Gegg, MichaelCarmele, AlexanderKnorr, AndreasRichter, Marten2022-02-172022-02-172018-01-05https://depositonce.tu-berlin.de/handle/11303/16425http://dx.doi.org/10.14279/depositonce-15201Collectivity in ensembles of atoms gives rise to effects like super- and subradiance. While superradiance is well studied and experimentally accessible, subradiance remains elusive since it is difficult to track experimentally as well as theoretically. Here we present a new type of phase transition in the resonantly driven, open Dicke model that leads to a deterministic generation of subradiant states. At the transition the system switches from a predominantly superradiant to a predominantly subradiant state. Counterintuitively, the cavity decay is the crucial parameter for subradiant state generation and not the individualizing process of spontaneous decay. The observed effect is thus a cavity assisted generation of subradiant quantum coherences. Clear experimental signatures for the effect are presented and entanglement properties are discussed. Letting the system relax into the ground state generates a cascade of dark Dicke states, with dark state populations up to unity. Furthermore we introduce a collectivity measure that allows to quantify collective behaviour.en530 PhysikDicke modelcollective effects in quantum opticssuperradiance and subradiancequantum entanglementspecific phase transitionsArticle2022-02-111367-2630