Magnetic trapping of rare-earth atoms at millikelvin temperatures

The ability to create quantum degenerate gases has led to the realization of Bose-Einstein condensation of molecules, atom-atom entanglement and the accurate measurement of the Casimir force in atom-surface interactions. With a few exceptions, the achievement of quantum degeneracy relies on evaporative cooling of magnetically trapped atoms to ultracold temperatures. Magnetic traps confine atoms whose electronic magnetic moments are aligned anti-parallel to the magnetic field. This alignment must be preserved during the collisional thermalization of the atomic cloud. Quantum degeneracy has been reached in spherically symmetric, S-state atoms (atoms with zero internal orbital angular momentum). However, collisional relaxation of the atomic magnetic moments of non-S-state atoms (non-spherical atoms with non-zero internal orbital angular momentum) is thought to proceed rapidly. Here we demonstrate magnetic trapping of non-S-state rare-earth atoms, observing a suppression of the interaction anisotropy in collisions. The atoms behave effectively like S-state atoms because their unpaired electrons are shielded by two outer filled electronic shells that are spherically symmetric. Our results are promising for the creation of quantum degenerate gases with non-S-state atoms, and may facilitate the search for time variation of fundamental constants and the development of a quantum computer with highly magnetic atoms.     

单模真空场-耦合双原子系统的量子保真度演化

本文利用全量子理论,研究了单模真空场-耦合双原子系统的量子保真度演化特性。结果表明,原子与原子之间偶极相互作用的耦合系数、原子与光场之间的耦合系数以及初态时两个原子均处于基态的几率等因素影响着保真度的演化规律。当原子与原子之间偶极相互作用增大时,整个体系的保真度增大,并且演化曲线出现崩溃-回复特征;当原子和光场之间的耦合系数增大时,整个体系的保真度减小,并且演化曲线的周期明显变小;当初态两原子均处在基态的概率增大时,整个体系的保真度增大。     

The entanglement evolution of two coupling two level atoms interacting with a single mode vacuum field in multiphoton Tavis Cummings model

Using multipohton Tavis-Cummings model, the entanglement evolution of two coupling two-level atoms in Bell states interacting with a single-mode vacuum field is investigated by using Negativity. The influences of coupling constants between atoms, the atomic initial states and the photon number of transition on the entanglement evolution of two coupling two-level atoms are discussed. The results obtained using the numerical method show that the entanglement of two atoms is related with coupling constants between atoms, the atomic initial states and the photon number of transition. The two-atom entanglement state will forever stay in the maximum entanglement state when the initial state is .When the initial state of two atoms is , the entanglement of two atoms displays periodic oscillation behavior.and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition. On the other hand, when the initial state is or , the entanglement of two atoms displays quasiperiodic oscillation behavior and its oscillation period decreases with increasing of coupling constant between atoms or the photon number of transition .     

机械合金化Fe70Cu30体系的结构研究

利用XAFS方法对机械合金化Fe70Cu30样品中Fe,Cu原子的局域环境结构随球磨时间的变化情况进行了研究，结果表明，由于Fe和Cu原子分别向fcc的Cu相和bcc的Fe相的扩展，Fe和Cu同时存在于fcc和bcc结构相中，介Fe和Cu原子的局环境结构随球磨时间的级很大判别，球磨2h后，样品中73％的Cu原子在fcc相，27％的Cu原子在bcc相，21％的Fe原子在fcc相，79％的Fe原子在bcc相，球磨5h，fcc相的Cu原子减少到59％，fcc相的Fe原子则略有增加，为29％，球磨10h后，fcc相的Cu原子比例又增加到86％，fcc相的Fe原子也迅速增加到51％，说明大量的Cu原子扩散到bcc的Fe相后诱导其产生fcc结构相变，继续球磨到20h，样品中Cu原子和Fe原子在fcc和bcc相的比例基本保持不变，这些结果说明，在球磨过程中Fe和Cu并未形成均一的固溶体，同时存在着fcc的Cu富集区，fcc的Fe富集区和bcc的Fe富集区。     

