利用腔QED技术控制传输任意两原子态

我们提出一个利用腔QED技术控制传输任意两原子态的方案.在此方案中,我们选择一个GHZ态和一个EPR对作为量子通道.在控制者的帮助下,发送者可以把量子信息传送给接收者.在传输过程中,两对原子分别与两个全同单模场相互作用,同时两对原子分别由两个全同经典场驱动.该方案对腔衰变和热场不敏感,并且传输成功的几率为1.     

二阶离化对缀饰态稳定性的影响

推广了包含二阶离化和自电离耦合的缀饰态理论,并研究了二阶离化对缀饰态稳定性的影响。结果表明:二阶离化破坏了缀饰态的稳定性,但二阶离化中的C-C耦合在某种程度上可以降低这种不稳定性。 关键词：     

双模相干态和压缩真空态光场-非等同两原子体系的腔场谱

研究了两个非等同二能级原子与双模腔场相互作用过程的腔场谱.导出了双模初始光场处于任意量子态时腔场谱的计算公式,给出了光场处于相干态和压缩真空态时的数值结果,讨论了相对耦合常数R=g2/g1和初始场强对腔场谱的影响.发现相干态光场的腔场谱在R很小时为双峰,在R接近于1时为3峰.压缩真空态的腔场谱在弱场条件下表现为复杂的多峰结构,在强场条件下则只有单一经典共振峰或裂距很小的双峰.     

缀饰态理论在碰撞能量转移过程中的应用

利用缀饰态理论研究了由分子和原子组成的混合共振系统中分子和原子之间的碰撞能量转移过程.结果发现:在单模强激光场作用下,该混合共振系统由于发生了碰撞能量转移,而使得粒子在相应能级上产生重新布居,并在一定条件下呈现出量子干涉增强效应,导致了不同缀饰态能级之间出现交叠区.这一结果与现有实验报导相符,为研究多能级系统的量子干涉效应提供了一种新的理论途径.     

"两原子-双模腔场"系统的腔场谱

研究了存在偶极相互作用的两等同原子与双模腔场共振相互作用双光子过程的腔场谱,研究发现,当两模初态都为光子数态或相干态时,两模腔场谱之间有很强的相互影响,在两模场强相同时,两划的光谱结构也相同,且在强场下呈现三峰结构;当两模初态场强不同时,较强的一模出现简单的单峰结构,而较弱模光谱中三峰的距离随另一模光子数的增加而增大。当两模均为压缩真空态时,在强场下得到经典共振荧光谱,且两模腔场谱之间的相互影响很弱。     

K_2分子在强激光场下的量子调控:缀饰态选择性分布

利用含时量子波包法理论研究了分子在强激光场条件下的量子调控.选取K2分子的三态模型(基态|X〉、激发态|B〉和电离态|X+〉)作为研究对象.在强激光场的作用下,激发态|B〉缀饰成两个子态:|α〉态和|β〉态.分析K2分子电离后的光电子能谱,可以得到缀饰态|α〉和|β〉的能量和概率分布信息.同时,根据分子的缀饰态理论,提出了K2分子的缀饰态选择性分布方案.研究表明:调节激光场的强度可以实现对缀饰态能量的调控,改变激光场的波长可以实现对缀饰态概率的选择性分布.     

控制Tavis-Cummings模型中两原子X态的纠缠突然死亡与突然产生

研究了初态为X态时Tavis-Cummings模型中具有偶极相互作用两原子的纠缠演化特性,在演化过程中,同时号码出现了两原子的纠缠突然死亡(ESD)与突然产生(ESB)两种有趣的现象.详细分析了两原子初始态的纯度、偶极相互作用、光场粒子数对这两种现象出现时间的影响,进一步给出了初始为混态时ESB与ESD的转换条件.计算结果表明,上述系统参量对两原子的纠缠演化、ESB与ESD有重要的影响,偶极相互作用会改变纠缠度的振荡周期,使出现ESD的时间间隔减少;随着初始两原子纠缠纯度的增大,纠缠突然产生以及纠缠突然死亡存在的时间缩短,并且可以提高两原子之间的纠缠;对于特殊的初态,产生了纠缠不变性以及固定的两原子纠缠,该定值受两原子初始状态的纯度控制。     

基于两原子同时和腔场共振作用制备两原子纠缠态的腔QED方案(英文)

我们提出了一个将两个远离的原子制备成纠缠态的腔QED方案,该方案基于两个原子同时和一个腔场发生共振作用.在这个方案里,我们利用一个事先制备好的纠缠态将另外两个分离的原子制备成纠缠态.该方案仅包含两个原子和腔场的共振相互作用,不需要用腔场存储量子信息,并且原子和腔场作用时间极短.因此,我们的方案基于目前的腔QED技术是可以实现的.     

B介子非轻子衰变中的微扰QCD方法

在因子化方法的基础上，发展和应用了微扰QCD的方法来计算B介子的非轻子衰变. 通过应用Sudakov形状因子的压低效应和介子的光锥波函数，可以计算B介子衰变的因子化图的贡献以及非因子化和湮没图的贡献. 许多衰变道的分支比与实验非常符合. 作者也作出了它们的CP破坏大小的预言，有待于实验的检验.     

