Effective Dynamics And Photon Blockade Of A Dressed Atom Effected By A Driven Field

The anti-bunching effect (ABE), which marks the quantum feature of light, has been experimentally observed already. It is possible to present ABE for single atom, single quantum dot, or any real single emitter. But in real circumstances, whether bunching, coherence or anti-bunching would occur is under control of complicated reasons. During each excitation circuit, multiple reasons would lead to whether ABE would be presented, such as whether single photon would be obtained from photon pairs, whether the obtained single photon would be emitted, the strength of the driven field and the couple strength of cavity and atom, etc. One of the most obvious results of photon blockade is ABE, which means that photon blockade can be achieved in the linear medium of single atom.In this paper, firstly, a specific analytic analysis about transitions between|ψ+(1)> and |ψ-(3)> caused by multi-photon excitation in cavity QED system is made, using dressed state theory and Frolich transformation. Complicated nonlinearity has been caused when the first photon emits into the system and shifts the energy levels. This is because of the resonance excitation of other photons and the interactions between newly generated energy levels, which lead to more exaggerated energy level shifts. Secondly, the energy spectrums from |ψ+(1)> and |ψ-(3)> are obtained using master equation method, and the image of the extra semiclassical Rabi split is carefully analyzed. The photon correlation function is obtained using quantum regression formula and the master equation. We calculated the second-order correlation function under strong excitation and weak excitation; a more clear expression of photon correlation is obtained after this work. Furthermore, we combine the images of photon correlation function itself, when it is under weak excitation and under strong excitation, and the combination of the above three as a group, to analyze the presentation laws of anti-bunching and bunching under different variables.The conclusions are listed here:Under very weak excitation (ε= 2κ), when the coupling strength is g< 0.0693κ, ABE is presented; 0.0693κ:<g<2.341κ bunching is presented, after that ABE never occurs. Whenε=20κ, coupling strengthg< 66κ, bunching is presented. When 66κ< g<235κ, ABE is presented. When strengthen the field to ε= 60κbunching keeps occurring until g= 600κ. Between 600κ< g< 2110κ ABE is presented. Strong driven of ε= 100κ:, coupling strength between 1650κ～5900κ:, anti-bunching is presented. Other than that, bunching keeps occurring. When ε= 2κ, g= 2κ; ε= 20κ:, ε= 200κ:and ε=100κ,g= 3700κ:we obtained very obvious anti-bunching effect, the images of photon correlation are uncluttered, which makes them good candidates for experimentally presenting the dynamics of this system.