Effect of Spontaneous Emission on Both Atomic Dynamics and Momentum Transfer of an Atomcavity System

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量子微腔中原子大质心动量转移问题

讨论了双模量子环形微腔中二能级原子与腔场相互作用的动力学问题,分析了量子微腔的双模腔场和原子质心交换动量的过程。通过控制双模光场的光子数,得到了原子质心运动可同时吸收或发射多个光子的结论,从而可以实现较大的原子质心动量转移过程,使原子分束效应更为显著。     

Momentum Transfer and Effect of Motion of Atomic Mass Centre on an Atom-Cavity System

For a special ∧-type atom with dark state, the problem of momentum transfer is discussed in detail. Effect of moving mass centre on atomic dynamics for various initial conditions is also studied. The numerical results show that the Doppler effect exercised by the motion of atomic mass centre can lead to the modified phenomenon of oscillation collapse and revival in the transition probability and the atomic population inversion.     

激光场线宽对四能级原子系统相干效应的影响

采用密度矩阵方程,在引入激光场线宽的条件下,计算了N型四能级原子系统中介质对探测场的吸收。结果表明:耦合场线宽的引入,消弱了四能级原子相干,对抑制吸收有增强作用,对增强吸收有抑制作用,即耦合场线宽的引入导致了退相干。控制场线宽的引入,在电磁感应透明中削弱了四能级原子相干性,降低了共振吸收,增强了光透明;在电磁感应吸收中,控制场线宽的增加使谱线中心两侧的吸收增强,削弱了谱线中心的吸收增强,从而使四能级系统的电磁感应吸收转换为电磁感应透明。     

Approximate Toffoli Gate Originated from a Single Resonant Interaction of Cavity Dissipation and Atomic Spontaneous Emission

We propose a potentially practical scheme to implement an approximate three-qubit Toffoli gate by a single resonant interaction in dissipative cavity QED in which the cavity mode decay and atomic spontaneous emission are considered. The scheme does not require two-qubit controlled-NOT gates but uses a three-qubit phase gate and two Hadamard gates, where the approximate phase gate can be implemented by only a single dissipative resonant interaction of atoms with the cavity mode. Discussions are made for the advantages and the experimental feasibility of our scheme.     

损耗腔中二能级原子的自发辐射谱

研究了耗散真空腔场中二能级单原子的辐射谱。推导出了原子辐射谱的一般表达式。讨论了腔的耗散系数以及在考虑腔耗散之后测量时间对辐射谱的影响。结果表明:当腔耗散系数增大时,峰的相对高度迅速减小,且数目减少;当腔耗散一定时,只有选择适当的测量时间,辐射谱才显现出比较明显的量子特性。     

Efficient Scheme for the Generation of Atomic Schrodinger Cat States in an Optical Cavity

An efficient scheme is proposed for the generation of atomic Schrodinger cat states in an optical cavity. Inthe scheme N three-level atoms are loaded in the optical cavity. Raman coupling of two ground states is achieved via alaser field and the cavity mode. The cavity mode is always in the vacuum state and the atoms have no probability ofbeing populated in the excited state. Thus, the scheme is insensitive to both the cavity decay and spontaneous emission.     

Fractional Angular Momentum of an Atom on a Noncommutative Plane

The mechanism of obtaining the fractional angular momentum by employing a trapped atom which possesses a permanent magnetic dipole moment in the background of two electric fields is reconsidered by using an alternative method. Then, we generalize this model to a noncommutative plane. We show that there are two different mechanisms,which include cooling down the atom to the negligibly small kinetic energy and modulating the density of electric charges to the critical value to get the fractional angular momentum theoretically.     

光子统计特性对原子能级AC Stark移动的影响

以相干态单模场和单模热光场引起的原子能级ACStark移动为例,分析了光子统计特性对能级移动规律的影响,能级AC Stark移动中包含了光场统计特性信息,这表明可以通过AC Stark效应研究场的统计性质。     

角动量和温度对耗散裂变明显触发的影响

对大量中重裂变系统(A>160)实验数据的分析表明:温度和角动量是触发裂变延迟效应的两个最基本条件.In的数据揭示了大角动量条件对轻系统情形的重要性.     

