  This thesis deals with the study of dynamical properties of
out-of-equilibrium quantum systems. We introduce in particular a general class
of Spin-Boson models, which describe for example light-matter interaction or
dissipative phenomena. We contribute to the development of a stochastic
approach to describe the spin dynamics in these models. In this context, the
effect of the bosonic environment is encapsulated into additional stochastic
degrees of freedom whose time-correlations are determined by spectral
properties of the bosonic environment. We use this approach to study many-body
phenomena such as the dissipative quantum phase transition induced by an ohmic
bosonic environment. Synchronization phenomena as well as dissipative
topological transitions are identified. We also progress in the study of arrays
of interacting light-matter systems. These theoretical developments follow
recent experimental achievements, which could ensure a quantitative study of
these phenomena. This notably includes ultra-cold atoms, trapped ions and
cavity and circuit electrodynamics setups. We finally investigate hybrid
systems comprising electronic quantum dots coupled to electromagnetic
resonators, which enable us to provide a spectroscopic analysis of many-body
phenomena linked to the Kondo effect. We also introduce thermoelectric
applications in these devices.
