GaAs半导体量子箱中电子的斯塔克效应

在有效质量近似下,利用变分法研究了在GaAs半导体量子箱中电子能量的斯塔克效应.结论表明:电场平行于量子箱的中心轴时,斯塔克能移只与量子箱高度有关;电场垂直于中心轴时,斯塔克能移仅仅与它的截面尺寸有关.当电场方向与中心轴夹角为任意角时,斯塔克能移与高度和截面都有关.同时在低场和高场极限下,理论上分析了电场大小和量箱尺寸对斯塔克能移的影响.     

GaAs半导体量子箱中电子的斯塔克效应

在有效质量近似下,利用变分法研究了在GaAs半导体量子箱中电子能量的斯塔克效应.结论表明：电场平行于量子箱的中心轴时,斯塔克能移只与量子箱高度有关;电场垂直于中心轴时,斯塔克能移仅仅与它的截面尺寸有关.当电场方向与中心轴夹角为任意角时,斯塔克能移与高度和截面都有关.同时在低场和高场极限下,理论上分析了电场大小和量箱尺寸对斯塔克能移的影响.     

非简并拉曼过程中交流斯塔克位移对场熵和缠绕的影响

利用修正后的哈密顿量计算非简并拉曼过程中双模光场场熵的演化,并研究了原子能级的交流斯塔克位移对场熵演化和原子场之间的缠绕的影响.结果显示:交流斯塔克位移的存在使双模光场的熵的演化呈现出较完美的周期性,并且演化的周期以及原子光场缠绕的程度均受交流斯塔克位移的影响. 关键词： 非简并拉曼过程 交流斯塔克位移 双模光场 场熵 原子光场纠缠度     

三维氢原子斯塔克效应中能量一级修正公式的求解

进一步简化了三维氢原子斯塔克效应微扰矩阵元的普遍公式,并给出了三维氢原子斯塔克效应中任意态能量的一级修正公式.     

二维氢原子斯塔克效应能量一级修正的通式

推导出了二维氢原子斯塔克效应微扰矩阵元的通式,并且给出了二维氢原子斯塔克效应中任意态能级一级修正的通式.     

氢原子斯塔克效应的能级分裂规律

根据简并情况下的微扰理论和n=1,2,3,4能级对应的久期方程的规律,推出任意状态下氢原子斯塔克效应中的久期方程行列式中各矩阵元的分布规律,并找出了氢原子一级斯塔克效应在电场中的能级分裂规律.     

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求出均匀外电场作用下三层球状纳米系统电子的能量和波函数，讨论了外电场和样品线度对斯塔克能级移动的影响. 关键词： CdS/HgS/CdS球状纳米系统 斯塔克效应 能量和波函数     

氢原子的一级斯塔克效应的能级分裂和简并度

我们以表格的形式给出了氢原子的一级斯塔克效应的能级分裂及简并度的情况,并通过与以往文献中的理论计算比较得到了验证.最后在抛物坐标下,通过对氢原子一级斯塔克效应能级分裂一般表达式的分析,给出了相邻两条能级间距满足1.5neεa的理论支持.     

非简并拉曼过程中交流斯塔克位移对腔场谱的影响

研究了原子与双模光场非简并拉曼耦合过程中交流斯塔克位移对腔场谱的影响.给出了原子处于基态且双模初始场为光子数态、相干态和压缩真空态时光谱结构的数值结果.发现数态光场在弱场条件下每模腔场谱都是三峰结构，在强场条件下则为双峰或单峰结构，相干态和压缩真空态光场的腔场谱在弱场或强场条件下都是双峰结构.随着斯塔克位移参数的变化,双峰的高度此长彼消. 关键词： 交流斯塔克位移 非简并拉曼过程 腔场谱     

