弱相干场耦合腔系统中原子偶极压缩

考虑将3个全同的二能级原子分别囚禁在3个耦合腔中,并且腔场处于弱相干态的情况。利用数值计算方法研究了原子的偶极压缩效应,讨论了腔场间的耦合系数和腔场的强度对原子偶极压缩的影响。研究结果表明:随腔场间耦合增强,压缩效应减弱。另一方面,随弱相干光场强度的加强,原子的偶极压缩效应增强。     

An elementary quantum network of single atoms in optical cavities

Quantum networks are distributed quantum many-body systems with tailored topology and controlled information exchange. They are the backbone of distributed quantum computing architectures and quantum communication. Here we present a prototype of such a quantum network based on single atoms embedded in optical cavities. We show that atom-cavity systems form universal nodes capable of sending, receiving, storing and releasing photonic quantum information. Quantum connectivity between nodes is achieved in the conceptually most fundamental way-by the coherent exchange of a single photon. We demonstrate the faithful transfer of an atomic quantum state and the creation of entanglement between two identical nodes in separate laboratories. The non-local state that is created is manipulated by local quantum bit (qubit) rotation. This efficient cavity-based approach to quantum networking is particularly promising because it offers a clear perspective for scalability, thus paving the way towards large-scale quantum networks and their applications.     

飞灰在单纤维上形成颗粒链的生长和形貌

为了深入研究静电对纤维滤料过滤过程的影响,利用显微镜与CCD摄像技术,实时观测对比了体积平均直径为1.4μm飞灰颗粒在自然、极化和荷电条件下,被直径为20μm的单纤维捕集的过程。自然条件下,迎风面颗粒沉积形成“灌木丛”状颗粒链,并按照纤维捕捉、纤维和颗粒链共同捕捉与颗粒链单独捕捉3个阶段持续增长;背风面初始阶段形成4μm左右的链后便停止增长。极化条件下,形成分叉较少的直链,并具有10μm左右的较均匀间距,直链在平均链长20μm左右开始倒伏;倒伏并顺风拖曳在纤维背风向的长链仍具有较强的颗粒捕捉能力。荷电条件下,虽也能形成直链,但其分布相对不均匀,具有一些分叉;当平均长度为10μm左右颗粒链开始倒塌和断裂,倒塌于迎风面的颗粒链减弱了继续形成直链的能力。     

单神经元PSD控制器在自动送钻模拟加载中的应用

自动送钻实验研究为其在现场的推广应用奠定基础 .针对钻井过程中井况的非线性、不确定性和实时性要求 ,采用单神经元 PSD控制器实现自动送钻模拟加载 .给出了自动送钻实验系统的结构和原理 ,介绍了单神经元 PSD控制器的设计 .实验结果表明 ,单神经元 PSD控制器结构简单 ,易于实现 ,效果明显优于 PID控制器 ,值得推广 .     

Quantum phase transition from a superfluid to a Mott insulator in a gas of ultracold atoms.

For a system at a temperature of absolute zero, all thermal fluctuations are frozen out, while quantum fluctuations prevail. These microscopic quantum fluctuations can induce a macroscopic phase transition in the ground state of a many-body system when the relative strength of two competing energy terms is varied across a critical value. Here we observe such a quantum phase transition in a Bose-Einstein condensate with repulsive interactions, held in a three-dimensional optical lattice potential. As the potential depth of the lattice is increased, a transition is observed from a superfluid to a Mott insulator phase. In the superfluid phase, each atom is spread out over the entire lattice, with long-range phase coherence. But in the insulating phase, exact numbers of atoms are localized at individual lattice sites, with no phase coherence across the lattice; this phase is characterized by a gap in the excitation spectrum. We can induce reversible changes between the two ground states of the system.     

