Zero-error classical capacity of qubit channels cannot be superactivated

TL;DR

This paper proves that qubit channels cannot exhibit superactivation of zero-error classical capacity, unlike some higher-dimensional quantum channels, highlighting a fundamental limitation in quantum information transmission.

Contribution

It establishes that superactivation of zero-error classical capacity is impossible for qubit channels, providing a key limitation in quantum communication theory.

Findings

Qubit channels cannot be superactivated

Superactivation is unique to higher-dimensional channels

Limits on zero-error classical capacity in qubit systems

Abstract

It was shown [T.S. Cubitt et al., IEEE Trans. Inform. Theory 57, 8114 (2011)] that there exist quantum channels where a single use cannot transmit classical information perfectly yet two uses can. This phenomenon is called the superactivation of the zero-error classical capacity which does not occur in classical channels. In this paper, it is shown that qubit channels cannot generate the superactivation.