F原子与臭氧和甲烷反应机理的量子化学研究

用量子化学从头计算G3和G3MP2方法研究F原子与臭氧和甲烷的反应机理。优化了反应物、产物、中间体和过渡态的几何构型,研究结果表明,F原子与臭氧之间有很强的反应活性,但F原子与甲烷之间的反应活性更强,通过比较,当F原子与臭氧和甲烷竞争反应时,F原子与甲烷之间反应优先,并合理解释了大气中Cl原子是损耗臭氧的主要化学物质,而活性更强的F原子对臭氧损耗较小的原因是F原子被甲烷消耗了。     

Electronic properties and stabilities of methoxy-substituted Lindqvist polyoxometalates [Nb2W4019CH3]3- by DFT

The electronic properties and stabilities of five [Nb2W4O18OCH3]3-isomers have been investigated using a density functional theory method.The results show that the isomer with the methoxy group occupying a bridging position between two tungsten atoms(two tungsten atoms in the plane that contains two niobium atoms) in the [Nb2W4O18OCH3]3-framework is the most stable isomer in acetonitrile.The stability of the one-electron-reduced isomers changes little.The most stable one-electron-reduced isomer has the methoxy group occupying a bridging position between niobium atoms in the [Nb2W4O18OCH3]4-framework.The M-Ob(M = Nb,W;b denotes bridging) bond lengths in anions in which the metal atoms are connected by a methoxy group are longer than those in [Nb2W4O19]4-.The highest occupied molecular orbitals(HOMO) in [Nb2W4O19]4-mainly delocalize over the bridging oxygen atoms of two niobium atoms and two tungsten atoms located in the equatorial plane,and the bridging oxygen atoms on the axial surface.The lowest unoccupied molecular orbitals(LUMO) of [Nb2W4O19]4-are mainly concentrated on the tungsten atoms and antibonding oxygen atoms.Methoxy substitution modifies the electronic properties of the [Nb2W4O18OCH3]3-isomers.The HOMOs in the five isomers formally delocalize over the bridging oxygen atoms,which are distant from the surface containing the methoxy group and four metal atoms.The LUMOs delocalize over the d-shells of the four metal atoms that are close to the methoxy group,and the p-orbitals of oxygen.One-electron reduction occurred at the tungsten atoms,not the niobium atoms.     

TC模型中有耦合的两二能级原子的纠缠度

纠缠度是对被纠缠的子系统之间的关联程度的量度.用冯?诺依曼熵来描述在相干光场中两 耦合二能级原子之间的纠缠度的演化,显示了两二能级原子之间的纠缠度与原子之间的耦合 强度,光场与原子之间的失谐量的大小以及场强有关系.对初始处于贝尔基的两个原子,原 子间耦合的增强和失谐量的增加都将使纠缠度增加,纠缠度振荡的频率增加,而光强的增强 将导致原子间纠缠度的下降.     

2,4,6-三硝基-2,4,6-三氮杂环己酮生成历程的~(15)N示踪原子研究

该文用~(15)N示踪原子对DPT上不同类型的胺基氮原子分别进行标记。有~(15)N标记的DPT在硝解剂中生成的硝解碎片分子与脲或硝基脲进行曼尼希缩合反应生成2,4,6-三硝基-2,4,6-三氮杂环己酮产物,用质谱分析法鉴定反应物和产物中~(15)N原子的分布及丰度。研究结果表明:DPT上两种不同的胺基氮原子所在的硝解碎片分子的反应性是很不相同的。三亚甲基胺基氮原子100％地进入产物分子的4位,而硝基胺基氮原子100％地不进入产物分子。     

相互作用原子BEC诱导的双模光场压缩特性

考虑原子间的相互作用，给出了旋波近似下双模光场与Ⅴ型三能级原子玻色-爱因斯坦凝聚体（BEC）相互作用系统的哈密顿量，求解了系统的动力学方程，研究了原子间的相互作用对光场正交压缩特性的影响.结果表明：原子间的相互作用缩短了光场正交分量的涨落随时间变化的周期.     

