Quantum gases in ring traps: From quantized flows to supersonic rotation

Weakly interacting atomic gases at ultra low temperatures are superfluid. Owing to the high degree of control they offer, these quantum gases give access to a wonderful playground to explore superfluid dynamics. In particular, quantum gases flowing inside waveguides can mimick the behavior of electrons in superconducting circuits, opening the new field of `atomtronics’. The elementary circuit is the ring, where the atomic circulation is expected to be quantized. I will discuss two opposite limits: the production and decay of a small current of a few quanta, and the fast rotation regime where the velocity exceeds the speed of sound.