原子相干对里德伯原子稳定性的影响

研究了含级联双光子过程的多束缚态激光场诱导原子连续态结构系统中原子的相干捕获,给出了产生相干捕获的条件及暗态的表达式,讨论了原子初态和激光强度对原子相干捕获及粒子布居值在束缚态上分布的影响,揭示了原子相干对稳定里德伯原子的重要作用。     

~6Li超冷费米气体宽Feshbach共振散射的动力学演化研究

本文解析研究了~6Li超冷费米气体宽Feshbach共振散射动力学演化过程,将整个散射过程转化为一个单重态和一系列准连续态的散射共振,等效于涉及接触势的散射过程,在原子波包的持续时间内,束缚态中不断地出现原子布居,并将输入的波包非弹性散射到与之耦合的所有通道中。随着相互作用时间的增加,布居数转移幅度越来越大,连续态和束缚态之间的散射概率逐步增加,最终达到碰撞稳态。同时我们定量的计算了在原子散射过程中连续态和束缚态的动力学演化,在散射过程中连续态和束缚态的总概率守恒,连续态和束缚态之间布局数交换发生在散射共振前后的数十纳秒时间内。     

多能级原子系统暗压缩态的制备

基于二能级原子暗压缩态的制备方案，对多能级原子系统暗压缩态的产生机理进行研究，并提出一个如何在多能级原子系统中制备压缩态的方案。结果表明，在Lamb—Dicke近似下，考虑边带冷却效应就可以将多能级原子冷却至最低最子态；通过选择合适的入射光中心频率，利用多能级原子系统同样可以激光冷却被俘获的原子，并导致暗压缩态的出现。     

强激光场中原子的束缚态和连续态对高次谐波的影响

利用基函数展开结合线性最小二乘法方法求解含时薛定谔方程,研究了一维原子在强激光场中产生高次谐波过程中,束缚态和连续态以及它们的干涉效应对高次谐波的影响.结果表明,低能的高次谐波是由束缚态束缚态之间的相互作用产生的,高能的高次谐波是由束缚态连续态之间的相互作用产生的,而截断频率后消失的高次谐波是由于束缚态束缚态与束缚态连续态之间存在干涉效应的结果 关键词： 线性最小二乘法 强激光场 高次谐波的产生     

分子多光子共振吸收的理论研究

首先利用Floquet理论得到共振态的本征函数,再通过求解束缚态与连续态的耦合矩阵而得到束缚态的解离几率,最后得到任一束缚态通过耦合而解离的解离几率及衰变宽度等,利用我们得到的公式,对不转动的双原子分子及双原子分子模型进行了计算,在外场不是特别强的情况下,得到了一些很好的结果。     

激光对双原子分子自发辐射的影响

在偶极近似下，研究了激光场中双原子分子的修饰态（ｄｒｅｓｓｅｄ ｓｔａｔｅ），讨论了修饰态之间的自发辐射；与没有激光时相应过程比较，结果表明激光影响下荧光呈多重结构。     

Λ型原子-分子三能级系统的分子转化率问题

利用解析和数值的方法对Λ型原子-分子三能级系统的量子动力学行为进行了详细研究，同时对该系统中分子转化率进行了研究.结果发现，不同的系统初态对转化率有比较大的影响，理想情况下，在初始态为原子态且在两个拉比频率相等时，可以得到较高的分子转化率，而光场的失谐会造成转化率的降低；初始态为暗态时，分子转化率为一常数，光场的失谐会增大转化率.     

氦原子1snd(n=4—11)组态下1D—3D谱项分裂值的计算

利用多体微扰理论(MBPT)计算了氦原子1snd(n=4—11)组态的１Ｄ—^３Ｄ谱项分裂值.基于两种不同的模型分别计算Rayleigh-Shrdinger微扰展开式中仅含束缚态的部分和包含连续态的部分.对于束缚态，较严格地通过自洽迭代求解Hartree方程构造零级近似波函数，并利用积分处理方法对无穷项求和中的余项给出了近似算法.而对于连续态波函数，则采用简化的氢原子势模型.按照Rayleigh-Shrdinger微扰展开方法，将Rydberg态的微扰论修正计算至三级.计算表明，二级和三级微扰对谱项分裂的贡献主要来自于束缚态求和部分.单态-三重态精细结构分裂的计算结果与两组实验结果基本符合. 关键词： 氦原子 Rydberg态 多体微扰 组态波函数 能级分裂     

圆柱方势阱的解在人造原子理论中的应用

使用圆柱方势阱计算了含有一个电子的类圆柱形人造原子的电子态结构．计算结果表明，在一定条件下，这个人造原子存在束缚态．     

类锂离子(Z=11～20)32D-n2F偶极跃迁的振子强度

利用全实加关联方法得到的波函数计算类锂离子(Z=11～20)1s23d-1s2nf(4≤n≤9)的偶极跃迁振子强度,三种规范下的计算结果符合的很好.将分立态的振子强度结果与单通道量子亏损理论相结合,计算在电离阈附近(|E|≤I/2)分立态间的束缚态-束缚态跃迁振子强度与束缚态-连续态跃迁的振子强度密度,实现了具有较大核电荷数的类锂离子量子跃迁特性的全能域理论预言.     

