Two-level atom witness of thermalization of multimode optical fibers

In the present project, we study the dynamics of the two-level system coupled with the multimode optical system. In particular, we considered a square lattice of optical fibers. We aimed to answer whether we can infer information about the thermalization of optical modes through the thermalization of two-level atoms. After averaging over the set of modes, the dynamic of the two-level system is free of quantum revivals, and that is the signature of thermalization. We showed that the temperature of the two-level system increases with the temperature of optical modes and mean photon number. In the high-temperature limit of optical modes, the temperature of the two-level system tends to be infinity, and level populations are equal.