Here, we present a compact formulation of the resolvent-based theory for calculating atom-photon dressed states built on the idea that the atom behaves as an effective impurity (i). This establishes an explicit connection with the standard impurity problem in condensed matter. When the impurity reduces to a vacancy, the resulting class of dressed states play a central role in the emerging area of topological quantum optics (ii) in that any topologically-robust dressed state is a VDS (iii).
(i) L. Leonforte, D. Valenti, B. Spagnolo, A. Carollo, F. Ciccarello, arXiv:2108.11963
(ii) M. Bello, G. Platero, J. I. Cirac, and A. González-Tudela, Sci. Adv. 5, eaaw0297 (2019)
(iii) L. Leonforte, A. Carollo, F. Ciccarello, PRL 126, 063601 (2021)