Entangled Dark States from Superradiant Dynamics in Multilevel Atoms in a Cavity

Recent years have witnessed a staggering progress in the control and manipulation of quantum matter for quantum sensing, simulation, and computation. Although so far most of the research has been focused on isolating a pair of internal levels (a qubit) to realize two-level quantum systems, the physics of multilevel atoms is beginning to attract much attention thanks to recent advances in experiments with ultra-cold atoms. In this talk, we will show that in fact systems of multilevel atoms can open untapped opportunities for exploring rich many-body dynamics and creating entangled states of matter useful for quantum technological applications. In particular, we will focus on the collective dissipative decay of multilevel atoms inside cavities, a system that is considerably richer than the case of two-level atoms due to the existence of multiple decay channels and the coupling to two polarization modes of the cavity light. Despite the complexity, we will report it is possible to find regimes where the many-body dynamics can be understood, sometimes even at an analytical level. Interestingly, in contrast to two-level atoms, multilevel atoms can harbour eigenstates that are perfectly dark to cavity decay even within the subspace of permutationally symmetric states. The dark states arise from destructive interference between different internal transitions and are entangled. Furthermore, we will explain how these states can be controlled and manipulated via an external drive and transformed into spin squeezed states that can remain entangled even after the drives are turned off.

These predictions should be experimentally observable in current optical cavity experiments operating with alkaline-earth atoms or with engineered Raman-dressed transitions, opening up a number of exciting research directions including dissipative preparation of entangled dark states of matter, which are resilient to collective decay, and thus useful for quantum sensing, and for storage of quantum information.