Effets de cohérence en diffusion multiple de la lumière et intrication des états cohérents

Abstract

This work is devoted on the one hand to the investigation of coherence effects in multiple scattering of light by an atomic cloud and on the other hand to the entanglement of a deformed coherent states. The interaction b etween light and a dilute disordered atomic cloud gives rise to collective coherent effects due to the interaction of the induced dip oles via the external field. The behavior of such coherent effects in multiple scattering regime is an important question for various physical systems. We present two theoretical models describing those coherence effects in different scattering regimes. The scattering order expansion treatment of light scattering allows us to highlight the role of the first and second scattering orders as well as the interference between the resulting scattered fields. In the multiple scattering regime we show that the radiation pressure force is not a good observable to probe cooperative effects. Furthermore, we discover a surprising phase coherence that hints that collective effects may survive in multiple scattering regime. That could be due to a synchronization between the induced atomic dipoles. In a second part, we study the effect of an algebra deformation on entangled coherent states. Such an approach allows to describe decoherence in perturbed entangled quantum systems. We construct a deformed coherent states and calculate their concurrence. We show that algebra deformation could have a non negligible impact on bipartite entangled coherent states if those later are not maximally entangled.