Emergent dark states from superradiant dynamics in multilevel atoms in a cavity

TL;DR

This paper explores how multilevel atoms in a cavity can form dark states through destructive interference, leading to entangled states that remain excited and could be useful for quantum technologies.

Contribution

It reveals the existence of dark states in multilevel atoms within a cavity, a phenomenon not present in two-level systems, and discusses their potential applications.

Findings

Multilevel atoms can host eigenstates that are dark to cavity decay.

Dark states are formed by destructive interference between internal transitions.

Superradiant decay can result in atoms remaining in entangled dark states.

Abstract

We investigate the collective decay dynamics of atoms with a generic multilevel structure (angular momenta $F\leftrightarrow F'$) coupled to two light modes of different polarization inside a cavity. In contrast to two-level atoms, we find that multilevel atoms can harbour eigenstates that are perfectly dark to cavity decay even within the subspace of permutationally symmetric states (collective Dicke manifold). The dark states arise from destructive interference between different internal transitions and are shown to be entangled. Remarkably, 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. This opens the door to the preparation of entangled dark states of matter through collective dissipation useful for quantum sensing and quantum simulation. Our predictions should be readily observable in current optical cavity experiments with alkaline-earth atoms or Raman-dressed transitions.