Single atoms in the ring lattice for quantum information processing and quantum simulation

We have demonstrated preparing and rotating single neutral rubidium atoms in an optical ring lattice generated by a spatial light modulator, inserting two atoms into a single microscopic optical potential efficiently by dynamically reshaping the optical dipole trap, trapping single atoms in a blue detuned optical bottle beam trap, and confining single atoms into the Lamb-Dicke regime by combining red and blue detuned optical potentials. In combination with the manipulation of internal states of single atoms, the study is opening a way for research in the field of quantum information processing and quantum simulation. In this paper we review the past works and discuss the prospects.     

双模压缩真空态光场作用下耦合双原子的Wigner-Yanase偏态信息

研究了与双模压缩真空态光场作用过程中耦合双原子的Wigner-Yanase偏态信息．结果表明,当光场压缩因子较小时,光场与原子间相互作用和原子间偶极-偶极相互作用共同决定了原子的总Wigner-Yanase偏态信息演化的周期;增强原子间偶极-偶极相互作用,可以抵抗原子的总Wigner-Yanase偏态信息的丢失;光场压缩因子对原子的总Wigner-Yanase偏态信息的丢失起着重要的作用,当光场压缩因子较大时,原子的总Wigner-Yanase偏态信息会完全丢失     

多氯苊化合物分子结构和热力学性质的理论研究

采用密度泛函理论方法,在B3LYP/6-311G**水平上对35个多氯苊化合物的分子几何结构进行了全优化计算,并获得它们在理想气体状态的一些热力学性质参数,研究了这些性质与氯原子数目和位置的关系,根据多氯苊化合物的相对标准生成Gibbs自由能的大小,得到它们的热力学稳定性顺序.结果表明:所有多氯苊分子中除4个氢原子以外的其他原子都在同一平面上.多氯苊最稳定异构体的ΔfHθ及ΔfGθ随Cl原子数目增加而发生的变化与最不稳定异构体不同.具有相同数目氯原子的多氯苊异构体的ΔfHθ和ΔfGθ与氯原子的取代位置有很大的关系,其相对热力学稳定性主要由分子内的处在不同六元环上的邻近Cl…Cl核排斥作用决定.     

Al-Mg-(Si)-(Sc)-(Zr)合金时效初期微结构演化的模拟研究

运用蒙特卡罗方法计算模拟了加入微合金元素Si,Sc和Zr的Al-Mg合金时效初期微结构的演化过程,分析了微结构演化过程中溶质原子偏聚的特征及其与空位的相互作用;对Si,Sc和Zi与空位复合体的尺寸及空位周围原子的概率分布进行讨论,揭示了空位作用的机理.     

基于原子与光场共振相互作用的W态融合

基于腔量子动力学(QED)系统,从N个原子和M个原子的W态中各取1个原子同时送入真空腔场,利用原子与腔场相互作用实现2个W态融合.当原子与腔场发生共振作用后,探测腔场.结果表明:若有1个光子,则初始的2个W态以一定概率融合为(N+M)个原子W态;若腔场中没有光子,则探测飞出2个原子,若2个原子中有1个原子处于激发态,则初始的2个W态以一定概率融合为(N+M-2)个原子W态;若2个原子均处于基态,则余下的(N-1)个原子W态和(M-1)个原子W态仍可按此方案循环融合.     

材料的电输运性质与电子高能级分布研究

讨论了孤立原子、块状材料、薄膜材料、纳米材料的电子高能态分布的特点及其产生这种特点的原因.指出,由于原子物理学学科分工的特点,没有讨论孤立原子的核外电子的能级分布与温度的关系(也无法讨论);而块状材料和薄膜材料的电子高能态之所以分布在表面上,是与其形状有关的,原因在于表面上存在着缺陷原子,而这些缺陷原子周围存在着悬空键,块状材料和薄膜材料的电子能态分布是连续的,这种连续性是由块状材料和薄膜材料单位体积里包含大量的原子造成的;纳米材料的电子能态是不连续的,这种不连续性是由于纳米颗粒本身包含有限的原子个数造成的.同时定性地解释了稳恒电流无趋肤效应而交流电和超导电流产生趋肤效应的物理原因.     

