Field Purification of a General Three-Level System Interacting with Radiation.

In this essay we introduce a new Hamiltonian which represents the interaction between a three-level atom and a single electromagnetic field including arbitrary forms of nonlinearities of both the field and the intensity-dependent coupling. We derive an exact solution for the density operator of the system by means of which we study the field purity for the entangled state of the system. Also, the influences of the nonlinearities on the field purity and mean photon number are examined. Under the condition of an initial coherent field, the field purity shows the collapse-revival phenomenon. It is found that features of these phenomenon are sensitive to the changes of different kinds of the nonlinearities. [ABSTRACT FROM AUTHOR]