Non-radiative configurations of a few quantum emitters ensembles: evolutionary optimization approach

In this work, we employ differential evolution algorithm to identify the optimal configurations of small atomic ensembles supporting quantum states with maximal radiative lifetime. We demonstrate that atoms mostly tend to assemble in quasi-regular structures with specific geometry strongly depending on the minimal interatomic distance $r_{min}$. We identified the clear underlying physics that governs the suppression of the radiative losses in particular geometries. However, we reveal that the specific configurations in small ensembles are not easily predictable based on the knowledge established for the arrays of large size. In particular, the states that inherit their properties from bound states in continuum in infinite lattices turn out to be the most subradiant in a wide range of $r_{min}$ values. We also show that for small interatomic distance the chains with modulated interatomic distances exhibit fast exponential decrease of the radiative losses with the size of the ensemble.