斯塔克效应对两模双光子J-C模型腔场谱的影响

研究了斯塔克(Stark)效应对两模双光子Jaynes-Cummings(J-C)模型腔场谱的影响,推导计算出了腔场处于光子数态时腔场谱的计算公式和数值结果,讨论了斯塔克效应和初始场强对腔场谱的影响。发现斯塔克效应在弱场条件下对腔场谱线的频率和强度都有明显的影响,破坏了谱结构的对称性,使两模的谱线更加丰富。初始场较强时斯塔克效应对谱线的影响较弱。模Ⅰ为真空场、模Ⅱ初始场强递增时,斯塔克效应使模Ⅱ的高频峰受到较强的抑制作用,其低频峰在初始场较弱时受到抑制,初始场较强时又有强化作用,初始场更强时,模Ⅱ的谱线退化为经典的共振荧光谱,与无斯塔克效应的情况基本相同。     

Stark spectra of Rydberg states in atomic cesium in the vicinity of n=18

The Stark structures in a cesium atom around n=18 are numerically calculated. The results show that the components of 20D states with a small azimuthal quantum number |m| shift upward a lot, and those with a large |m| shift downward a little within 1100 V/cm. All components of P states shift downward. Experimental work has been performed in ultracold atomic cesium. Atoms initially in 6P3/2 state are excited to high-n Rydberg states by a polarization light perpendicular to the field, and Stark spectra with |m|=1/2,3/2,5/2 are simultaneously observed with a large linewidth for the first time. The observed spectra are analyzed in detail. The relative transition probability is calculated. The experimental results are in good agreement with our numerical computation.     

Magnetic hyperfine field of129I impurities in Pd2MnSb

Conclusions In the Heusler alloy Pd₂MnSb (Z) agreement has been found between the experimental values of magnetic hyperfine fields of 5sp shell impurities Z that substitute Sb and the theoretical predictions of Blandin and Campbell |2|. The decrease of the field when the 5sp shell is nearly full lends support to conduction electron polarization models based on the Daniel Friedel |4| type of theory. In view of these results, the rise of the field of 5sp impurities in iron right up to shell closure remains puzzling.     

Electric field dependent mobility edge and theory of the breakdown of the integer quantum Hall effect

We discuss the microscopic mechanism for the onset of dissipation in a quantum Hall system. Based on general results on the time dependence of the states in a disorder-broadened Landau band in the presence of a macroscopic electric field E, it is found that the mobility edges move from the band center towards the band tails when |E| is increased, in agreement with experiments. Since in real samples, |E| is space dependent, the mobility edges are also space dependent. Dissipation (i.e. breakdown of the quantum Hall effect) sets in at points (x, y), where |E(x, y)| has the value for which a mobility edge attains the Fermi energy. This value depends on the disorder potential and on the filling factor. Inside a sample, the conductivities depend on |E(x, y)| and hence on space. We discuss experimental applications, including dissipation in opposite corners of a Hall bar and related breakdown phenomena.     

Analysis of a teleportation scheme involving cavity field states in a linear superposition of Fock states

We analyse a teleportation scheme of cavity field states. The experimental sketch discussed makes use of cavity quantum electrodynamics involving the interaction of Rydberg atoms with superconducting (micromaser) cavities as well as with classical microwave (Ramsey) cavities. In our scheme the Ramsey cavities and the atoms play the role of auxiliary systems used to teleport a field state, which is formed by a linear superposition of vacuum |∅〉 and the one-photon state |1〉, from a micromaser cavity to another.     

液氦温度(4.2K)下LaOBr:Ce3+,Tb3+粉末的电子顺磁共振研究

本文研究了LaOBr:Ce+3,Tb3+粉末在液氦温度(4.2K)下的电子顺磁共振,并且进行了晶体场理论计算,理论与实验结果符合得较好,这表明Ce,Tb离子取代了基质中La离子形成发光中心。     

原子运动与场频率变化操控下的场熵演化及量子态制备

在旋波近似下,同时考虑原子运动和光场频率随时间作正弦函数变化,研究了二能级原子与单模辐射场相互作用系统中场的量子约化熵的演化规律.运用数值计算的方法分别给出了在不考虑原子的运动和考虑原子的运动的情况下场熵随时间的演化曲线,讨论了原子运动、场模结构、场频率的幅值和角频率变化对场熵的影响.根据Schmidt分解定理,解析制备了光场与原子的纠缠态、光场偶数态及原子相干叠加态,获得了调控和制备上述量子态的系统参量.研究结果表明:场熵的演化受场频率变化的调制,场频率变化的幅值增大会削弱场与原子的相互作用,场熵演化的周期性与场频率变化一致|原子的运动导致了场熵演化周期加倍|在场频率变化的角频率一定的情形下,场熵演化规律与场模结构参量的奇偶性有关|无论原子运动与否,都可周期性制备场-原子的近似EPR态.     

