两原子与双膜腔场的多光子喇曼相互作用

研究了两个等同有效二能组原子与双模腔场的多光子喇曼相互作用．导出了双模腔场处于任意态时，该系统中两原子辐射谱的一般表达式，并分析了辐射谱的特点.     

两等同双能级原子与三模腔场任意多光子共振相互作用辐射谱的一般特征

本文研究了两个偶极——偶极力关联的等同双能级原子与三模腔场间任意多光子共振相互作用的辐射谱。对三模腔场分别处于不同数态：即三模均为真空场、三模均为强场、一模为真空场两模为强场以及两模为真空场一模为强场时辐射谱的结构特征及物理特性进行了详细分析．从而揭示出“三模腔场——两原子系统”的多光子辐射谱的一般特征．     

双模热辐射腔场激励下A型三能级原子的辐射谱

采用时间演化算符方法,研究A型三能级原子与双模热辐射腔场共振相互作用的辐射谱．给出了辐射谱一般公式．并讨论在双模热辐射光场激励下的辐射频谱结构．结果表明：无论下能级简并与否,双模热辐射光场平均光子数很小时均出现拉比（Rabi）分裂;辐射谱一般呈对称的十峰结构。     

简并量子拍频三能级单原子的辐射谱

采用时间演化算符方法,研究腔内单模光场中被相干微波场驱动的Λ型简并量子拍频三能级单原子的辐射谱,给出了辐射光谱公式．在初始光场为粒子数态光场激励下,辐射谱一般为对称的六峰结构,各峰值频率与作用光场的光子数有关,而强度与驱动微波场相关;并讨论光谱结构与耦合常数之间的关系     

二能级原子与双模腔场的喇曼相互作用

研究了单个二能级原子与双模辐射腔场的喇曼相互作用，计算了原子的辐射谱，讨论了双模腔场处于不同数态时辐射谱的新特点     

双模热辐射腔场激励下Λ型三能级原子的辐射谱

采用时间演化算符方法,研究Λ型三能级原子与双模热辐射腔场共振相互作用的辐射谱.给出了辐射谱一般公式.并讨论在双模热辐射光场激励下的辐射频谱结构.结果表明:无论下能级简并与否,双模热辐射光场平均光子数很小时均出现拉比(Rabi)分裂;辐射谱一般呈对称的十峰结构.     

一个基于腔衰减的四原子纠缠态制备方案

基于A型三能级原子与腔场及经典场的相互作用理论,利用单光子探测器对从光腔中泄漏出来的光子进行符合测量,提出了一个四原子纠缠态的制备方案,四个分别处于不同光腔中的原子将以一定的概率处于GHZ态。     

耗散腔场中两原子间的纠缠特性

研究了在大失谐条件下一位于能量耗散腔中,两个二能级原子与单模辐射场相互作用系统中原子间纠缠的时间演化特性,讨论了两原子的初始状态、腔场衰变常数以及光场的平均光子数对原子纠缠度的影响．结果表明：当两原子均处于激发态或基态时,两原子始终处于分离状态;而当两原子初始均处于激发态与基态的相干叠加态时,腔场损耗对原子纠缠度的影响随时间的演化逐渐消失,但原子偶极一偶极相互作用使原子间的纠缠程度得到加强．     

Bell态原子与大失谐腔相互作用的辐射谱

用时问演化算符的方法,研究了两个全同的二能级Bell态原子与腔场大失谐作用时的辐射谱.消相干Bell态原子不产生辐射,其他三个Bell态原子辐射谱频谱结构相同,并且在Fock态光场作用下,辐射谱都呈现单峰结构,而在相干光场和热光场作用下,辐射谱呈现出强度分布不同的多峰结构.     

非等同两原子-双模热光场系统的腔场谱

为获得两个非等同二能级原子与双模光场相互作用过程的腔场谱特性,通过求解本征方程导出了双模初始光场处于任意强度的热光场时腔场谱的计算公式,给出了数值计算结果．文中还讨论了相对耦合常数和初始场强对腔场谱的影响,发现在相对耦合常数为零且初始场较弱的条件下,两模腔场谱均为双峰结构;随着相对耦合常数的增大,双峰逐渐靠近,到相对耦合常数为1时,每模腔场谱都合并为单峰．随着一模光场平均光子数的增大,本模腔场谱双峰之间的距离减小,而另一模腔场谱双峰之间的距离增大。     

奇偶纠缠相干态光场驱动下Λ-型三能级原子的辐射谱

采用时间演化算符方法,研究Λ-型三能级原子与奇偶纠缠相干态光场共振相互作用的辐射谱.给出了辐射谱一般公式.结果表明:不论下能级简并与否,奇偶纠缠相干态光场平均光子数很小时均出现拉比分裂,且下能级简并时,强度随奇偶纠缠相干态光场纠缠程度的增加而增加;两下能级非简并时,一模场驱动的辐射谱峰高随纠缠程度的增加而增加,而另一模场驱动的辐射谱峰高随纠缠程度的增加而减小.一般辐射谱呈对称的10蜂结构.     

