  Hybrid interactions between light and two-level systems and their nonlinear
nature are crucial components of advanced quantum information processing and
quantum networks. Rabi interaction exhibits the hybrid nonlinear nature, but
its implementation is challenging at optical frequencies where the rotating
wave approximation (RWA) is valid. Here, we propose a setup to conditionally
induce Rabi interaction between discrete variable and continuous variable of
traveling beams of light. We show that our scheme can generate Rabi interaction
on weak states of light, where signatures of the nonlinear quantum effects are
preserved for typical experimental losses. These results prove that a hybrid
Rabi interaction can be realized in all-optical setups, and open a way to
experimental investigations of nonlinear quantum optics beyond RWA.
