Spectroscopic properties of inhomogeneously broadened spin ensembles in   a cavity
  In large ensembles of identical atoms or spins, the interaction with a mode of the electromagnetic radiation field concentrates in a single superradiant degree of freedom with a collectively enhanced coupling. Given a controllable inhomogeneous broadening, such ensembles may be used for multi-mode storage of quantum states of the radiation field with applications in quantum communication networks and quantum computers. In this paper we analyze how the width and shape of the inhomogeneous broadening influence the collective enhancement and the dynamics of the cavity-ensemble system with focus on the consequences for the ensemble's applicability for quantum information processing tasks. 
Z. Kurucz, J. H. Wesenberg, K. M{\o}lmer
quant-ph