Sending classical information via three noisy channels in superposition of causal orders

TL;DR

This paper explores how classical information can be transmitted through three depolarizing channels arranged in superpositions of causal orders, revealing new behaviors and potential for optimized quantum communication.

Contribution

It introduces the quantum 3-switch as a resource for communication, enabling control over causal orders and uncovering novel information transmission features.

Findings

Non-monotonous information transmission behavior.

Different transmission efficiencies depending on causal order combinations.

Proposed optical implementation for experimental testing.

Abstract

In this work, we study the transmission of classical information through three completely depolarizing channels in superposition of different causal orders. We thus introduce the quantum 3-switch as a resource for quantum communications. We perform a new kind of quantum control that was not accessible to the previously treated two-channel case. The fine and full quantum control achieved using selected combinations of causal orders let us uncover new features: non monotonous behavior on the transmission of information with respect to the number of causal orders involved, and different values of the transmission of information depending on the specific combinations of causal orders considered. Our results are a stepping stone to assess efficiency of coherent quantum control and optimize resources in the implementation of new indefinite causal structures. Finally, we suggest an optical implementation using standard telecom technology to test our predictions.