热膨胀系数同弹性模量数学模型分析

为满足超精密加工对精度的要求，从机理角度分析了材料的热膨胀系数和弹性模量，建立了二者关系的数学模型。结果表明：材料热膨胀和材料弹性模量的物理本质都同原子间作用力密勿相关，只是二者的原子间发生作用的起固有别。材料的热膨胀是因温度升高，原子振幅加大，引起原子间斥力增加，平衡距离加大，原子间仍是平衡状态；而弹性模量是两原子受到外力作用，偏离平衡位置，双子间是引力(斥力)状态，该引力(斥力)值同外界作用力平衡。     

半氟化的石墨片电子和磁特性

通过密度泛函理论研究了半氟化石墨片的电子结构和磁性特点,结果发现它是带隙约为1.00 eV的反铁磁间接带隙半导体。由于氟原子对被氟化的碳原子的吸引作用,被氟化的碳原子与未氟化的碳原子分属于两个不同平面,面间距离达到0.286,C-C键长也增加到1.501。通过半氟化,实现了材料由无磁性向反铁磁的转变,并打开了带隙,这预示着在未来的纳米功能材料中可能的应用。     

F,Cl原子与臭氧和甲烷反应机理和反应动力学的理论研究

用量子化学从关计算UMP2（full)方法研究F和Cl原子与甲烷分子和臭氧之间的反应机理，优化了反应物、产物、中间体和过渡态的几何构型，在Gaussian-3(G3)和G3MP2水平计算了它们的能量，研究结果表明：F原子与Cl原子一样与臭氧之间有很强的反应活性，而F原子与甲烷分子反应过程中有氢键生成，键能为3.71KJ/MOL，F原子与甲烷分子之间反应活性比与臭氧分子之间反应活性强。F原子易与甲烷分子生成含有氢键的化合物，且很快分解生成化学性质非常稳定的HF，能同F O3反应竞争，而CL原子甲烷分子反应过程中则无氢键生成现象，且在CL原子与臭氧和甲烷之间竞争反应时，CL原子与臭氧之间反应优先，同时我们还对F和CL原子与甲烷分子臭氧之间反应动力学速率常数进行了计算，我们的理论计算结果能合理地解释大气中CL原子是损耗臭氧的主要化学物质，而活性更强的F原子为什么对臭氧损耗较小的原因。     

Al-Cu-(Si)-(Sc)-(Zr)合金时效初期微结构演化模拟分析

运用蒙特卡罗方法计算模拟加入微合金元素Si,Sc和Zr的Al-Cu合金时效初期微结构的演化过程,分析微结构演化过程中溶质原子偏聚的特征及其与空位的相互作用,讨论Si,Sc,Zi与空位复合体的尺寸及空位周围原子的概率分布。结果表明,Sc原子与空位之间存在较强的相互吸引作用,使得合金中空位的可动性降低,Cu原子赖以扩散的空位急剧减少,从而导致Cu原子簇丛聚程度大幅度降低;微量的Si使Al-Cu-（Si）合金中的空位明显减少,而且Sc与空位的强烈相互作用也使得空位团簇化加剧。     

Controlled exchange interaction between pairs of neutral atoms in an optical lattice

Ultracold atoms trapped by light offer robust quantum coherence and controllability, providing an attractive system for quantum information processing and for the simulation of complex problems in condensed matter physics. Many quantum information processing schemes require the manipulation and deterministic entanglement of individual qubits; this would typically be accomplished using controlled, state-dependent, coherent interactions among qubits. Recent experiments have made progress towards this goal by demonstrating entanglement among an ensemble of atoms confined in an optical lattice. Until now, however, there has been no demonstration of a key operation: controlled entanglement between atoms in isolated pairs. Here we use an optical lattice of double-well potentials to isolate and manipulate arrays of paired (87)Rb atoms, inducing controlled entangling interactions within each pair. Our experiment realizes proposals to use controlled exchange coupling in a system of neutral atoms. Although 87Rb atoms have nearly state-independent interactions, when we force two atoms into the same physical location, the wavefunction exchange symmetry of these identical bosons leads to state-dependent dynamics. We observe repeated interchange of spin between atoms occupying different vibrational levels, with a coherence time of more than ten milliseconds. This observation demonstrates the essential component of a neutral atom quantum SWAP gate (which interchanges the state of two qubits). Its 'half-implementation', the root SWAP gate, is entangling, and together with single-qubit rotations it forms a set of universal gates for quantum computation.