K模辅射场与二能级原子作用系统中场熵的演化

利用时间演化算符方法研究了K模相干光场与二能级原子相互作用系统中系统态矢的演化.利用数值计算方法研究了三模相干光场与二能级原子相互作用系统中场熵的演化,讨论了初始光场强度对场熵演化的影响.结果表明:当初始光场较强时,场熵随时间的演化呈现出规则的振荡,光场与原子之间的相互作用主要表现为双光子跃迁过程.     

依赖强度耦合多光子过程中的缠绕与薛定谔猫态

通过研究领事强度耦合多光子过程中的光场熵演化和光场Ｑ函数，揭示了光场与原子的缠绕特性，讨论原子跃迁过程中吸收或发射的光子数对缠绕特性和薛定谔猫态的影响。     

NPS态光场与运动二能级原子相互作用系统的保真度

利用全量子理论计算方法,研究NPS态光场与运动二能级原子相互作用系统和光场保真度的时间演化规律,分析原子初态、最大光子数、光场参量、原子运动速度、场模结构参量和跃迁光子数对系统和光场保真度的影响.结果表明:最大光子数越大或光场参量越小,保真度平均值越低;原子运动速度或场模结构参量增大保真度变大,振荡频率加快;跃迁光子数增大时,保真度周期性或无规则振荡;当原子初态处于叠加态时系统和光场保真度最大,且振荡规律相同.     

与光场依赖强度耦合多光子通道中原子周期量子回声的产生和控制

研究了与光场依赖强度耦合多光子通道中原子态保真度演化,探讨了原子周期量子回声的产生和控制。通过分别考察原子相干分布角、光场平均光子数以及原子跃迁时吸收（或发射）的光子数对原子态保真度演化的影响,获得了产生和控制原子周期量子回声的系统参数,并揭示了原子态高保真输出的物理实质。     

与光场依赖强度耦合多光子通道中原子周期量子回声的产生和控制

研究了与光场依赖强度耦合多光子通道中原子态保真度演化,探讨了原子周期量子回声的产生和控制。通过分别考察原子相干分布角、光场平均光子数以及原子跃迁时吸收（或发射）的光子数对原子态保真度演化的影响,获得了产生和控制原子周期量子回声的系统参数,并揭示了原子态高保真输出的物理实质。     

耗散腔中多光子J-C模型中的密度算符间距

研究了腔场存在相位耗散时多光子J-C模型中光场、原子和系统的密度算符间距;讨论了原子初始态、光场强度以及腔场耗散系数对密度算符间距的影响;且比较了不同跃迁光子数下体系的密度算符间距.结果发现:①密度算符间距与原子的初始态密切相关.②光场和系统的密度算符间距在耗散腔中作减幅周期振荡最终达到稳定,达到稳定所需时间随腔的耗散系数增大而缩短;而原子的密度算符间距与腔的耗散无关.③随着光场初始强度的增加,光场和系统与各自初始态的偏离程度增大.④对于双光子跃迁,当腔场存在相位损耗时光场和系统的密度算符间距仍作减幅周期振荡,原子仍周期性的回到纯态.但由于光场与原子的纠缠和退纠缠速率加快,密度算符间距在每个周期内振荡加剧.     

光场与Ⅴ型三能级原子依赖强度耦合系统场熵的演化特性

研究了光场与v型三能级原子依赖强度耦合系统场熵的演化特性,讨论了单光子跃迁失谐量和初始光子数对场熵演化的影响.研究结果表明,当失谐量比较小且初始光场较弱时,场熵的时间演化行为与单光子JaynesCummings模型相似;当失谐量足够大或初始光场足够强时,场熵的时间演化表现出类似于双光子Jaynes-Cummings 模型中场熵演化的周期性.     

