Partitioning of entangling interactions in terms of rotating wave approximation: An approach to the Bell state generation by laser fields

In this paper, we theoretically investigate the entanglement of bipartite or two-mode physical and chemical systems interacting with general static entangling interactions together with external electromagnetic fields. The theoretical method employed is based on the rotating wave approximation (RWA) frequently used in the study on the interaction between systems of interest and electromagnetic fields. We have found that the general entangling interactions can be partitioned into three kinds in terms of RWA. Using the partitioning, we propose one method of creating the Bell states from the initial separable state in the presence of complicated entangling interactions. It turns out that the laser phase affects the relative phase of each basis set of the Bell states. The present work will be useful for the realization of entanglement manipulation in the presence of complicated entangling interactions in molecular systems.