量子显自极寒来——冷原子研究漫谈

冷原子体系的量子波动性、宏观量子相干性和人工可调控性,使其成为了一个全新的量子体系,其新颖的量子态和奇异物性的研究是国际上具有前瞻性和挑战性的前沿领域。自1995年实现稀薄气体玻色—爱因斯坦凝聚以来,从单组分、简单相互作用的研究逐渐过渡到多组分、复杂多体效应以及自旋—轨道耦合、非厄米、强关联、无序效应等新物理的研究。文章介绍了近几年冷原子方面的研究进展,包括冷原子的相关技术、冷原子在量子精密测量、量子模拟和量子计算方面的重要工作,期望给未来的研究以新启迪。     

超冷原子系综的非高斯纠缠态与精密测量

量子精密测量是基于量子力学的基本原理对特定物理量实施测量,并利用量子效应提高测量精度的交叉科学.随着超冷原子实验技术的发展,超冷原子为量子精密测量提供了一个优异的研究平台.利用发展成熟的量子调控技术,人们可以基于超冷原子系综制备一些新奇的非高斯多粒子纠缠态.基于多体量子干涉,利用这些非高斯纠缠态作为输入,可以实现超越标准量子极限的高精度测量.本文简要综述这一研究领域的进展.     

单原子激光操控研究进展

文章评述了激光操控单个中性原子研究方面的进展,报道了作者及其合作者近年来在单原子激光囚禁与冷却、单原子量子比特的相干转移、单原子物质波干涉仪、两个异核原子的受控碰撞等方面所取得的最新研究结果,最后对未来发展进行了展望。     

光缔合产生超冷分子及其光谱测量

超冷分子的产生对于量子信息、分子物理和分子化学具有重要的意义。本文通过介绍超冷分子的研究进展,主要分析了光缔合产生超冷分子的特点与物理机制,详细介绍了光缔合产生冷分子过程中的光谱测量方法。     

超冷极性分子

目前对超冷原子的研究已经从最初的原子分子物理扩展到了物理的很多分支.极性分子可以将电偶极相互作用引入到超冷体系,同时分子又与原子类似,可以灵活地被光和其他电磁场操控,因而很多理论工作都预言了超冷极性分子在超冷化学、量子模拟和量子信息等领域会有重要的应用.但由于超冷基态分子的制备非常困难,如何把超冷物理从原子发展到分子还是一个方兴未艾的课题.过去的10年间,各种分子冷却技术都取得了很大突破,本文回顾了这些进展,并着重介绍了基于异核冷原子的磁缔合结合受激拉曼转移这一技术,该技术在制备高密度的基态碱金属超冷极性分子上取得了较大的成功.本文也总结了超冷极性碱金属分子基本碰撞特性研究的一些实验结果.     

从费米原子到配对超冷分子

自从1995年以来，实验物理学家已经在一系列玻色原子气系统中实现了玻色—爱因斯坦凝聚(BEC)，它们是^1H，^7Li，^23Na，^85Rb和^87Rb等等，这些玻色原子具有整数自旋量子数，与玻色原子相对应的是费米原子，它们具有半整数的自旋值，例如^40K。即使在非常接近绝对零度的低温下，费米原子气也不可能凝聚到单一量子态：每一个费米原子所     

Λ型原子-分子三能级系统的分子转化率问题

利用解析和数值的方法对Λ型原子-分子三能级系统的量子动力学行为进行了详细研究，同时对该系统中分子转化率进行了研究.结果发现，不同的系统初态对转化率有比较大的影响，理想情况下，在初始态为原子态且在两个拉比频率相等时，可以得到较高的分子转化率，而光场的失谐会造成转化率的降低；初始态为暗态时，分子转化率为一常数，光场的失谐会增大转化率.     

分子光学及其应用前景

随着原子光学的快速发展，一门新兴的有关研究中性分子与电场、磁场和光场等物质相互作用及其冷却、囚禁、操控与应用的学科——“分子光学”正在逐步形成．文章首先就分子光学的学术内涵及其研究内容作一简单类比与讨论；其次，就冷分子束的产生与超冷分子样品的实验制备、超冷分子物理与光谱学、非线性与量子分子光学的研究及其最新进展进行简要综述．最后，就分子光学的应用前景进行了展望．     

超快强激光驱动的原子分子电离

强场电离是超快强激光与物质相互作用时发生的基本物理过程。强场驱动原子分子的电离电子动力学过程发生在一个光学振荡周期以内,是在阿秒时间尺度上研究电子超快动力学的典范。不仅如此,强场驱动下的超短电子束还为探测原子分子的结构及其超快动力学提供了重要的技术手段。文章首先简要阐述了超快强光场中原子分子电离的基本物理图像,在此基础上,介绍了近年来基于强场电离电子开展的超快过程研究的几个例子,最后简要讨论了强场电离研究的未来可能发展方向。     

原子相干对光缔合形成分子的影响

用量子统计方法,讨论了原子相干对超冷两态原子经光缔合形成超冷分子的影响.结果表明,在原子相干的作用下,光缔合形成的分子数随时间做近周期减幅振荡.原子相干对光缔合过程的暂态阶段影响强烈,而分子始终保持sub-Poisson统计分布.     

