Entanglement degree of a nonlinear multiphoton Jaynes-Cummings model

We extend our earlier investigations (Furuichi S and Abdel-Aty M 2001 J. Phys. A: Math. Gen. 34 6851) on the entanglement degree of a two-level atom to include any forms of nonlinearitics of both the field and the intensity-dependent atom-field coupling. We present a derivation of the unitary operator within the frame of the dressed state approach, by means of which we identify and numerically demonstrate the region of parameters where significantly large entanglement can be obtained. The influences of the nonlinearity, Stark shifts and detuning on the degree of entanglement are examined. It is shown that features of the degree of entanglement are influenced significantly by the kinds of nonlinearity of the single-mode field. The model presented in this paper can be regarded as a generalization of the Jaynes-Cummings model.