光场与V型三能级原子依赖强度耦合系统场熵的演化特性

研究了光场与V型三能级原子依赖强度耦合系统场熵的演化特性,讨论了单光子跃迁失谐量和初始光子数对场熵演化的影响. 研究结果表明,当失谐量比较小且初始光场较弱时,场熵的时间演化行为与单光子Jaynes-Cummings模型相似; 当失谐量足够大或初始光场足够强时,场熵的时间演化表现出类似于双光子Jaynes-Cummings模型中场熵演化的周期性.     

Bell态原子与双模纠缠相干光场双光子相互作用系统的量子纠缠

运用全量子理论和数值计算的方法,借助于原子的量子约化熵研究了初始处于Bell态|β00>和| β10>的两原子与双模纠缠相干光场双光子相互作用系统中两原子与双模光场之间纠缠的演化特性.分析了光场强度、光场纠缠度及原子间相互作用强度对原子熵演化特性的影响.结果表明:随着双模光场的平均光子数的增大,原子熵的时间演化曲线逐渐变为规则振荡;增大原子间的相互作用强度,原子熵的振荡频率和振幅都减小;改变双模光场的纠缠度,原子熵的振荡频率和振幅都不发生改变.     

克尔介质中皮秒亮孤子多光子J-C模型粒子数反转特性

利用全量子理论研究了克尔介质中皮秒孤子光场与二能级原子多光子相互作用系统中粒子数反转随时间的变化特性,用MATLAB软件编程模拟并讨论了初始平均光子数、克尔介质与场模非线性相互作用强弱、孤子光场与原子耦合强度及相互作用过程中跃迁光子数目对粒子数反转的影响.数值计算结果表明：初始平均光子数越大、克尔介质与场模的非线性相互作用越强、孤子光场与原子耦合强度越小或相互作用过程中跃迁光子数目越多,粒子数反转崩坍与恢复的振荡幅度越小、平均值越大.     

Resonance fluorescence of a two-level atom in a feedback loop

The resonance fluorescence spectrum of a two-level atom in a classical light field, whose phase is changed by a feedback system by π after the detection of each spontaneous photon, has been calculated. The spectrum resembles the well-known Rautian-Mollow triplet. However, the sidebands become sharply asymmetric at a nonzero frequency detuning of the light field from the atomic resonance transition. In addition, the spectrum retains the pronounced triplet shape even beyond the secular approximation, when the sidebands of the Rautian-Mollow structure become unresolved in the absence of the feedback.     

Cooperative two-photon resonance fluorescence of a three-level atom

We have calculated the Green function describing the physical process where a three level atom interacts with a strong pump field as well as with a weak perturbing signal field in the limit of high photon densities. The theory is then used to describe the cooperative two-photon resonance fluorescence which occurs when the sum of the two atomic transition frequencies is nearly twice the frequency of the pump field. Our atomic system is equivalent to a two-level atom when the degeneracy of the ground state is removed by a Stark field. The excitation spectrum has been found to consist of new bands and sidebands which exist only in the presence of the Stark field. The resonance process which occurs when the Stark splitting is in the neighbourhood of the energy shift induced by the laser field has been discussed in detail.     

非线性光子晶体中原子辐射光场的非经典性质

讨论了非线性光子晶体微腔中二能级原子在相干场驱动下腔场的频谱特性及光子的统计性质.研究结果表明,当光子晶体的态密度很大时,如果腔场模与原子共振荧光Mollow峰的中心峰共振,则腔场的涨落压缩到量子散弹噪声之下,且与线性光子晶体微腔的情况相比其谱线峰值变大.当驱动场频率较大时光子服从亚Poisson分布,且非常接近Poisson分布.     

