Nonclassicality and Bell nonlocality in atmospheric links

TL;DR

This paper investigates how atmospheric turbulence affects quantum resources like entanglement and nonlocality in free-space links, and evaluates techniques to preserve these features for quantum communication.

Contribution

It analyzes the impact of atmospheric turbulence on quantum properties and compares methods to maintain nonclassicality in free-space quantum links.

Findings

Atmospheric turbulence degrades quantum entanglement and nonlocality.

Pre-, post-selection, and adaptive techniques can mitigate turbulence effects.

Copropagation of correlated modes offers advantages in free-space quantum communication.

Abstract

Free-space quantum links have clear practical advantages which are unaccessible with fiber-based optical channels --- establishing satellite-mediated quantum links, communications through hardly accessible regions, and communications with moving objects. We consider the effect of the atmospheric turbulence on properties such as quadrature squeezing, entanglement, Bell nonlocality, and nonclassical statistics of photocounts, which are resources for quantum communications. Depending on the characteristics of the given channels, we study the efficiency of different techniques, which enable to preserve these quantum features---post-, pre-selection, and adaptive methods. Furthermore, we show that copropagation of nonclassically-correlated modes, which is used in some communication scenarios, has clear advantages in free-space links.