Operator Approach to Atom–Field Interactions:

P. R. Berman, Vladimir S. Malinovsky

Michael Fleischhauer

The interaction of a quantized field mode with N identical atoms coupled to individual reserviors and classical driving fields is studied. An effective time-evolution operator for the radiation mode is derived. The exponent of this operator can be written as the number of atoms times an infinite sum containing field operators and correlation functions of freely evolving (no atom-field coupling) single-atom operators. In the adiabatic limit of fast decaying atomic correlations one can derive a master equation for the field density matrix. It is shown that the Liouvillian describing the interaction of the field mode with the N atoms is N times the single-atom Liouvillian.

HE Shu-fang

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.

Ravinder Rupchand Puri

Ming Li, SUN JIU-XUN, 电子科技大学物理电子学院,成都 610054

The Hamiltonian operator of a system of single-mode light field interacting with Bose-Einstein condensate (BEC) of two-level atoms is discussed in terms of the lattice-liquid model. It is indicated that the contribution of the interaction between atoms to the Hamiltonian was irrationally overestimated in the literature, so the Hamiltonian operator is improved in the present paper. Based on the improved Hamiltonian, the equations of motion of the photon and atomic operators are derived analytically. The relevant parameters in the model are estimated in connection with the BEC experimental conditions. The influence of the interaction between atoms in the BEC on the squeezing of light field and the atomic lasers is studied. The results show that the dependence of squeezing factor with atom number in BEC is different from that given in literature. and the fluctuations of two quadrature components of light evolve periodically with cosine law and the fluctuations of two quadrature components of the atomic laser can be squeezed.