Chernobyl radionuclides in a Black Sea sediment trap

The Chernobyl nuclear power station accident released large quantities of vaporized radionuclides, and, to a lesser extent, mechanically released small (less than 1-10 micron) aerosol particles. The total release of radioactivity is estimated to be out of the order of 1-2 x 10(18) Bq (3-5 x 10(7) Ci) not allowing for releases of the xenon and krypton gases. The 137Cs releases of 3.8 x 10(16) Bq from Chernobyl can be compared to 1.3 x 10(18) Bq 137Cs released due to atmospheric nuclear weapons testing. Chernobyl-derived radionuclides can be used as transient tracers to study physical and biogeochemical processes. Initial measurements of fallout Chernobyl radionuclides from a time-series sediment trap at 1,071 m during June-September 1986 in the southern Black Sea are presented. The specific activities of 137Cs, 144Ce and 106Ru in the trap samples (0.5-2, 4-12 and 6-13 Bq g-1) are independent of the particle flux while their relative activities reflect their rates of scavenging in the order Ce greater than Ru greater than Cs.     

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 .     

循环荷载作用下NaCl溶液对黏土动力特性影响及微观机理分析

针对黏土易与水结合,孔隙溶液环境变化对黏土动力特性有较大影响的问题,使用GDS真/动三轴仪对黏土试样进行模拟交通循环荷载下的分级加载试验,研究不同浓度NaCl孔隙溶液、振动频率对土体应力-应变关系和动弹性模量的影响,分析骨干曲线及弹性模量的发展规律,并结合电镜扫描,分析NaCl溶液浓度和振动频率改变前后试样的孔隙分布规律,得到微观孔径与动力特性的关系。结果表明,随着NaCl溶液浓度和振动频率的升高,应力-应变曲线和动弹性模量曲线呈上移趋势;阻尼比-动应变曲线随振动频率的增加而上升,随NaCl溶液浓度的增加而下降;NaCl溶液浓度升高,水化反应产生的胶体增多,微填充作用可有效减少小孔隙,振动频率增加则使得片状颗粒间距被压缩,层状结构减少,土体更加密实,有效减少大孔隙。研究得出的含NaCl溶液黏土受孔隙溶液浓度与振动频率变化的影响规律,可为研究其他环境下黏土的强度变化提供参考。     

Stationary entanglement of two atoms in a common reservoir

We study the dynamics of two entangled atoms interacting with a common structured reservoir. By means of the exact solution of atomic dynamics, we show a novel quantum interference controlled by the relative phase of initial entangled state of the atoms. The quantum interference has a great influence on trapped excited-state population and stationary entanglement of the atoms. In particular, we construct an explicit condition under which atomic stationary entanglement can grow over their initial value.     

一维Bose-Einstein凝聚中的孤波

 导出了在一维原子玻色-爱因斯坦凝聚(BEC)中,原子被约束在谐和柱形陷阱中时的孤波的有关性质.     

隐式单索夹持式玻璃幕墙承载性能的试验

为研究预应力、玻璃刚度、耐候胶及套管对隐式单索夹持式玻璃幕墙承载性能的影响,进行了试验研究。并在各级预应力以及安装玻璃后施加平面外荷载的条件下研究体系的承载性能,同时进行测试来比较打胶及设置套管前后的承载性能差异。此外,还获取了预应力、玻璃刚度及荷载条件下体系的自振频率。试验结果表明:平面外荷载越大,增加钢索预应力对降低体系变形的作用越小;玻璃自重对体系的自振频率影响远大于刚度的影响;耐候胶及套管对承载性能的影响较小。     

Mass march of termites into the deadly trap.

Carnivorous pitcher plants of the genus Nepenthes are not usually very selective about their prey, catching anything that is careless enough to walk on their slippery peristome, but Nepenthes albomarginata is an exception. We show here that this plant uses a fringe of edible white hairs to lure and then trap its prey, which consists exclusively of termites in enormous numbers. This singular feature accounts for the specialization of N. albomarginata for one prey taxon, unique so far among carnivorous plants.