Improvement in quantum communication using quantum switch

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.

Automated summary

Applications of the quantum switch on quantum channels have been a hot topic. In this work, we find that some useless channels can provide useful communication under the action of a quantum switch for tasks like quantum random access codes and quantum steering. We also demonstrate the usefulness of the quantum switch in preventing coherence loss when only coherence-breaking channels are available. Furthermore, we show that by concatenating a useless channel with another suitable quantum channel and subsequently using the switch, useful communication can be achieved.