Time Evolution of Vibration-Induced Excited State Decay

A simple model consisting of two electronic levels and one vibrational mode (phonon) was theoretically studied. The electronic-vibrational interaction was linear in the vibrational displacement. The vibrational mode was taken in the harmonic approximation and was attached to the thermal bath formed by the ambient environment. The kinetic constants of the vibrational dissipation were of the second order in the vibrational-bath coupling and were taken in the Markovian limit. Although, depending on the parameters of the model, different curves of the non-radiative vibration-induced excited state decay were obtained, in general, three time intervals, corresponding to different physical behaviour, were found. In the short-time interval, small oscillations superimposed on the excited state decay were observed. They were determined by the vibrational frequency and influenced by electronic-vibrational coupling. In the middle-time interval, almost quasi-exponential decay was detected; its rate constant increased with stronger electronic-vibrational interaction and speed of vibrational relaxation. In the long-time interval, the decay was very slow and, under special conditions, even an asymptotic non-zero excited state population was observed. Its value increased with the strength of the off-diagonal electron-vibrational coupling. Links of the parameters of the model with quantum chemical terms were estimated.     

夸克偶素双光子衰变的相对论效应

考虑到各种相对论效应，唯象地研究了0－＋和0＋＋夸克偶素的双光子衰变. 相比于通常用的非相对论近似，我们的相对论唯象方法给出了3种分别由介子内夸克相对动量，相对能量，以及它的自旋形式的选取带来的效应. 在cc和ss中我们做了具体的分析     

Role of Mode-mode Coupling in Short-time Excited State Decay

Master equation of a relevant electronic and vibrational system is derived for a special diabatic basis corresponding to vertical processes. It is shown that bath modes contribute dynamically to the inter-state coupling only at short times. For long times the bath-induced inter-state coupling is static and increases with the contribution of bath modes to the Stokes shift and to the Herzberg-Teller correction of the excited state. Simultaneously, the time evolution of excited state population is studied numerically for the system consisting of two electronic levels interacting with two vibrational modes, coupled to a heat bath. A mutual coupling of the vibrational modes in the excited state is taken into account (Duschinsky effect). Excited state population relaxes faster if interacting vibrational mode dissipates its energy via vibrational mode of a smaller eigenfrequency. Fast component of excited state depopulation cannot be achieved via coherent mode-mode coupling, if the second mode is not directly coupled to the electronic inter-state transition.     

三原子体系的合作共振荧光

本文用缀饰原子本征态的方法,导出三原子体系合作共振荧光过程的主方程。求出了共振荧光的谱线结构,各谱线的权重比及各谱线的弛豫速率。文中报道了三原子共振荧光由七条谱线组成,每条谱线又有自己的精细结构。作者认为各谱线的分裂原因在于缀饰原子偶极矩之间的相互耦合。     

Probabilistic Teleportation of an Arbitrary Two-Atom State in Cavity QED

We propose a scheme for the teleportation of an arbitrary two-atom state by using two pairs of two-atom nonmaximally entangled states as the quantum channel in cavity QED. It is Shown that no matter whether the arbitrary two-atom pure state to be teleported is entangled or not, our teleportation scheme can always be probabilistically realized. The success prohability of teleportation is determined by the smaller coemcients of the two initially entangled atom pairs.     

Generation of Two-Atom Cluster State via Cavity QED

We propose a physical scheme for generating a two-atom cluster state through the simultaneous interaction of two two-level atoms with a single-mode cavity field prepared initially in an odd-coherent state under a large-detuned limit. The influence of the dissipation constant, the intensity of the field and the imperfect manipulation on the preparation scheme are investigated. It is shown that when the intensity of the cavity is large enough, the influence of the cavity decay is ettlciently suppressed. The possible error in the implementation of the cluster state is negligible when the time difference between two atoms crossing the cavity axis is small. It is suggested that the scheme can be realized by current technologies.     

Teleportation of an Arbitrary Two-Atom Entangled State via Thermal Cavity

We present an experimentally feasible scheme for teleportation of an arbitrary unknown two-atom entangled state by using two-atom Bell states in driven thermal cavities. In this scheme, the effects of thermal field and cavity decay can be all eliminated. Moreover, the present scheme is feasible according to current technologies.     

Alternative Scheme for Teleportation of Two-Atom Entangled State in Cavity QED

We have proposed an alternative scheme for teleportation of two-atom entangled state in cavity QED. It is based on the degenerate Raman interaction of a single-mode cavity field with a ∧-type three-level atom. The prominent feature of the scheme is that only one cavity is required, which is prior to the previous one. Moreover, the atoms need to be detected are reduced compared with the previous scheme. The experimental feasibility of the scheme is discussed.The scheme can easily be generalized for teleportation of N-atom GHZ entangled states. The number of the atoms needed to be detected does not increase as the number of the atoms in GHZ state increases.     

Alternative Scheme for Teleportation of Two-Atom Entangled State in Cavity QED

We have proposed an alternative scheme for teleportation of two-atom entangled state in cavity QED. It is based on the degenerate Raman interaction of a single-mode cavity field with a A-type three-level atom. The prominent feature of the scheme is that only one cavity is required, which is prior to the previous one. Moreover, the atoms need to be detected are reduced compared with the previous scheme. The experimental feasibility of the scheme is discussed. The scheme can easily be generalized for teleportation of N-atom GHZ entangled states. The number of the atoms needed to be detected does not increase as the number of the atoms in GHZ state increases.