Variational analysis of driven-dissipative Rydberg gases

We study the nonequilibrium steady state arising from the interplay between coherent and dissipative dynamics in strongly interacting Rydberg gases using a recently introduced variational method [H. Weimer, Phys. Rev. Lett. 114, 040402 (2015)]. We give a detailed discussion of the properties of this approach and we provide a comparison with methods related to the Bogoliubov-Born-Green-Kirkwood-Yvon hierarchy. We find that the variational approach offers some intrinsic advantages and we also show that it is able to explain the experimental results obtained in an ultracold Rydberg gas on a quantitative level.