communication engineering perspective.
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