Asier Piñeiro Orioli
We investigate the collective decay dynamics of atoms with a generic multilevel structure F -> F' coupled to two light modes of different polarization inside a cavity. Due to the multiple decay channels, the eigenstate structure and superradiant behavior is much richer and more complex than for two-level atoms. In particular, we find that, in contrast to the two-level case, multilevel atoms can harbour eigenstates that are perfectly dark to cavity decay even within the subspace of permutationally symmetric states (collective Dicke manifold). As a consequence, the superradiant decay of multilevel atoms can end up stuck in one of these dark states, where a macroscopic fraction of the atoms remains excited. These dark states should be readily observable in current setups of optical cavity experiments with alkaline-earth atoms or Raman-dressed transitions. Their long-lived nature further anticipates potential applications in quantum sensing and metrology, and quantum simulation. Specifically, the ubiquity of dark states in such multilevel systems opens exciting research directions for the generation of long-lived entangled states of matter or new driven-dissipative phases with multiple steady-states.