高Q腔中原子内态布居对原子平移运动的影响

基于原子作双光子共振跃迁的原子－场缀饰态，讨论了驻波腔场中两能级原子的量子化平移运动与原子内态布居间的相互影响，结果表明原子平移运动敏感地依赖于原子的内态布居，特别当原子处于两内态等权重同相位叠加态时，平移运动呈现出很稳定的特征。     

原子质心运动对Λ型三能级原子动力学行为的影响

研究了由单模腔场驱动的质心做谐振运动的Λ型三能级原子系统,考察了腔场、原子内态及其质心运动线性熵的演化特征,结果表明原子质心运动不仅影响腔场与原子内态线性熵的演化规律而且能够有效地改变两者的关系. 关键词： 原子质心运动 Λ型三能级原子 线性熵     

原子的选择测量对原子纠缠特性和场熵的影响*

考虑初始处于W态的三个二能级原子,将其中两个原子同时注入处于真空态的单模腔中,并与光场发生共振相互作用的情况。采用数值计算方法,通过对是否进行原子态选择性测量情况下,腔内原子间的纠缠性质和场熵的比较,讨论了对腔外原子的态选择性测量对腔内原子间的纠缠性质和场熵演化的影响。研究结果表明：对腔外原子的选择性测量,可增强腔内原子间的纠缠,但会减弱腔內原子与光场的关联。     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

原子与耦合腔相互作用系统中的纠缠特性

研究了耦合腔A和B中各囚禁一个二能级原子的情况,给出了总激发数为2时系统态矢的演化.利用Negativity熵度量两子系统间的纠缠,采用数值计算方法研究了两个原子之间、腔内原子与腔场之间和两个腔场之间的纠缠性质.讨论了腔场间的耦合强度对纠缠特性的影响.研究结果表明:原子1和原子2处于分离态.另一方面,随腔场间耦合系数增大腔场间的纠缠和原子与腔场间的纠缠减小.     

利用原子-腔场共振相互作用制备多原子缠结态

提出了一个利用量子腔场与原子的共振相互作用制备多原子缠结态的方案.首先将一个初态制备在基态和激发态的叠加态的二能级原子注入一个真空态腔场中.原子通过腔时产生原子-场缠结.制备于基态的其它二能级原子分别以不同角度注入腔场,在与腔场相互作用时可制得多原子缠结态,而空腔仍然保持在真空态.与现存的方案比较,该方案在实验上更容易实现.     

利用纠缠交换制备原子-原子最大纠缠态

基于腔量子电动力学(QED)提出一种利用两对纠缠的级联型三能级原子与单模腔场系统制备原子-原子最大纠缠态的简单方案,最初两原子之间、两腔场之间互不纠缠,使其中一个原子与一个腔场发生作用,即纠缠交换,该过程仅需对单个腔场态测量就可实现从未有直接作用的两个原子之间的纠缠,精确控制原子与腔场的相互作用时间可获得具有最大保真度的纠缠态.该方案可以延长腔的有效泄漏时间,从而能有效克服光腔的消相干的影响,这样大大降低了系统对腔的品质的要求.     

原子与光纤耦合腔相互作用系统中的纠缠特性

研究了光纤耦合腔A和B中各囚禁一个和两个二能级原子的情况,给出了总激发数为1时系统态矢的演化。采用Negativity熵来描述两个子系统间的纠缠,利用数值计算方法研究了腔内原子与原子间和腔场与腔场间的纠缠特性,讨论了光纤模与腔场间的耦合强度变化对纠缠特性的影响。另一方面还研究了对腔A中原子选择性测量对纠缠特性的影响。研究结果表明:随光纤模与腔场间的耦合系数增大,腔场间纠缠减弱。原子间纠缠与光纤模与腔场间的耦合系数间存在非线性关系。另一方面,采用原子态选择性测量方法,可增强腔内原子间和腔场间的纠缠。     

