Channel capacity of relativistic quantum communication with rapid interaction

TL;DR

This paper investigates the maximum information transmission capacity in relativistic quantum communication using rapid, delta-coupled detector interactions, showing the equivalence and optimality of different nonperturbative methods.

Contribution

It demonstrates that rapid delta-coupling interactions can achieve channel capacities comparable to gapless detector models and proves their equivalence and optimality in relativistic quantum communication.

Findings

Delta-coupling interactions can match the capacity of gapless detector models.

The channel capacity derived from delta-coupling is proven to be optimal.

Both nonperturbative methods yield essentially the same channel capacity.

Abstract

In this work we study nonperturbatively the transmission of classical and quantum information in globally hyperbolic spacetimes, where the communication channel is between two qubit detectors interacting with a quantized massless scalar field via delta-coupling interaction. This interaction approximates very rapid detector-field interaction, effectively occurring at a single instant in time for each detector. We show that when both detectors interact via delta-coupling, one can arrange and tune the detectors so that the channel capacity is (at least) as good as the quantum channel constructed nonperturbatively using \textit{gapless detectors} by Landulfo [PRD 93, 104019]. Furthermore, we prove that this channel capacity is in fact optimal, i.e., both nonperturbative methods give essentially the same channel capacity, thus there is a sense in which the two methods can be regarded as equivalent as far as relativistic quantum communication is concerned.