  We propose a scheme for a quantum thermal machine made by atoms interacting
with a single non-equilibrium electromagnetic field. The field is produced by a
simple configuration of macroscopic objects held at thermal equilibrium at
different temperatures. We show that these machines can deliver all
thermodynamic tasks (cooling, heating and population inversion), and this by
establishing quantum coherence with the body on which they act. Remarkably,
this system allows to reach efficiencies at maximum power very close to the
Carnot limit, much more than in existing models. Our findings offer a new
paradigm for efficient quantum energy flux management, and can be relevant for
both experimental and technological purposes.
