Does the Berry phase in a quantum optical system originate from the rotating wave approximation?

•Non-zero Berry phases for the Rabi model (without rotating wave approximation) are verified.•A general formulation of Berry phases for both the JC model and the Rabi model is presented.•The claim of vanishing Berry phase in the Rabi model is a result of improper semiclassical approximation.•Analytic solutions for the Rabi model is presented in the semiclassical approximation.

The Berry phase (BP) in a quantized light field demonstrated more than a decade ago (Fuentes-Guridi et al., 2002 [9]) has attracted considerable attention, since it plays an important role in the cavity quantum electrodynamics. However, it is argued in Larson (2012) [15] that such a BP is just due to the rotating wave approximation (RWA) and the relevant BP should vanish beyond this approximation. Based on a consistent analysis we conclude in this letter that the BP in a generic Rabi model actually exists, no matter whether the RWA is applied. The existence of BP is also generalized to a three-level atom in the quantized cavity field.