Entanglement of a two two-level atom interacting with electromagnetic field in the presence of converter terms

The exact solution of the problem of two two-level atoms interacting with a two-mode radiation field in the presence of a parametric converter term is presented. More precisely we have considered a Hamiltonian model that includes two types of interaction: one is the field–field (frequency converter type) and the other is the atom–field interaction. By introducing a canonical transformation an exact solution of the wave function in the Schrödinger picture is obtained. The result presented in this context is used to discuss the atomic inversion as well as the entropy squeezing and variance squeezing phenomena. We use the von Neuman entropy to measure the degree of entanglement between the atom and the field. These aspects are sensitive to changes in the converter parameter.