Dynamical instability and adiabatic evolution of the atom--homonuclear--trimer dark state in a condensate system

This paper investigates the dynamical instability and adiabatic evolution of the atom--homonuclear--trimer dark state of a condensate system in a stimulated Raman adiabatic passage aided by Feshbach resonance. It obtains analytically the regions for the appearance of dynamical instability caused by the interparticle interactions. Moreover, the adiabatic property of the dark state is also studied in terms of a newly defined adiabatic fidelity. It shows that the nonlinear collisions have a negative effect on the adiabaticity of the dark state and hence reduce the conversion efficiency.     

Optimum quantum state of light for gravitational-wave interferometry

The laser interferometric gravitational-wave detectors are sensitive to the quantum state of light employed in the dark port of interferometric system. In this paper a general quantum state for the dark input port is assumed. The quantum state of light is expanded versus the Fock states. The quantum noise of interferometric system is computed as a function of the quantum state of light. The variational method and the genetic algorithm are employed to determine the coefficients of the dark input port and the laser input power for the minimization of the quantum noise. Calculation shows that the optimum quantum state for the dark input port is very close to the vacuum squeezed state. For this optimum quantum state the quantum noise and optimum laser power reduces one order of magnitude relative to the conventional interferometer.     

Test by NMR of the phase coherence of electromagnetically induced transparency

Electromagnetically induced transparency is an effect observed in atomic systems, originating from quantum interference, in which electromagnetic transitions to and from a certain quantum state become suppressed. This dark state is also characterized by a quantum phase, relative to other states, which theoretically should stop evolving, but remain phase coherent, during transparency. We test this theoretical prediction using techniques developed for liquid-state nuclear magnetic resonance quantum computation, applied to a spin-7/2 nuclear spin system. A sequence of quantum operations is applied to create the dark state, and during transparency its phase evolution is measured relative to a reference state using Ramsey interferometry. Experimental measurements of the fringe visibility are in excellent agreement with theoretical expectations, taking into account measured decoherence rates.     

Six-Fold Degenerate Dark States in a Four-Level Atomic System

With all driving fields on Raman resonance, a tripod-type atomic system quickly evolves into a dark state decoupled from the lossy excited level. The dark state depends strongly on field Rabi frequencies, spontaneous decay rates, and the initial atomic population in a complicated way. Analytical results reveal that it is a sixfold degenerate dark state with its three components superposed both coherently and incoherently due to population redistribution from spontaneous emission.     

Holographic dark energy model and scalar-tensor theories

We study the holographic dark energy model in a generalized scalar tensor theory. In a universe filled with cold dark matter and dark energy, the effect of potential of the scalar field is investigated in the equation of state parameter. We show that for a various types of potentials, the equation of state parameter is negative and transition from deceleration to acceleration expansion of the universe is possible.     

Influence of self-phase modulation on coherent effects in five-level system

The possibility of formation of a coherent dark state in the five-level system in the entire volume of the medium in an adiabatic pulse propagation is investigated. It is shown that the dark state formation is independent on the value of the first two-photon detuning from the resonance, which may be changed during the propagation in the medium. In the case of the M-type system with the equal strengths of oscillators at the extreme transitions it is shown that the self-phase modulation does not influence the coherent effects while in the ladder-type system it may lead to the destruction of the dark state. The estimation of the length of the medium in which the propagation effects are negligible is obtained.     

实现暗态的三芯耦合波导设计及其非线性脉冲传输特征

暗态效应被广泛应用于量子信息处理.通过纤芯结构的设计,在三芯耦合波导中实现了该量子效应,并数值研究了非线性对暗态的影响.研究发现,在几个耦合长度内,当波导1中的输入为归一化功率等于1的低能量光脉冲时,波导2与3中没有光传输;当入射光的归一化功率增大到1000时,波导2与3中依然没有明显光传输,且对比度超过4个数量级.然...     

Coherent control of a light field with electromagnetically induced transparency in a dark state Raman coherent tripod system

A dark state superposition is employed and formed a tripod-like system. A weak probe pulse propagates in it can experience a crossover from absorption to transparent and then to amplification, and its group velocity can be controlled in any desired speed by determining the initial states of the dark state superposition.     

Atom-molecule dark state: the exact quantum solution

Developments in ultracold atomic physics have enabled the generation of an atom-molecule dark state in dilute quantum gases. Previous studies of this dark state were all carried out in the mean-field regime. Here we present an exact quantum many-body wave function for the atom-molecule dark state for an ideal system (in the absence of losses and two-body collisions). Using this exact quantum wave function, we are able to validate the mean-field solution to be a good approximation when the particle number N is large. For small N, unique quantum features will become important.     

Spherical Collapse with Dark Energy

I discuss the work of Maor and Lahav (JCAP 0507:003, 2005), in which the inclusion of dark energy into the spherical collapse formalism is reviewed. Adopting a phenomenological approach, I consider the consequences of (a) allowing the dark energy to cluster, and, (b) including the dark energy in the virialization process. Both of these issues affect the final state of the system in a fundamental way. The results suggest a potentially differentiating signature between a true cosmological constant and a dynamic form of dark energy. This signature is unique in the sense that it does not depend on a measurement of the value of the equation of state of dark energy.