Entanglement on macroscopic scales in a resonantly laser-excited atomic ensemble

TL;DR

This paper demonstrates that two spatially separated groups of atoms in a weak resonant laser field can become entangled, with the degree of entanglement depending on their size and separation, even on a macroscopic scale.

Contribution

It provides a theoretical analysis of entanglement between distant atomic groups in a dilute regime under resonant laser excitation, revealing conditions for entanglement based on size and separation.

Findings

Maximum entanglement negativity decreases with distance

Entanglement increases with group size

Large enough groups are necessarily entangled at given laser intensity

Abstract

We show that two groups of slow two-level atoms in a weak resonant laser field, are entangled. The considered groups can be separated by a macroscopic distance, and be parts of a larger atomic ensemble. In a dilute regime, for two very distant groups of atoms, in a plane wave laser beam, we determine the maximum attainable entanglement negativity, and a laser intensity below which they are certainly entangled. They both decrease with increasing distance between the two groups, but increase with enlarging groups sizes. As a consequence, for given laser intensity, far separated groups of atoms are necessarily entangled if they are big enough.