Quantum communication in the presence of a horizon

TL;DR

This paper investigates how an event horizon influences quantum communication between an inertial and an accelerated observer, revealing that the Unruh frequency optimizes signal-to-noise ratio and minimizes conditional variance.

Contribution

It demonstrates that the Unruh frequency acts as a natural cutoff to enhance quantum communication in the presence of a horizon, linking horizon effects with communication optimization.

Findings

Low frequency cutoff maximizes signal-to-noise ratio.

Unruh frequency aligns with optimal cutoff for minimizing conditional variance.

Unruh frequency naturally optimizes quantum communication across horizons.

Abstract

Based on homodyne detection, we discuss how the presence of an event horizon affects quantum communication between an inertial partner, Alice, and a uniformly accelerated partner, Rob. We show that there exists a low frequency cutoff for Rob's homodyne detector that maximizes the signal to noise ratio and it approximately corresponds to the Unruh frequency. In addition, the low frequency cutoff which minimizes the conditional variance between Alice's input state and Rob's output state is also approximately equal to the Unruh frequency. Thus the Unruh frequency provides a natural low frequency cutoff in order to optimize quantum communication of both classical and quantum information between Alice and Rob.