非线性光子晶体中原子辐射光场的非经典性质

讨论了非线性光子晶体微腔中二能级原子在相干场驱动下腔场的频谱特性及光子的统计性质.研究结果表明,当光子晶体的态密度很大时,如果腔场模与原子共振荧光Mollow峰的中心峰共振,则腔场的涨落压缩到量子散弹噪声之下,且与线性光子晶体微腔的情况相比其谱线峰值变大.当驱动场频率较大时光子服从亚Poisson分布,且非常接近Poisson分布. 关键词： 光子晶体 参量振荡 非弹性谱 二阶相关函数     

One- and two-photon resonance fluorescence of a three-level atom at high photon densities

We consider the possible physical processes that may arise in a three-level atom when only two of its levels interact with a strong electromagnetic field and when the atomic transition frequency is nearly equal to once and twice the frequency of the laser field, respectively. There have been found pronounced cooperative effects in the spectrum of the two-level system, which is in resonance with the laser field, arising from the presence of the third level. The excitation spectra describing the transitions from the first excited state into the second excited state and from that to the ground state consist, apart from the two central peaks, of two pairs of sidebands which are induced by the laser field of the neighbouring system. Detailed expressions of the spectral functions for the physical processes of one- and two-photon resonance fluorescence have been derived and discussed in the limit of high photon densities. The excitation spectrum of the low frequency modes has been considered and discussed in detail. It is found that quantum beats in spontaneous emission may appear in the spectra of the one- and two-photon resonance fluorescence arising from the interference between the two atomic transition frequencies and the frequency of the laser field. The importance of the low frequency modes that occur in the processes in question has been pointed out.     

Single photon transport properties in coupled cavity arrays nonlocally coupled to a two-level atom in the presence of dissipation

We discuss the effects of dissipation on the behavior of single photon transport in a system of coupled cavity arrays,with the two nearest cavities nonlocally coupled to a two-level atom.The single photon transmission amplitude is solved exactly by employing the quasi-boson picture.We investigate two different situations of local and nonlocal couplings,respectively.Comparing the dissipative case with the nondissipative one reveals that the dissipation of the system increases the middle dip and lowers the peak of the single photon transmission amplitudes,broadening the line width of the transport spectrum.It should be noted that the influence of the cavity dissipation to the single photon transport spectrum is asymmetric.By comparing the nonlocal coupling with the local one,one can find that the enhancement of the middle dip of single photon transmission amplitudes is mostly caused by the atom dissipation and that the reduced peak is mainly caused by the cavity dissipation,no matter whether it is a nonlocal or local coupling case.Whereas in the nonlocal coupling case,when the coupling strength gets stronger,the cavity dissipation has a greater effect on the single photon transport spectrum and the atom dissipation affection becomes weak,so it can be ignored.     

Study of Some Properties of Two-Level Atom in Quantum Optics

With the concept of negative photon and the K-photon J C model, we investigate analytically the effect of virtual photon field on the collapse revival effect of atomic inversion and squeezing of atom, we find that there is a significant effect of virtual photon field on atomic inversion and squeezing of atom; with the one-photon model as an example, we find that the squeezing of atom occurs periodically, the time and times of squeezing are only related to the resonance frequency and the amplitude of squeezing related to coupling constant of atom field, mean photon number and resonance frequency; also we show that the effect of squeezing of atom does not exist within rotating wave approximation if K≥3. Taking the approach of nearest-neighboring spectrum in the quantum chaos field, we investigate the properties of energy spectrum in one-photon JC model and show that the integrable region,non-integrable region and transition region of this system can be illustrated by a phase diagram;also we discuss the influence of interaction of atoms on spectrum and Δ₃ statistics of adjacent energy levels, we find that the influence of interaction is little obvious in strong field but takes great important role in weak field.     

Two-photon resonance fluorescence

The excitation spectrum of a two-level atom interacting with a strong electromagnetic field is considered when the atomic transition frequency is nearly twice the frequency of the laser field. The spectral function consists of four Lorentzian lines describing: the central line peaked near the two-photon resonance, two sidebands peaked at the high and low frequency regions respectively and the one-photon frequency mode. In the limit of high photon densities, the low frequency photon mode is induced by the pump field which removes the singularity occurring at the two-photon resonance frequency.