Gaussian entanglement in the turbulent atmosphere

TL;DR

This paper rigorously analyzes how atmospheric turbulence affects Gaussian entanglement in quantum states, revealing how local displacements and squeezing can optimize entanglement transfer for free-space quantum communication.

Contribution

It provides a theoretical framework for understanding and optimizing Gaussian entanglement transmission through turbulent atmospheric channels, including a protocol for long-distance transfer.

Findings

Entanglement depends non-trivially on input displacements.

Optimal local squeezing can enhance entanglement certification.

A protocol for arbitrary-distance entanglement transfer is proposed.

Abstract

We provide a rigorous treatment of the entanglement properties of two-mode Gaussian states in atmospheric channels by deriving and analyzing the input-output relations for the corresponding entanglement test. A key feature of such turbulent channels is a non-trivial dependence of the transmitted continuous-variable entanglement on coherent displacements of the quantum state of the input field. Remarkably, this allows one to optimize the entanglement certification by modifying local coherent amplitudes using a finite, but optimal amount of squeezing. In addition, we propose a protocol which, in principle, renders it possible to transfer the Gaussian entanglement through any turbulent channel over arbitrary distances. Therefore, our approach provides the theoretical foundation for advanced applications of Gaussian entanglement in free-space quantum communication.