“…In contrast, considering the novel optomechanical setups that exhibit strong single-photon coupling, e.g. ones involving ultracold atoms [13,14] or hybrid devices achieving non-linearity by employing an auxiliary system [35][36][37][38], but also anticipating their advent within other platforms [39], one must return to the exact solutions of system dynamics [7,8] that, however, are analytically tractable only if particular limited forms of decoherence and optical driving are accounted for [40] -unless one resorts to numerical methods [41,42]. Importantly, it is the non-linear effects that allow a single photon to be converted into multiple phonons and vice versa, so that phenomena such as blockades [43,44] or cascades [45] of photons become then possible, with the light leaving the cavity exhibiting a clear non-classical character [46].…”