不同方向外磁场下海森堡自旋链的热纠缠

研究了两量子比特的海森堡XXX自旋链分别处于x方向和y方向均匀外磁场时系统的纠缠特性,并用负度N来度量。得到纠缠度N的解析表达式,并在此基础上进行数值计算。仔细讨论了磁场B、温度T和自旋耦合系数J对纠缠度N的影响。结果表明：纠缠度N会随着磁场|B|和温度T的增大而减小,但会随着自旋耦合系数J的增大而增大。另外,增大的J还会使临界磁场|Bc|和临界温度Tth变大。所以,我们可以通过调节B、T和J来控制热纠缠,这对固态系统中通过构建和选择参数调整系统的纠缠度具有一定的作用和意义。研究还发现,加在x方向均匀外磁场和加在y方向均匀外磁场对两量子比特的海森堡XXX自旋链的作用效果是一样的。     

An analysis of the folded waveguide: a compact waveguide launcherfor ICRF heating

Theoretical and experimental investigations of the folded waveguide launcher as proposed for use in the ion-cyclotron range of frequencies (ICRF) heating of tokamak plasmas are presented. Theoretical results include an analysis of the folded waveguide using Ritz's method to obtain various field quantities. The cutoff wavenumbers from this analysis are within 10% of those calculated using an unfolded equivalent rectangular waveguide model. Measurements of cavity resonances for a scale-model ICRF-folded waveguide with a cutoff frequency of 2.4 GHz also agree closely with those calculated using an unfolded equivalent model. An unfolded equivalent waveguide model is used to evaluate the properties of an inductive strip placed in the folded waveguide. Applying variational analyses provides upper and lower bounds to the reflection magnitude |S₁₁| that are in good agreement with measured values. Polarizing plates (which have been proposed to increase the on-axis directivity of the radiated power) are modeled using an unfolded equivalent waveguide. A variational analysis is used to determine an upper-bound value of |S₁₁| in air due to a polarizing plate inside a matched folded waveguide. Measured values are found to be within 3% of the calculated values, with |S₁₁|>0.95 for frequencies between 2.5 and 4.5 GHz     

Coherent control of a V-type three-level system in a single quantum dot

In a semiconductor quantum dot, the IIx and IIy transitions to the polarization eigenstates, |x> and |y>, naturally form a three-level V-type system. Using low-temperature polarized photoluminescence spectroscopy, we have investigated the exciton dynamics arising under strong laser excitation. We also explicitly solved the density matrix equations for comparison with the experimental data. The polarization of the exciting field controls the coupling between the otherwise orthogonal states. In particular, when the system is initialized into \Y>, a polarization-tailored pulse can swap the population into |x>, and vice versa, effectively operating on the exciton spin.     

非均匀外磁场下海森堡自旋链的热纠缠

研究了两量子比特海森堡XXX自旋链处于x方向的非均匀磁场时系统的纠缠特性,并用负度N来度量.得到N的解析表达式,并在此基础上进行数值计算.仔细讨论了均匀磁场B、非均匀磁场b、温度T和自旋耦合系数J对纠缠度N的影响.结果表明:N会随着■和T的增大而减小,但会随着J的增大而增大.同时,增大的J和b还会使临界磁场■和临界温度T_th变大,从而使系统中热纠缠存在的磁场范围和温度范围都变大.这一点在较大磁场和较高温度下需要纠缠具有实际意义.由此,我们可以通过调节B、b、T和J来控制热纠缠,这对固态系统中通过构建和选择参数调整系统的纠缠度具有一定的作用和意义.