驱动单个原子制备纠缠相干态

提出一种利用经典场驱动单个原子与一个多模腔场相互作用制备腔场的多模纠缠相干态的方案.交替调整原子的跃迁频率,使原子与经典场及多模腔场交替作用,通过对原子的选态测量使多模腔场塌缩为多模纠缠相干态.     

Cavity cooling of a single atom

All conventional methods to laser-cool atoms rely on repeated cycles of optical pumping and spontaneous emission of a photon by the atom. Spontaneous emission in a random direction provides the dissipative mechanism required to remove entropy from the atom. However, alternative cooling methods have been proposed for a single atom strongly coupled to a high-finesse cavity; the role of spontaneous emission is replaced by the escape of a photon from the cavity. Application of such cooling schemes would improve the performance of atom-cavity systems for quantum information processing. Furthermore, as cavity cooling does not rely on spontaneous emission, it can be applied to systems that cannot be laser-cooled by conventional methods; these include molecules (which do not have a closed transition) and collective excitations of Bose condensates, which are destroyed by randomly directed recoil kicks. Here we demonstrate cavity cooling of single rubidium atoms stored in an intracavity dipole trap. The cooling mechanism results in extended storage times and improved localization of atoms. We estimate that the observed cooling rate is at least five times larger than that produced by free-space cooling methods, for comparable excitation of the atom.     

Light interference from single atoms and their mirror images

A single atom emitting single photons is a fundamental source of light. But the characteristics of this light depend strongly on the environment of the atom. For example, if an atom is placed between two mirrors, both the total rate and the spectral composition of the spontaneous emission can be modified. Such effects have been observed using various systems: molecules deposited on mirrors, dye molecules in an optical cavity, an atom beam traversing a two-mirror optical resonator, single atoms traversing a microwave cavity and a single trapped electron. A related and equally fundamental phenomenon is the optical interaction between two atoms of the same kind when their separation is comparable to their emission wavelength. In this situation, light emitted by one atom may be reabsorbed by the other, leading to cooperative processes in the emission. Here we observe these phenomena with high visibility by using one or two single atom(s), a collimating lens and a mirror, and by recording the individual photons scattered by the atom(s). Our experiments highlight the intimate connection between one-atom and two-atom effects, and allow their continuous observation using the same apparatus.     

基于原子与光场共振相互作用的W态融合

基于腔量子动力学(QED)系统,从N个原子和M个原子的W态中各取1个原子同时送入真空腔场,利用原子与腔场相互作用实现2个W态融合.当原子与腔场发生共振作用后,探测腔场.结果表明:若有1个光子,则初始的2个W态以一定概率融合为(N+M)个原子W态;若腔场中没有光子,则探测飞出2个原子,若2个原子中有1个原子处于激发态,则初始的2个W态以一定概率融合为(N+M-2)个原子W态;若2个原子均处于基态,则余下的(N-1)个原子W态和(M-1)个原子W态仍可按此方案循环融合.     

纠缠态原子与双模压缩态光场相互作用中的纠缠特性

对于处于纠缠态的2个原子与双模压缩光场的相互作用,研究了原子与光场之间以及双模光场中2模之间的纠缠性质.令2个原子中的一个留在腔外,另一个进入腔中与光场发生相互作用,发现一般情况下纠缠度随时间周期性地变化,并且周期不受腔外原子的旋转角度以及纠缠态中相位差的影响;但当光场态中的压缩参量与腔外原子的旋转角度满足一定关系时,原子与光场会一直处于解纠缠状态.     

四能级原子受激辐射的非经典特性

本文研究初始处于最高激发态的级联型四能级原子,同初始处于相干态的单膜腔场的相互作用,通过求解薛定谔方程而求得该原子——场声统的密度算符,进而研究原子受激辐射的非经典特性。指出这里存在着较深的压缩和长时间的反聚束与聚束效应间的振荡.     

量子阱微腔激光器中TE和TM模自发发射的差异

利用金属镜面微腔激光器中真空场和量子阱中电子态函数,对比了ＴＥ模和ＴＭ模的自发发射谱,发现腔长为半个波长的微腔激光器可以增进ＴＥ模垂直方向的自发发射,同时ＴＭ模却得到很大抑制,并且它们总的自发发射也存在差异。     

Trapping an atom with single photons

The creation of a photon-atom bound state was first envisaged for the case of an atom in a long-lived excited state inside a high-quality microwave cavity. In practice, however, light forces in the microwave domain are insufficient to support an atom against gravity. Although optical photons can provide forces of the required magnitude, atomic decay rates and cavity losses are larger too, and so the atom-cavity system must be continually excited by an external laser. Such an approach also permits continuous observation of the atom's position, by monitoring the light transmitted through the cavity. The dual role of photons in this system distinguishes it from other single-atom experiments such as those using magneto-optical traps, ion traps or a far-off-resonance optical trap. Here we report high-finesse optical cavity experiments in which the change in transmission induced by a single slow atom approaching the cavity triggers an external feedback switch which traps the atom in a light field containing about one photon on average. The oscillatory motion of the trapped atom induces oscillations in the transmitted light intensity; we attribute periodic structure in intensity-correlation-function data to 'long-distance' flights of the atom between different anti-nodes of the standing-wave in the cavity. The system should facilitate investigations of the dynamics of single quantum objects and may find future applications in quantum information processing.