Superactivation of the Asymptotic Zero-Error Classical Capacity of a Quantum Channel

TL;DR

This paper demonstrates that two quantum channels, each with zero zero-error capacity individually, can be combined to achieve perfect classical communication, revealing a superactivation phenomenon in quantum information theory.

Contribution

It proves for the first time that the zero-error classical capacity of quantum channels can be superactivated, showing a novel quantum effect not seen in classical channels.

Findings

Superactivation of zero-error classical capacity demonstrated

Two channels with zero capacity can enable perfect communication when combined

First example of superactivation in classical capacity of quantum channels

Abstract

The zero-error classical capacity of a quantum channel is the asymptotic rate at which it can be used to send classical bits perfectly, so that they can be decoded with zero probability of error. We show that there exist pairs of quantum channels, neither of which individually have any zero-error capacity whatsoever (even if arbitrarily many uses of the channels are available), but such that access to even a single copy of both channels allows classical information to be sent perfectly reliably. In other words, we prove that the zero-error classical capacity can be superactivated. This result is the first example of superactivation of a classical capacity of a quantum channel.