Agenda

Résumé : Macroscopic quantum coherence emerges in fluids such as Bose-Einstein condensates, where a significant fraction of the particles share the same wave function. Superfluidity describes the rigidity of a gas or a liquid when we try to set it in motion. Although the two phenomena are often linked, they are not equivalent. In this lecture, I will use recent experiments with quantum gases to show that we can have a superfluid system with no long-range coherence, and conversely a fully coherent system with only a small superfluid fraction.