三体相互作用下三势阱中玻色-爱因斯坦凝聚体的稳定性研究

着重研究受到非弹性碰撞相互作用,即考虑有三体复合耗散和原子填充时三势阱中玻色-爱因斯坦凝聚体的动力学性质.运用三模近似,得到三个耦合的GP方程,用数值的方法得到不同散射长度的数值结果,展示了玻色-爱因斯坦凝聚体在零相位和π相位时,会出现自俘获及量子隧穿现象,且定态解的稳定性与相位有关.     

玻色-爱因斯坦凝聚体干涉效应的数值研究

本文采用辛算法数值求解了GrossPitaevskii (GP) 方程,研究了玻色爱因斯坦凝聚体的干涉现象.讨论了两个凝聚体间以及三个凝聚体间的干涉效应并对两者做了比较,其差异之处我们认为是由增大的凝聚体间的相互作用造成的.     

三势阱中玻色-爱因斯坦凝聚体的三模量子纠缠

在对称三势阱中，通过绝热地调节势阱间两个相邻势垒的高度，使得相邻的玻色-爱因斯坦凝聚体发生交叉弹性碰撞，选择适当的相互作用时间，我们提出了一种制备三体玻色-爱因斯坦凝聚场模量子纠缠的理论方案。接着，基于两体concurrence的计算方法，我们获得了该三体场模纠缠态的剩余纠缠度。[编者按]     

玻色-爱因斯坦凝聚体干涉现象的数值模拟

采用含时非线性薛定谔方程的数值解法模拟了两种情况下玻色-爱因斯坦凝聚体的演化.一种是在初始状态中有两个包含粒子数差别很大、在空间上可区分的玻色-爱因斯坦凝聚体的情况;另一种是一个玻色-爱因斯坦凝聚体被外力一分为二后在自由空间及约束势阱中继续演化的情况. 关键词：     

玻色-爱因斯坦凝聚体在光势阱中的量子隧穿

微观粒子因具有波动性而能以一定的概率穿过比它动能更高的势垒，这一现象称为隧道效应，玻色-爱因斯坦凝聚体在不同的囚禁势阱中表现出不同的隧穿特性，文章作者用周期瞬子方法首次研究了光势阱中玻色-爱因斯坦凝聚体的量子隧穿，研究表明，处在光势阱中的玻色-爱因斯坦凝聚体不仅表现出Landau-Zenner隧穿，而且出现新的Wannier-Stark隧穿，Wannier-Stark隧穿系数大约是Landu-Zener隧穿系数的1000倍，并得到了隧穿率随温度的变化规律，包括经典热激活、热助隧穿和量子隧穿，理论的计算结果与Yale大学和意大利INFM研究组关于Landau-Zener隧穿的实验结果相符合，同时给出了如何在实验上发现Wannier-Stark隧穿的参数区间。     

玻色-爱因斯坦凝聚体Rosen-Zener跃迁中的多体量子涨落效应

研究了处于对称双势阱中玻色一爱因斯坦凝聚体Rosen—Zener跃迁过程的多体量子涨落效应,分析了末态平均布居数差与扫描周期的关系．线性情况下,得到了末态平均布居数差关于扫描周期的解析表达式,该结果与平均场下的结果完全一致,并利用数值方法进行了验证．非线性情况下,通过数值计算发现,快速扫描时末态平均布居数差与平均场情况下的结果符合比较好;然而绝热扫描时与平均场情况却有着很大的不同：末态平均布居数差随扫描周期的变化不再是平均场情况下的方波形式而是类似于正弦型的振荡,而且振荡周期会随着粒子数Ⅳ以及非线性参数c的增加而增大．     

两个玻色-爱因斯坦凝聚体间相互作用的数值研究

本文采用辛算法数值求解一维含时Gross-Pitaevskii(GP)方程.研究了存在陷俘势和撤掉陷俘势时两个凝聚体间的相互作用.发现当存在陷俘势时两个凝聚体间发生弹性碰撞;在零时刻撤掉陷俘势时两个凝聚体间发生干涉现象;当t=2时撤掉陷俘势两个凝聚体间发生了复杂现象.     

玻色爱因斯坦凝聚体中杂质的相互作用

文章研究了两个杂质浸入玻色凝聚体中的相互作用.通过使用微扰法,计算了在弱杂质-玻色子相互作用区域中的基态能量.结果表明基态能量与两杂质之间的相对距离有关.从基态能量出发,研究发现不管杂质与玻色子相互作用是处在排斥状态还是吸引状态,两杂质之间都有保持吸引趋势;而当一个杂质与玻色子相互作用是吸引时,另一个为排斥时,两个杂质之间呈现出了排斥的效果.通过杂质之间有效力的计算也验证了上述现象,进一步研究凝聚体密度背后的力学机制,再次得出了一致结论.     

非谐势阱中玻色-爱因斯坦凝聚的数值计算

从G-P平均势场理论出发,探讨了玻色-爱因斯坦凝聚(BEC)的G-P方程的一维形式,用数值计算方法研究了非谐势阱中非理想玻色凝聚气体的基态和第一激发态解.给出了能量随非线性系数的变化规律.     

玻色-爱因斯坦凝聚物理本质探索

针对玻色-爱因斯坦凝聚这一课题,综述了玻色-爱因斯坦凝聚理论的诞生和发展、概念,着重阐述了其形成条件、物理机制、性质及其应用,接着将介绍一些玻色—爱因斯坦凝聚的实验和国内外的研究动态,最后展望了其发展前景。     

Harmonic Interaction Model and Its Applications in Bose–Einstein Condensation

We exactly solve the model of N harmonic interacting Bosons in a harmonic trap in any dimension. The exact ground state wavefunction, free energy, spectrum, and low excitation states are calculated. The finite particle number effect is addressed when the exact solution is compared with a mean field solution. Then we compare the harmonic interaction system with a pseudo-potential interaction system. In spite of the seemingly quite different nature of interaction, several similarities are found between the two systems.     

Bose–Einstein Condensation for Homogeneous Interacting Systems with a One-Particle Spectral Gap

We prove rigorously the occurrence of zero-mode Bose–Einstein condensation for a class of continuous homogeneous systems of boson particles with superstable interactions. This is the first example of a translation invariant continuous Bose-system, where the existence of the Bose–Einstein condensation is proved rigorously for the case of non-trivial two-body particle interactions, provided there is a large enough one-particle excitations spectral gap. The idea of proof consists of comparing the system with specially tuned soluble models.     

Bose–Einstein condensation of lithium

7 Li has been studied in a magnetically trapped gas. Many-body quantum theory predicts that the occupation number of the condensate is limited to about 1400 atoms because of the effectively attractive interactions between ⁷Li atoms. Using a versitile phase-contrast imaging technique, we experimentally observe the condensate number to be consistent with this limit. We discuss our measurements, the current theoretical understanding of BEC in a gas with attractive interactions, and future experiments we hope to perform. Received: 4 June 1997     

The dynamics of three coupled dipolar Bose Einstein condensates

The dynamics of the three coupled dipolar Bose–Einstein condensates containing N bosons is investigated within a mean-field semiclassical picture based on the coherent-state method. Varieties of periodic solutions （configured as vortex, single depleted well, and dimerlike states） are obtained analytically when the fixed points are identified on the N=constant. The system dynamics are studied via numeric integration of trimer motion equations, thus revealing macroscopic effects of population inversion and self-trapping with different initial states. In particular, the trajectory of the oscillations of the populations in each well shows how the dynamics of the condensates are effected by the presence of dipole–dipole interaction and gauge field.