Experimental Communication Through Superposition of Quantum Channels

TL;DR

This paper investigates how superposing quantum channels can enhance information capacity, revealing that the capacity increase can be explained by channel expansion to qutrits without requiring superposition.

Contribution

It demonstrates that the capacity enhancement from superposing channels can be understood through channel expansion to qutrits, challenging the necessity of superposition for capacity gains.

Findings

Qutrit channel description explains capacity enhancement.

Superposition is not essential for capacity increase.

Comparison between depolarizing qubit channels and superposed channels.

Abstract

Information capacity enhancement through the coherent control of channels has attracted much attention of late, with work exploring the effect of coherent control of channel causal orders, channel superpositions, and information encoding. Coherently controlling channels necessitates a non-trivial expansion of the channel description, which for superposing qubit channels, is equivalent to expanding the channel to act on qutrits. Here we explore the nature of this capacity enhancement for the superposition of channels by comparing the maximum coherent information through depolarizing qubit channels and relevant superposed and qutrit channels. We show that the expanded qutrit channel description in itself is sufficient to explain the capacity enhancement without any use of superposition.