高动量分布对核反应中原子核的阻止本领的影响

利用同位旋相关的量子分子动力学模型研究了中能重离子碰撞过程中,具有不同中质比的中等质量核碰撞系统的高动量分布对原子核的阻止本领的影响,以及这种影响随入射能量的演化。研究结果表明:对于76Kr+76Kr,88Kr+88Kr碰撞系统,当入射能量较小时高动量分布对原子核的阻止本领影响很小;但当反应能量较大的时候,高动量分布对原子核的阻止本领影响较大,且这种影响随着入射能量和碰撞核质量的增大而增大。对于Ca同位素链的反应系统,高动量分布增大了反应系统的原子核的阻止本领。因此,高动量分布对中等质量核碰撞系统的原子核的阻止本领有重要影响,且与入射能量和碰撞核质量密切相关。Based on the isospin-dependent quantum molecular dynamics model, the effect of high momentum distribution on nuclear stopping in medium mass nuclear collision system is studied with different neutron-proton ratio in intermediate energy heavy ion collisions, and the evolution of this effect with the incident energy. The results show that when the incident energy is small, the high momentum distribution has little effect on the nuclear stopping. However, when the reaction energy is large, the high momentum distribution has a great influence on the nuclear stopping and the influence increases with the increase of incident energy and the mass of collision nucleus. For the Ca isotopes reaction system, high momentum distribution increases the nuclear stopping of the reaction system. Therefore, high momentum distribution has an important influence on nuclear stopping in medium mass nuclear collision system, and closely related to the incident energy and the mass of collision nucleus.     

Efficient Scheme for the Generation of Atomic Schrödinger Cat States in an Optical Cavity

An efficient scheme is proposed for the generation of atomic Schroedinger cat states in an optical cavity. In the scheme N three-level atoms are loaded in the optical cavity. Raman coupling of two ground states is achieved via a laser tield and the cavity mode. The cavity mode is always in the vacuum state and the atoms have no probability of being populated in the excited state. Thus, the scheme is insensitive to both the cavity decay and spontaneous emission.     

Control of Spontaneous Emission via a Single Elliptically Polarized Light in a Five-Level Atomic System

We investigate the features of the spontaneous emission spectra in a cold five-level atomic system coupled by a single elliptically polarized control field. We use wave function approach to derive the explicit and analytical expressions of atomic spontaneous emission spectra. It is shown that some interesting phenomena such as spectralline enhancement, spectral-line suppression, spectral-line narrowing, spectral-line splitting and dark fluorescence can be observed in the spectra by appropriately modulating the phase difference between the right-hand circularly (LHC) and left-hand circularly (RHC) polarized components of the elliptically polarized control field and the intensity of external magnetic field. The number of emission peaks, the positions of fluorescence-quenching points can be also controlled. Furthermore, we propose an ultracold 87Rb atomic system for experimental observation. These investigations may find applications in high-precision spectroscopy.     

含氧有机物对碱金属火焰原子发射光谱发射强度的影响规律

火焰原子发射光谱法(FAES)常用于分析检测碱金属各元素。实验结果表明,当试样中含有在水中溶解度较大的含氧有机物时,会对碱金属元素的火焰原子发射辐射强度产生影响。不同种类,不同浓度的含氧有机物使碱金属元素的发射强度改变的幅度是不同的,影响规律也有很大差异。有机物同分异构体以及官能团数量上的差异也对碱金属元素的发射强度产生影响,其影响规律也不相同。     

双频激光泵浦光纤放大器中的原子相干效应

用密度矩阵的方法从理论上分析了不同频率的两个激光场混合泵浦的光纤放大器中，由光场诱导的原子相干效应。并由此引入相干修正因子，通过修正的速率方程讨论了两光场与原子的相干作用对放大器增益的影响。     

The Effect of the Spin Angular Momentum on the Tight-Focusing Vortex Hollow Gaussian Beams

The propagation properties of a hollow Gaussian beam (HGB) carrying on-axis and off-axis vortices through a high numerical aperture lens are investigated. The intensity of the focused beam in the focal plane can be controlled by choosing the different topological charges, the beam order, and the semi-aperture angle. As intrinsic properties, vortex beams possess both spin and orbital angular momenta. The spin angular momenta (SAM) density can be treated as a vector in 3D since it exists in arbitrary orientation during the beam propagation. The vectors of SAM density orientation of the focused beam in 3D rotate around the central axis whose locations mainly rely on the vortices. The magnitude of the SAM density near the focus plane abruptly varies by altering the focal length of the lens. Under tightly focusing condition, two new pairs of vortices generate alternately on x and y axes in the vectorial electric fields, while the topological charges increase by one.     

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。     

角动量对断前粒子发射壳效应的影响

用Smoluchowski方程研究了角动量对一个轻的闭壳核¹³²Sn裂变前粒子蒸发壳效应的影响,发现壳对断前粒子发射的影响敏感地依赖于这个裂变系统的角动量.对可能的原因进行了讨论     

同位旋对断前粒子发射影响的角动量依赖性

对一个同量异位素链²⁰²Fr,²⁰²Po,²⁰²Tl和一个同位素链^189,202,212Po,用裂变扩散模型考察了角动量对裂变前粒子发射同位旋效应的影响.发现断前粒子发射的同位旋效应敏感地依赖于系统的自旋.高的角动量不但弱化了同位旋对粒子蒸发的影响,而且也降低了核耗散对粒子发射的影响.因此,为了更准确地用粒子多重性来提取核耗散系数,选择一个低自旋的复合系统是重要的