光子四维量子态隐形传输

多维量子纠缠态比二维纠缠态可加载更多的信息,多维量子系统是量子信息处理中一个很重要的资源.本文采用已实现的光子四维纠缠态,给出了光子四维量子态的张量表达式,并描述了四维量子态隐形传输的一般表示方法;通过讨论光子四维量子态系统的量子通道参数矩阵和测量矩阵的特性,得到实现完全传输和非零概率传输的充要条件.最后,本文给出在多种量子通道下的四维态的量子隐形传态方案,这一过程在张量分析表示下十分清晰明了.     

变光外差为电外差的双频激光探测

演示一种双频激光位移探测系统,阐述光载波激光雷达的概念。由单块非平面环形腔固体激光器和声光调制器产生100MHz载波频率的双频激光束,作为探测光束,经过光路收发系统,探测位于电动导轨上目标的位移变化,信号处理部分采用高速光电探测器响应后信号的电子外差解调方式,位移量的获得通过高频锁相放大器解算参考光束与信号光束的相位差并计算获得。通过双频激光把光学外差探测变为了电子外差探测,系统重复误差小于3%。系统在利用无线电雷达信号处理方式的同时,保留了激光探测的优点,位移测量系统具有良好的重复性。     

低气压条件下氢气潘宁放电的模拟分析

为更好地理解低气压、弱电离条件下潘宁离子源放电过程中离子和电子的动力学行为, 通过建立二维轴对称模型, 采用粒子模拟与蒙特卡罗相结合(PIC/MCC)的方法, 考虑了电子与氢气之间的弹性碰撞、激发、电离以及氢原子、离子之间的弹性碰撞和电荷交换等过程, 对微型氢气潘宁离子源放电和引出过程进行了数值研究. 考察了磁场位形、壁面二次电子发射系数、引出电压和充气压力对放电过程的影响, 得到了实验中难以诊断得到的放电腔内电子与离子数密度分布, 阳极电流、引出极离子电流、单原子氢离子比例和双原子氢离子比例等宏观参数与实验结果相一致. 通过仿真使得对氢气潘宁放电机制的研究从定性过渡到定量, 这对于潘宁离子源的设计和改进具有重要意义. 关键词： 潘宁放电 氢气 粒子模拟 蒙特卡罗     

Effects of SiNx on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors

SiN_x is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN_x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiN_x films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results.     

激光功率和能量计量技术的现状与展望

功率和能量是激光器的两个基本参数,激光功率和能量测量一直是激光参数计量中最基础的测量工作.总结了美国标准技术研究院(NIST)、英国国家物理实验室(NPL)以及中国国家计量院(NIM)在激光功率能量计量方面的技术现状,重点介绍了国防科工委光学计量一级站激光功率能量计量方面已具备的条件,详细说明了所采用的测量原理以及所达到的测量范围和测量不确定度等技术指标.提出了激光功率和能量计量的发展趋势和发展方向.     

Coupling Distant Spins of Surface-State Electrons by Manipulating Their Collective Vibrations

The system of electrons on liquid helium is an interesting candidate to implement quantum computation, due to the long coherence times of the qubits encoded by the electronic spins. In order to implement the quantum logic operations between the spins, we propose here a configuration, similarly to the cooled ions in a trap, to couple the distant electrons via manipulating their center of mass （CM） vibrations. First, we show that the electrons could be confined in a common harmonic oscillator potential by using an electrostatic field. Then, with a single current pulse （applied on the micro-electrode below the liquid helium） the distant electronic spins can be coupled simultaneously to the CM mode. Finally, by adiabatically eliminating the CM mode, effective interaction between the distant spins is induced for implementing the desired quantum computing.     

2-甲基-1,3-顺丁二烯在Rh(Ⅰ)催化下与苯甲醛反应机理的研究

采用密度泛函方法(DFT)研究了2-甲基-1,3-顺丁二烯在Rh(Ⅰ)催化下与苯甲醛反应生成高烯丙基醇的反应机理.在B3LYP/6-31+G*水平上优化了反应过程中所有反应物、过渡态、中间体以及产物的几何构型,通过能量和振动分析确认了过渡态的真实性.并且在相同基组水平上应用自然键轨道(NBO)、前线轨道理论和分子中的原子(AIM)理论分析了这些化合物的成键特征和轨道间的相互作用.报道了可能的反应通道IA:Re→ IMA1→TSA1→IMA2→ IMA3→ TSA2→IMA4→IMA5→ TSA3→IMA6→PA;IB:Re→IMB1→TSB1→IMB2→IMB3→TSB2→ IMB4→ IMB5→TSB3→ IMB6→ PB,根据相对能量分析确定反应通道IB具有相对较低的活化能,是反应的主通道,与实验结果一致.     

Determining Nuclear Form factor for Detection of Dark Matter in Relativistic Mean Field Theory

In this work, we derive the nuclear form factor for the spin-independent collision between the WIMPs and nucleus in terms of the relativistic mean field (RMF) theory. Comparison with the traditional form factors which are commonly used in literature is given and it is found that our results are slightly above that of the 2PF model by 4% to 8%, but deviate from the Helm form factor by 15% to 25% for the whole recoil energy spectrum of 0 ∽ 100keV. Moreover, taking Xe and Ge as examples, we show the dependenceof the form factor on the recoil energy.     

污水处理厂及受纳水体样品的三维荧光光谱解析

采用三维荧光光谱表征了污水厂各处理单元及受纳水体上下游的样品,应用平行因子分析方法获得了样品中各主成分的激发发射光谱图及荧光强度得分矩阵。结果表明,类蛋白质和类富里酸物质是污水厂和受纳水体样品的主要荧光组分。污水厂进水样品的类蛋白质荧光较强,后续各处理单元样品的荧光强度显著下降。受纳水体上游样品的类蛋白质荧光较弱,经过城区各取样点的类蛋白质荧光显著增加,而污水厂排放口上游荧光强度则显著高于下游。类蛋白质荧光强度得分可与样品COD值建立相关曲线,污水厂与受纳水体样品的相关系数分别为0.930和0.913,类蛋白质荧光可以反映样品点的有机污染程度。该研究为污水处理厂的运行及其对受纳水体影响提供了新的思路和方法。     

Thermodynamic equilibrium between locally excited and charge-transfer states through thermally activated charge transfer in 1-(pyren-2′-yl)-o-carborane

Reversible conversion between excited-states plays an important role in many photophysical phenomena. Using 1-(pyren-2′-yl)-o-carborane as a model, we studied the photoinduced reversible charge-transfer (CT) process and the thermodynamic equilibrium between the locally-excited (LE) state and CT state, by combining steady state, time-resolved, and temperature-dependent fluorescence spectroscopy, fs- and ns-transient absorption, and DFT and LR-TDDFT calculations. Our results show that the energy gaps and energy barriers between the LE, CT, and a non-emissive ‘mixed’ state of 1-(pyren-2′-yl)-o-carborane are very small, and all three excited states are accessible at room temperature. The internal-conversion and reverse internal-conversion between LE and CT states are significantly faster than the radiative decay, and the two states have the same lifetimes and are in thermodynamic equilibrium.

Reversible conversion between excited-states is key to many photophysical phenomena. We studied the equilibrium between LE and CT states by time-resolved and temperature-dependent fluorescence, fs- and ns-transient absorption, and LR-TDDFT calculations.