摘要
Buck-Sukumar (BS)模型在一定的耦合强度处会出现能级塌缩现象.通过引入一个非线性光子项,定义了一个完备的BS模型,消除了能级塌缩.进一步通过计算二阶关联函数等物理量理解了非线性光子项与失谐量对该模型的影响.结果表明,在共振情况下,非线性光子项破坏了BS模型的能谱简谐性,可以在更大的耦合强度范围内产生单光子投影态,形成光子阻塞;而在非共振情况下,非线性光子项使非简谐的能谱在整个耦合区间都有定义,且正失谐促进光子阻塞,负失谐抑制光子阻塞.
The Buck-Sukumar(BS)model,with a nonlinear coupling between the atom and the light field,is well defined only when its coupling strength is lower than a critical coupling.Its energy collapses at a critical coupling and is unbounded beyond that value.In other words,the BS model is incomplete.We introduce a simple and complete BS model by adding a nonlinear photon term into the initial BS model.Considering the rotating wave approximation,this complete BS model conserves the excited number and the parity.By expanding it in the subspace of the product state between the atom and the field,we solve the time-independent Schrödinger equation to obtain the eigenenergy and eigenstate.Furthermore,we explore the influence of the nonlinear photon term on the energy spectrum and the photon blockade effect for the complete BS model by calculating the excited number and second-order correlation function.Our study shows that,the nonlinear photon term not only eliminates the energy spectral collapse but also makes it well-defined and complete in all the coupling regime.When at the resonance between the atomic and the field frequency,the nonlinear photon term breaks the harmonicity of the energy spectrum and produces a ladder of the excited number in the ground state.Because the larger nonlinear photon term inhibits the photon transition from an energy level to the higher one,it produces the single-photon projection state in the larger coupling region.Accordingly,we find that the nonlinear photon term promotes photon blockade by calculating the second-order correlation function.When at the non-resonant region,the nonlinear photon term enlarges the originally anharmonic energy ladder.For a complete BS model with the fixed nonlinear photon coupling strength and the fixed detuning,the energy level for the positive detuning is lower than that with the negative detuning,and more energy is required to overcome the absorption of a photon.Therefore,the positive detuning promotes the photon blockade.For the negative detuning,the system is
作者
刘雪莹
成书杰
高先龙
Liu Xue-Ying;Cheng Shu-Jie;Gao Xian-Long(Department of Physics,Zhejiang Normal University,Jinhua 321004,China)
出处
《物理学报》
SCIE
EI
CAS
CSCD
北大核心
2022年第13期176-182,共7页
Acta Physica Sinica
基金
国家自然科学基金(批准号:12174346,11835011)资助的课题。
