Improvement in quantum communication using quantum switch

TL;DR

This paper explores how the quantum switch can enable useful communication through channels that are otherwise useless, enhancing quantum communication tasks and coherence preservation, with considerations on noise effects.

Contribution

It demonstrates that quantum switch can turn useless channels into useful ones for communication and discusses strategies to optimize this advantage.

Findings

Quantum switch enables communication through otherwise useless channels.

Concatenating channels with the switch can restore usefulness.

Noise in the switch reduces its communication advantage.

Abstract

Applications of the quantum switch on quantum channels have recently become a topic of intense discussion. In the present work, we show that some useless (for communication) channels may provide useful communication under the action of quantum switch for several information-theoretic tasks: quantum random access codes, quantum steering, etc. We demonstrate that the quantum switch can also be useful in preventing the loss of coherence in a system when only coherence-breaking channels are the available channels for communication. We also show that if a useless quantum channel does not provide useful communication even after using a quantum switch, concatenating the channel with another suitable quantum channel, and subsequently using the switch, one may achieve useful communication. Finally, we discuss how the introduction of noise in the quantum switch can reduce the advantage that the switch provides.