量子算法的NMR实现方法

量子计算机是一种以量子耦合方式进行信息处理的装置[1 ] 。原则上 ,它能利用量子相干干涉方法以比传统计算机更快的速度进行诸如大数的因式分解、未排序数据库中的数据搜索等工作[2 ] 。建造大型量子计算机的主要困难是噪音、去耦和制造工艺。一方面 ,虽然离子陷阱和光学腔实验方法大有希望 ,但这些方法都还没有成功实现过量子计算。另一方面 ,因为隔离于自然环境 ,核自旋可以成为很好的“量子比特” ,可能以非传统方式使用核磁共振 (NMR)技术实现量子计算。本文介绍一种用NMR方法实现量子计算的方法 ,该方法能够用比传统方法少的步骤解决一个纯数学问题。基于该方法的简单量子计算机使用比传统计算机使用更少的函数“调用”判断一未知函数的类别。     

Novel hexadentate imidazolium salts in the rhodium-catalyzed addition of arylboronic acids to aldehydes

Four novel hexadentate imidazolium salts were synthesized from hexakis(bromomethyl)benzene and 1-substituted imidazole. The arylation of aldehydes with arylboronic acids was effected conveniently and in high yields by a catalyst system generated in situ from these hexadentate imidazolium salts, [Rh(COD)Cl]₂ and a base.     

在高密度下核物质的色超导性

建立了相变热力学理论和场论的关系. 强调在量子场论中必须引进序参量场， 则相变的讨论就类似于Goldstone bosons 的产生. 如果只讨论一级相变， Goldstone bosons场就足够了; 如果要讨论二级相变， 则必须讨论一系列的场， 这些场构成一个对称群的表示. 另外, 也将这一思想用到色超导中. In this paper we built a relation between the thermodynamical theory of the phase transition and field theory. We emphasized that in the quantum field theory we have to introduce the order parameter fields. Then the discussion of the phase transition is closed to the creation of the Goldstone bosons. If we only discuss the first order transition, the Goldstone bosons fields are sufficient. If we want to discuss the second order transition, we have to discuss a set of fields that constructs a representation of a symmetry group. We also apply this concept to color superconductivity.     

Spin polarization effect for Tc2 molecule

Density functional method (DFT) (B3p86) of Gaussian98 has been used to optimize the structure of the Tc_2 molecule. The result shows that the ground state for Tc_2 molecule is an 11-multiple state and its electronic configuration is {}^{11}Σ_g^-, which shows the spin polarization effect of Tc_2 molecule of a transition metal element for the first time. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions of higher energy states. So, that the ground state for Tc_2 molecule is an 11-multiple state is indicative of the spin polarization effect of Tc_2 molecule of a transition metal element: that is, there exist 10 parallel spin electrons. The non-conjugated electron is greatest in number. These electrons occupy different spacious tracks, so that the energy of Tc_2 molecule is minimized. It can be concluded that the effect of parallel spin of the Tc_2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell--Sorbie potential functions with the parameters for the ground state {}^{11}Σ_g^- and other states of Tc_2 molecule are derived. Dissociation energy D_e for the ground state of T_{c2} molecule is 2.266eV, equilibrium bond length R_e is 0.2841nm, vibration frequency ω_e is 178.52cm^{-1}. Its force constants f_2, f_3, and f_4 are 0.9200aJ·nm^{-2}, --3.5700aJ·nm^{-3}, 11.2748aJ·nm^{-4} respectively. The other spectroscopic data for the ground state of Tc_2 molecule ω_eχ_e, B_e, α_e are 0.5523cm^{-1}, 0.0426cm^{-1}, 1.6331×10^{-4}cm^{-1} respectively.     

Spectral shifts and spectral switches in diffraction of ultrashort pulsed beams passing through a circular aperture

Based on the Fourier transform method, a simple closed-form expression for the on-axis power spectrum of ultrashort Gaussian pulsed beams in diffraction at a circular aperture is derived, which permits us to study spectral changes both analytically and numerically. It is shown that for diffracted pulsed beams there exist spectral red and blue shifts, spectral narrowing, and spectral switches in the near field. The aperture diffraction plays an important role in spectral switching, but both the truncation parameter and bandwidth (or equally, Fourier transform limited pulse duration) affect the behavior of spectral switches.     

The polarization property and irradiance distribution of incoherent and coherent Gaussian beam combinations

Based on the beam coherence-polarization (BCP) matrix, the polarization property of coherent and incoherent Gaussian beam combinations is studied in detail. The general expressions for the degree of polarization P of the resulting beam in case of incoherent and coherent combinations are derived. It is shown that P is dependent on the incoherent or coherent combination, propagation distance, separation, azimuth of the polarization plane and numbers of beamlets in general. The irradiance distribution of the resulting beam for the coherent cases depends on the azimuth of the polarization plane of beamlets. However, for the incoherent case it does not.     

高功率LDA紧密侧面抽运Nd:YLF两级双程离轴放大系统实验研究

 介绍了一台10mm口径两级双程离轴放大系统，实现了对5mm×5mm口径光束的激光放大，耦合系统采用高功率LDA紧密侧面直接抽运棒状Nd:YLF方式。分析并实验研究了在不同抽运电流、放大脉冲与放大器LDA抽运时刻的不同延时及不同注入能量条件下，放大系统及光束每次放大时放大特性的规律。实验得到：在放大系统5mm×5mm软光阑处注入1.58mJ能量时，放大系统可输出129.2mJ能量，能量提取效率达到19.5%，满足该系统的设计指标。     

AGSM光束在自由空间中的传输

 用矩阵方法研究了有扭曲的各向异性高斯-尔模型（AGSM）光束通过自由空间的传输。给出了光束参数的解析传输公式和详细数值计算结果，说明AGSM光束的传输特性以及扭曲因子和空间相关长度的影响。     

超短脉冲贝塞尔光束的非近轴效应对传输的影响

 对超短脉冲贝塞尔光束在近轴近似和非近轴情况下自由空间中的传输作了研究。结果表明，其空间波形在传输中保持贝塞尔形状不变，不受非近轴效应影响；然而当空间参数较大时，非近轴效应影响超短脉冲贝塞尔光束的时间波形。     

分散剂对RF凝胶掺钛过程的影响

 以间苯二酚、甲醛和经分散的纳米钛粉为反应前体，利用物理掺杂方法研究了掺钛RF凝胶的制备工艺，并在凝胶过程中以zeta电位 粒径分布测试仪对溶液的粒径分布进行分析测试。实验发现六偏磷酸钠对纳米钛粉的分散性最好，掺杂后凝胶时间明显缩短；分散剂种类和用量对凝胶时间有较大影响，其用量为纳米钛粉量的50~100倍为宜。