二能级原子与双模场喇曼相互作用模型的腔场谱

研究了在高Q腔内二能级原子与双模量子化光场发生双光子共振喇曼相互作用过程的腔场谱.发现原子初态的不同不改变腔场谱结构的基本特征.两模光场初态均为光子数态或均为相干态时,每模腔场谱一般都为双线结构,两条谱线的频差与另一模初始场强大致成正比,改变一模初始场可以调节另一模谱线频率     

运动双原子与腔场作用模型中原子布居的演化

为了找出原子运动对原子布居演化的影响,通过建立两原子在一光学谐振腔中运动的模型,用量子力学分析原子具有不同速度时两原子布居数演化.研究结果表明,当光学腔中光场处于相干态,而原子处于运动中时,两原子的能级布居演化与光学腔场模结构相关联.假如初始时刻原子的位置固定在腔中某一位置,两原子的布居演化在少光子数呈现出周期性,多光...     

Proliferation of atomic wave packets at the nodes of a standing light wave

A quantum analysis is presented of the motion and internal state of a two-level atom in a strong standing-wave light field. Coherent evolution of the atomic wave-packet, atomic dipole moment, and population inversion strongly depends on the ratio between the detuning from atom-field resonance and a characteristic atomic frequency. In the basis of dressed states, atomic motion is represented as wave-packet motion in two effective optical potentials. At exact resonance, coherent population trapping is observed when an atom with zero momentum is centered at a standing-wave node. When the detuning is comparable to the characteristic atomic frequency, the atom crossing a node may or may not undergo a transition between the potentials with probabilities that are similar in order of magnitude. In this detuning range, atomic wave packets proliferate at the nodes of the standing wave. This phenomenon is interpreted as a quantum manifestation of chaotic transport of classical atoms observed in earlier studies. For a certain detuning range, there exists an interval of initial momentum values such that the atom simultaneously oscillates in an optical potential well and moves as a ballistic particle. This behavior of a wave packet is a quantum analog of a classical random walk of an atom, when it enters and leaves optical potential wells in a seemingly irregular manner and freely moves both ways in a periodic standing light wave. In a far-detuned field, the transition probability between the potentials is low, and adiabatic wave-packet evolution corresponding to regular classical motion of an atom is observed.     

边界振动的微腔中的二能级原子

采用全量子理论，对注入腔内的二能级原子、单模腔场和振动边界(视为频率为ω_m的量子谐振子)构成的系统，在相互作用绘景中，求解了该系统的态函数随时间的演化关系，在此基础上得到了原子布居数随时间的演化关系，结果显示布居数在初始值附近振荡，这说明边界的振动是周期性的，它对原子布居数的影响也是周期性的. 关键词： 边界振动的微腔 二能级原子 布居数     

Interaction Dynamics of the External and Internal Degrees of Freedom of an Atom in the Resonant Field of a Standing Light Wave

The theory of the dynamic interaction of the external (translational) and internal (electronic) degrees of freedom of a twolevel atom in the field of a standing light wave in a perfect cavity of the Fabry–Perot type was developed. The theory describes the energy exchange between three subsystems, namely, translational, electronic, and field subsystems, as opposed to the theories of the parametric interaction (in the approximations of Raman–Nath and/or large resonance detuning) and of the atomic motion in free space. In the semiclassical approximation, the corresponding Heisenberg equations of motion were shown to form a closed Hamiltonian dynamic system with two degrees of freedom, namely, translational and collective electron–field degrees of freedom. This system is integrated in terms of the elliptic Jacobian functions in the resonance limit. The solutions obtained describe the effects of trapping of an atom in the periodic potential of the standing light wave, and its cooling and heating, as well as the effect of the dynamic Rabi oscillations. The latter is caused by the interaction of the internal and external atomic degrees of freedom through the radiation field.     

The effect of atomic motion and two-quanta JCM on the information entropy

We study the interaction between a moving two-level atom and a single-mode field. The coupled atom-cavity system with atomic center-of-mass motion included is modeled by considering the dependence of the atomic motion along z-axis. At exact resonance between the internal atomic transition and the cavity eigenfrequency, an exact solution of the system is obtained and periodically modulated Rabi oscillations and regular translational motion are observed. We focused on the dynamics of both field Wehrl entropy and Wehrl phase distribution. The influence of the atomic motion on the evolution of von Neumann entropy and Wehrl entropy is examined. The results show that the atomic motion and the field-mode structure play important roles in the evolution of the von Neumann entropy, Wehrl entropy and Wehrl PD.     

