Linear entropy and collapse–revival phenomenon for a general formalism N-type four-level atom interacting with a single-mode field

Abstract

In this paper, the linear entropy and collapse–revival phenomenon through the relation ( $$\langle {\hat{a}}^{+}{\hat{a}} \rangle -{\bar{n}}$$ ) in a system of N-configuration four-level atom interacting with a single-mode field with additional forms of nonlinearities of both the field and the intensity-dependent atom-field coupling functional are investigated. A factorization of the initial density operator is assumed, considering the field to be initially in a squeezed coherent states and the atom initially in its most upper excited state. The dynamical behavior of the linear entropy and the time evolution of ( $$\langle {\hat{a}}^{+} {\hat{a}} \rangle -{\bar{n}}$$ ) are analyzed. In particular, the effects of the mean photon number, detuning, Kerr-like medium and the intensity-dependent coupling functional on the entropy and the evolution of ( $$\langle {\hat{a}}^{+} {\hat{a}} \rangle -{\bar{n}}$$ ) are examined.