  Catalysis plays a key role in many scientific areas, most notably in
chemistry and biology. Here we present a catalytic process in a paradigmatic
quantum optics setup, namely the Jaynes-Cummings model, where an atom interacts
with an optical cavity. The atom plays the role of the catalyst, and allows for
the deterministic generation of non-classical light in the cavity. Considering
a cavity prepared in a ``classical'' coherent state, and choosing appropriately
the atomic state and the interaction time, we obtain an evolution with the
following properties. First, the state of the cavity has been modified, and now
features non-classicality, as witnessed by sub-Poissonian statistics or Wigner
negativity. Second, the process is catalytic, in the sense that the atom is
deterministically returned to its initial state exactly, and can be re-used
multiple times. What is more, we also show that our findings are robust under
dissipation and can be applied to scenarios featuring cavity loss and atomic
decay. Finally, we investigate the mechanism of this catalytic process, in
particular highlighting the key role of correlations and quantum coherence.