Interplay of the Staggered and Three-Body Interaction Potentials on the Quantum Phases of a Spin-1 Ultracold Atom in an Optical Lattice

The interplay of the staggered and the three-body interaction potentials on the quantum phases of a spin-1 Bose Hubbard model using a mean field approximation (MFA) is studied. In the antiferromagnetic (AF) case, a smaller value of the staggered potential (SP) results in the charge and the spin density wave ordering along with the Mott insulator (MI) and the staggered superfluid (SSF) phases. While the competition between two types of the potential leads to the stabilization of the higher order MI and charge density wave (CDW) phases with increasing three-body interaction strength. Further, the spin eigenvalue and nematic order parameters are calculated to scrutinize the spin singlet-nematic formation in the MI and the CDW phases and spin population fractions to analyze the nature of the SSF phase. A signature of the spin density wave (SDW) pattern is also observed in the gapped phase lobes. In case of a purely three-body interaction, the third and higher order insulating lobes become dominant with increasing staggered potential strength. Subsequently, all MFA phase diagrams are then nicely corroborated with the analytical results obtained using a perturbative expansion corresponding to the AF and ferromagnetic cases.     

Novel Quantum Phases of Ultracold Bosonic Atoms in Honeycomb Optical Lattice

We study the quantum phase transition of ultracold atoms in the honeycomb optical lattice. The Hamiltonian of ultracold bosonic atoms in the honeycomb optical lattice is derived. We take the mean-field approximation and further solve the Hamiltonian with the numerical diagonalization method. We obtain the phase diagram and find that the Mort-insulator （MI）, density wave （DW） and modulated superfluid （MS） phases appear. Furthermore, the phase diagram is analyzed according to the order parameter and the average number of particles.     

Unconventional Energy Bands and Chirality of Ultracold Atoms in Trilayer Honeycomb Lattice

We investigate ultracold fermionic atoms in the trilayer honeycomb lattice. In the low energy approximation, we derive an effective Hamiltonian for pseudospins. The energy spectrum shows a cubic form of the wavevector and is gapless. The quasiparticles and quasiholes are ehiral and show Berry＇s phase π when the wavevector adiabatically evolves along a closed circle, Furthermore, the experimental detection of the energy spectrum is proposed with Bragg scattering techniques.     

Unconventional Energy Bands and Chirality of Ultracold Atoms in Trilayer Honeycomb Lattice

We investigate ultracold fermionic atoms in the trilayer honeycomb lattice. In the low energy approximation, we derive an effective Hamiltonian for pseudospins. The energy spectrum shows a cubic form of the wavevector and is gapless. The quasiparticles and quasiholes are chiral and show Berry's phase π when thewavevector adiabatically evolves along a closed circle. Furthermore, the experimental detection of the energy spectrum is proposed with Bragg scattering techniques.     

Vacuum polarization in muonic atoms: the Lamb shift at low and medium Z

In muonic atoms the Uehling potential (an effect of a free electronic vacuum polarization loop) is responsible for the leading contribution to the Lamb shift causing the splitting of states with Δn=0 and Δl≠0. Here we consider the Lamb shift in the leading nonrelativistic approximation, i.e., within an approach based on a certain Schr?dinger equation. That is valid for low and medium Z as long as (Zα)²≪1. The result is a function of a few parameters, including κ=Zαm_μ/m_e, n and l. We present various asymptotics and in particular we study a region of validity of asymptotics with large and small κ. Special attention is paid to circular states, which are considered in a limit of n≫1.     

单原子冷却及光学操控的实验进展

文章综述了基于原子冷却与俘获的单原子制备及其光学操控的基本实验原理及实验进展,并介绍了单原子制备及光学操控在量子寄存器、单光子源、原子－光子纠缠等方面的应用,简述了文章作者所在研究小组在单原子制备和光学操控方面的实验进展.     

单原子冷却及光学操控的实验进展

文章综述了基于原子冷却与俘获的单原子制备及其光学操控的基本实验原理及实验进展,并介绍了单原子制备及光学操控在量子寄存器、单光子源、原子-光子纠缠等方面的应用,简述了文章作者所在研究小组在单原子制备和光学操控方面的实验进展.     

The lifetime of the dimuon atom

Summary The weak decay of a muon in the ground state of a dimuon atom is analysed. Although the two muons are correlated by Fermi-Dirac statistics, it is shown that, in marked contrast to the seemingly analogous case of neutron beta-decay in³H, statistics have no effect on the muon decay rate. The distinction between the two cases is discussed. To speed up publication, the author of this paper has agreed to not receive the proofs for correction.