Quantum Coherence In Three-level System Driven By Cross Talk

We establish the Λ type three-level system model with coupling field cross talk. It isbased on the previous related research of the field of multilevel system. The thesis presents atheoretical study of the quantum coherence in a Λ type three-level system with theelectromagnetic field cross talk among the two close transition. In semi-classical theorysystem, we analysis the interaction about field and atomic energy level system and get theHamiltonian and the density matrix motion of the system equation. We solve the systemdensity matrix equation of steady state solution by the Floquent method. We put forward thelaw of the probe absorption spectrum with the frequency and the strength of coupling field.Compareing the result of Λ type three-level system, considering the role of cross talk termswith that without it, we analyze the effect of the introduction of the cross term on thedetection of absorption characteristics of the system.Classic Λ type three-level system consists of two ground state energy levels and anexcited state energy level. Coupling field is resonant with corresponding transition. Probeabsorption spectrum is obtained by scanning the transition of the other ground state andexcited state energy level. The two ground state energy levels of the Λ type three-level systemare hyperfine of ground state. Coupling field intersect cross between the hyperfine of groundstates and the excited state energy level transition at the same time. This cross function makethe field and atomic interaction Hamiltonian add a cross terms. This paper analysis the effectof coupling field cross terms on the probe absorption spectrum. The findings shows that underthe effect of a weak Coupling field, the probe absorption spectrum present the EIT, the EITline width increase with coupling field cross talk. With the increase of coupling field Rabifrequency, space between absorption peak in probe absorption spectrum increase, formingA-T double peak. The location of two peaks is symmetrical about the resonant with probetransition, the space between peaks increase with coupling field Rabi frequency. If youconsider approximatly coupling field cross take have the same Rabi frequency on transitions,the two peaks locate in212respectively; The space of two peak is21. When there is detuning of the coupling field, the peak value of probe absorption spectrum shift, theshift is associate with the size of detuning of the coupling field. With the increase of detuningof the coupling field, one side of absorption peak gradully get close to the resonant with probetransition, the other side of absorption peak deviate futher and futher. If we keep the detuningof the coupling field unchanged，the space of two peak grow with the increase of Couplingfield cross terms, but the center location is unchanged, and equals to half of the detuning ofthe coupling field.