Multi-Photon Quantum Rabi Models with Center-of-Mass Motion

Abstract: The precise control of light-matter interaction serves as a cornerstone for diverse quantum technologies, spanning from quantum computing to advanced atom optics. Typical experiments often feature multi-mode fields and require atoms with intricate internal structures to facilitate e.g., multi-photon interactions or cooling. Moreover, the development of high-precision cold-atom sensors necessitates the use of entangled atoms. We introduce a rigorous, second-quantized framework for describing multi-$\Lambda$-atoms in a cavity, encompassing their center-of-mass motion and interaction with a two-mode electromagnetic field. A key feature of our approach is the systematic application of a Hamiltonian averaging theory to the atomic field operators, enabling the derivation of a compact and physically insightful effective Hamiltonian governing the system's time evolution. This effective Hamiltonian not only incorporates the AC-Stark and Bloch-Siegert shifts, augmented by contributions from all involved ancillary states, but also includes effects from counter-rotating terms, offering a more complete description than conventional RWA-based models. A significant finding is the emergence of a particle-particle interaction mediated by ancillary states, stemming directly from the combined quantum nature of the coupled electromagnetic field and atomic system. We illustrate the practical implications of our model through an analysis of atomic Raman diffraction, determining the time evolution for a typical initial state and demonstrating the resulting Rabi oscillations. Furthermore, our results confirm that both the atomic and optical Hong-Ou-Mandel effect can be observed within this Raman configuration, utilizing a specific two-particle input state, thereby extending the utility of Raman diffraction for quantum interference phenomena and providing a microscopic model of the effect.