Abstract:

A number of experiments demonstrated the possibility of observing fascinating quantum effects with continuously probed and pumped atomic ensembles. These experiments deal with collective spin excitations on top of a spin polarized reference state serving as an effective ground state in the space of collective excitations. When collective excitations are generated or probed with CW light a certain degree of CW optical pumping has to be applied compensating probe induced depumping in order to maintain a mean spin polarization. The resulting interplay of continuous probe and pump gives rise to interesting collective dynamics of the atomic spin going well beyond single atom physics in optically dense atomic ensembles. Determining the spin polarized reference state in itself becomes a non-trivial problem of non-equilibrium open-system many-body quantum dynamics. Drawing an analogy to superradiant lasers I will introduce a systematic mean-field treatment taking into account any desired order of n-particle correlations for determining the atomic steady states as well as their two-time correlation functions. I will discuss results for ensembles of Caesium atoms.

Coffee/tea and bread rolls from 10:00