Vacuum-induced Berry phase beyond the rotating-wave approximation

With reference to the vacuum-induced Berry phase (VIBP) obtained in the interaction of a spin-1/2 particle with quantized irradiation field under rotating-wave approximation (RWA), we present a completely different treatment for the VIBP by a fully quantum-mechanical treatment beyond the RWA, which gives different definition of the VIBP and indicates the validity of RWA to be relevant not only to the energy conservation and comparison of characteristic parameters, but also to more subtle physics, such as the geometric property of the state evolution. Our result is of conceptual importance and also of significant relevance to quantum-information processing.