Isotope separation via atom optics in the Bragg regime

We study the resonant interaction of a beam of mono-velocity two-level atoms with a standing-wave light field in the Bragg regime. The atomic beam consists of two different isotopes, and the density is sufficiently small so that at most one atom is inside the cavity at a time. The momentum transfer between the atoms and photons in the process significantly effects the center-of-mass motion of the atoms, thus separating the isotopes in different directions.     

Nonlinear coherent dynamics of an atom in an optical lattice

We consider a simple model of the lossless interaction between a two-level single atom and a standing-wave single-mode laser field which creates a one-dimensional optical lattice. The internal dynamics of the atom is governed by the laser field, which is treated as classical with a large number of photons. The center-of-mass classical atomic motion is governed by the optical potential and the internal atomic degrees of freedom. The resulting Hamilton-Schrö dinger equations of motion are a five-dimensional nonlinear dynamical system with two integrals of motion, and the total atomic energy and the Bloch vector length are conserved during the interaction. In our previous papers, the motion of the atom has been shown to be regular or chaotic (in the sense of exponential sensitivity to small variations of the initial conditions and/or the system’s control parameters) depending on the values of the control parameters, atom-field detuning, and recoil frequency. At the exact atom-field resonance, the exact solutions for both the external and internal atomic degrees of freedom can be derived. The center-of-mass motion does not depend in this case on the internal variables, whereas the Rabi oscillations of the atomic inversion is a frequency-modulated signal with the frequency defined by the atomic position in the optical lattice. We study analytically the correlations between the Rabi oscillations and the center-of-mass motion in two limiting cases of a regular motion out of the resonance: (1) far-detuned atoms and (2) rapidly moving atoms. This paper is concentrated on chaotic atomic motion that may be quantified strictly by positive values of the maximal Lyapunov exponent. It is shown that an atom, depending on the value of its total energy, can either oscillate chaotically in a well of the optical potential, or fly ballistically with weak chaotic oscillations of its momentum, or wander in the optical lattice, changing the direction of motion in a chaotic way. In the regime of chaotic wandering, the atomic motion is shown to have fractal properties. We find a useful tool to visualize complicated atomic motion-Poincaré mapping of atomic trajectories in an effective three-dimensional phase space onto planes of atomic internal variables and momentum. The Poincaré mappings are constructed using the translational invariance of the standing laser wave. We find common features with typical nonhyperbolic Hamiltonian systems-chains of resonant islands of different sizes imbedded in a stochastic sea, stochastic layers, bifurcations, and so on. The phenomenon of the atomic trajectories sticking to boundaries of regular islands, which should have a great influence on atomic transport in optical lattices, is found and demonstrated numerically.     

Atomic beam splitter from a mixture of atoms in the Bragg regime

We investigate the interaction of a standing-wave light field with the beam of two-level atoms moving in the Bragg regime. The atomic beam consists of two different isotopes and the density is sufficiently small so that at most one atom is inside the cavity at any time. The experimental setup is such that both the isotopes have the same momenta. The momentum transfer between the atoms and photons in the process essentially effects the center-of-mass motion of the atoms, thus separating the isotopes in different directions after specific interaction times.     

Interaction of nonlinear resonances in cavity QED

Strong coupling of the internal and external degrees of freedom of a cold atom to each other and to the spatially periodic field of the standing light wave in a high-finesse cavity is responsible for the dynamic instability of the atomic center-of-mass motion. Due to a weak interaction of the internal nonlinear resonances in the standard model of cavity QED, a stochastic layer appears, whose width in the semiclassical approximation is estimated in terms of the main parameters of the system: atomic recoil frequency, mean number of excitations, and detuning from the resonance. As a result, the atomic motion in the absolutely regular potential has the fractal character, with long Lévy flights alternating with small chaotic oscillations in potential wells.