He began his doctoral studies under Peter Zoller, which he finished in 1989 with the dissertation "Atomic Dynamics in Classical Stochastic and Quantum Light Fields".

Along his colleagues, he has developed the notion of self-organization of atoms interacting strongly with quantized radiation fields of high-Q cavities,[7][8] as a manifestation of the Dicke superradiant phase transition.

This phenomenon has been observed in many experiments, ranging from Bose-Einstein condensates[9] to non-interacting[10] and strongly interacting[11] Fermi gases.

The atomic self-organization in cavities is currently an active field of research, with the prospect to address some of the most challenging, open questions in nonequilibrium many-body physics in a controlled way.

QuantumOptics.jl is being developed in Helmut Ritsch's CQED group at the Institute for Theoretical Physics of the University of Innsbruck since 2017, with the 1.0 version being released in July 2021.