Light-matter micro-macro entanglement

TL;DR

This paper reports the observation of light-matter micro-macro entanglement involving a single photon and a large atomic ensemble, advancing understanding of quantum phenomena at macroscopic scales.

Contribution

It demonstrates the creation and certification of a superposition state with macroscopically distinguishable atomic components, using quantum memory techniques.

Findings

Successful observation of photon-atom entanglement

Creation of superpositions with tens of atomic excitations

Potential for expanding macroscopic quantum states in matter

Abstract

Quantum mechanics predicts microscopic phenomena with undeniable success. Nevertheless, current theoretical and experimental efforts still do not yield conclusive evidence that there is, or not, a fundamental limitation on the possibility to observe quantum phenomena at the macroscopic scale. This question prompted several experimental efforts producing quantum superpositions of large quantum states in light or matter. Here we report on the observation of entanglement between a single photon and an atomic ensemble. The certified entanglement stems from a light-matter micro-macro entangled state that involves the superposition of two macroscopically distinguishable solid-state components composed of several tens of atomic excitations. Our approach leverages from quantum memory techniques and could be used in other systems to expand the size of quantum superpositions in matter.