Evolution of the Distance of Density Operators of Field-atom Interacting System in a Medium Cavity

Abstract

By using the distance of density operators(DDO),we pay attention to the information differences between the field and the atom subsystems in the interacting system combined by a uncorrelated two-mode coherent field and a V-type three-level atom in a cavity filled with a Kerr-like medium is researched in the paper.Through numerical calculation and picture methods,the influence of initial states of the atom and Kerr strength on the DDO time-dependent evolution of the whole system as well as that of the two subsystems is discussed and the results show that: First,in the Absent of kerr-like medium,for arbitrary initial states of the atom(i.e.excited and basis state),the DDO evolution of the system and atom present collapse and revival phenomenon.Second,with the increase of the Kerr strength,(1) when atom is in excited state initially,the DDO evolution of the atom and field present periodic change,and the larger the Kerr strength is the clearer the periodicity is.(2) When atom is in basic state initially,the DDO evolution of the atom approaches a line,the final state of the atom remains unchangable approximately during the interacting time,but the DDO evolution of the field is oscillating all the time.Finally,in the two initial conditions(i.e.the atom is in excited and ground states),with the Kerr strength increasing,the DDO of the atom is decreasing,it is to say that the atom is prefer to staying in initial state,and that reflects the trapped effects of Kerr-like medium;the DDO of the field become larger,the distance between the initial and final state of the field becomes farther,this case is due to the interaction of the field and Kerr-like medium;the DDO evolution of the whole system maintain oscillating at the unity(i.e.orthogonal state) hereabout.