Quantum mutual entropy of a single four-level atom strongly coupled to a cavity field and driven by a laser field

Based on exact quantum dynamics of a single four-level atom strongly coupled to a cavity field mode and driven by a coherent laser field, we investigate quantum mutual entropy as a measure of the amount of total correlations. Through the analysis of the dynamic of the total correlation, we show that under the influence of the decoherence, the total correlation may terminate abruptly in a finite time. Further consequences of our results include a description of total correlations of a general multi-level atomic system.