Effects of the radiation field on collapse and revival phenomena in a four-level system

The effect of the detuning on the collapse and revival of some quantum statistical properties, (such as mean photon number and Mandelʹs Q parameter), are investigated by considering the interaction of a four-level atomic system with a single-mode radiation field, when the atom is initially prepared in a coherent superposition of the upper excited state and the ground state and the field initially in a coherent state. It is found that, for off-resonance case, the detuning between the field and the atom has a significant influence on the collapse and revival phenomenon which leads to the emergence of collapse and revival with a small initial mean photon number ñ=1. The revival time has been calculated. Numerical computations and discussion of the results are presented.