Cavity cooling of a single atom

All conventional methods to laser-cool atoms rely on repeated cycles of optical pumping and spontaneous emission of a photon by the atom. Spontaneous emission in a random direction provides the dissipative mechanism required to remove entropy from the atom. However, alternative cooling methods have been proposed for a single atom strongly coupled to a high-finesse cavity; the role of spontaneous emission is replaced by the escape of a photon from the cavity. Application of such cooling schemes would improve the performance of atom-cavity systems for quantum information processing. Furthermore, as cavity cooling does not rely on spontaneous emission, it can be applied to systems that cannot be laser-cooled by conventional methods; these include molecules (which do not have a closed transition) and collective excitations of Bose condensates, which are destroyed by randomly directed recoil kicks. Here we demonstrate cavity cooling of single rubidium atoms stored in an intracavity dipole trap. The cooling mechanism results in extended storage times and improved localization of atoms. We estimate that the observed cooling rate is at least five times larger than that produced by free-space cooling methods, for comparable excitation of the atom.     

Observation of entanglement between a single trapped atom and a single photon

An outstanding goal in quantum information science is the faithful mapping of quantum information between a stable quantum memory and a reliable quantum communication channel. This would allow, for example, quantum communication over remote distances, quantum teleportation of matter and distributed quantum computing over a 'quantum internet'. Because quantum states cannot in general be copied, quantum information can only be distributed in these and other applications by entangling the quantum memory with the communication channel. Here we report quantum entanglement between an ideal quantum memory--represented by a single trapped 111Cd+ ion--and an ideal quantum communication channel, provided by a single photon that is emitted spontaneously from the ion. Appropriate coincidence measurements between the quantum states of the photon polarization and the trapped ion memory are used to verify their entanglement directly. Our direct observation of entanglement between stationary and 'flying' qubits is accomplished without using cavity quantum electrodynamic techniques or prepared non-classical light sources. We envision that this source of entanglement may be used for a variety of quantum communication protocols and for seeding large-scale entangled states of trapped ion qubits for scalable quantum computing.     

氦原子基态解析波函数的研究

采用二元泛函变分的方法,求出氦原子基态能量和波函数．该方法比一元泛函变分法得到的结果更接近实验值．计算结果与实验值之差,比用传统方法缩小了１５％．     

用递推法计算锂原子的能量

首先以氢原子的能量为零级近似能量,用微扰法计算了氦原子的2s～4f态能量,然后以氦原子的能量为零级近似能量,用微扰法计算了锂原子2s～4f态的能量。结果与实验值符合得很好。     

The parallel calculation of the ground-state correlation energy of Helium atom

When we use Modified Configuration Interaction method (MCI) to calculate the correlation energy of double-electron systems, for obtaining the higher precision, we always need huge calculations. In order to handle this problem, which will cost much CPU time and memory room if only using a single computer to do it, we now adopt the parallel multisection recurrence algorithm. Thus we can use several CPUs to get the ground-state energy of a Helium atom at the same time. Supported by Opening Foundation of Laboratory of Wavy Spectrum and Atomic and Molecular Physics, Wuhan Institute of Physics, Chinese Academy of Sciences Liu Lianjun: born in 1946, Associate professor     

Prediction of the internal energy contribution of polyethylene

Conformational elasticity theory recently developed has been used to explore the internal energy contribution to the elastic force fe/f as a function of strain for polyethylene (PE). Calculated fe/f values are in good agreement with those obtained experimentally. Results show that the behavior of fe/f is mainly contributed from intramolecular interaction of chemical structure, and that the internal energy contribution is strain-dependent.     

汞原子较高激发态的观测

汞原子处于激发态时,有4种能级状态,只有63P1第一激发态容易观测,而较高激发态则不易观测,本文介绍汞原子较高激发态的观测的实验方法.现象明显,效果很好.     

二能级原子与单模光场相互作用系统的量子场熵演化特性

利用全量子理论,研究了二能级原子与单模相干态光场相互作用系统的量子场熵演化特性;通过数值计算,讨论了光场的平均光子数、光场-原子之间的耦合系数g对量子场熵演化特性的影响.结果表明:量子场熵随时间的演化呈现出周期或非周期性的振荡、崩塌与回复等现象,说明、g对量子场熵演化特性的影响具有非线性的特征.     

Measurement of the conductance of single conjugated molecules

Electrical conduction through molecules depends critically on the delocalization of the molecular electronic orbitals and their connection to the metallic contacts. Thiolated (- SH) conjugated organic molecules are therefore considered good candidates for molecular conductors: in such molecules, the orbitals are delocalized throughout the molecular backbone, with substantial weight on the sulphur-metal bonds. However, their relatively small size, typically approximately 1 nm, calls for innovative approaches to realize a functioning single-molecule device. Here we report an approach for contacting a single molecule, and use it to study the effect of localizing groups within a conjugated molecule on the electrical conduction. Our method is based on synthesizing a dimer structure, consisting of two colloidal gold particles connected by a dithiolated short organic molecule, and electrostatically trapping it between two metal electrodes. We study the electrical conduction through three short organic molecules: 4,4'-biphenyldithiol (BPD), a fully conjugated molecule; bis-(4-mercaptophenyl)-ether (BPE), in which the conjugation is broken at the centre by an oxygen atom; and 1,4-benzenedimethanethiol (BDMT), in which the conjugation is broken near the contacts by a methylene group. We find that the oxygen in BPE and the methylene groups in BDMT both suppress the electrical conduction relative to that in BPD.     

利用两能级原子与相干态腔场相互作用实现纠缠浓缩

根据大失谐条件下原子–腔场相互作用的特点,讨论了一个制备纠缠相干态的方法,提出了一个利用两能级原子与腔场相干态相互作用实现纠缠浓缩的方案。在这个方案中,2个具有相同振幅但有着π相位差的相干光|α〉和|-α〉构成的纠缠态光场被用来作为量子信道,通过利用两能级原子与腔场的相互作用以及两模正交态测量实现了这个纠缠浓缩的过程。结果表明:对于纠缠相干态,无论其初始的纠缠是多么微弱,利用这种方法总有一定的几率可以从部分纠缠态中提取出最大纠缠态。     

汞原子较高激发态的观测

汞原子处于激发态时,有4种能级状态,只有63P1第一激发态容易观测,而较高激发态则不易观测本文介绍汞原子较高激发态的观测的实验方法.现象明显,效果很好.     

两原子结合能实验公式参数的研究

结合物理学中相关的理论知识 ,运用数学分析的方法 ,对凝聚态物理学中结合能实验公式 :U(r) =- arm+brn 中m、n参数进行研究 ,得出n >m的一般性结论。     

氢原子椭圆轨道和能级的简明讨论

对氢原子或类氢离子中电子的椭圆轨道和能量及其量化等给出了一个简明，完善的讨论。     

基态原子的价层电子构型与元素周期表修正

重新确认各种元素基态原子的价层电子构型,进而修正元素周期表。在科顿原子轨道能级图上标出表示各种元素基态原子能量最高能级的点,并将在同一条能级线上且相邻的串联成线段。发现每条这种线段所在闭区间上对应的有序元素组,都有一个简洁的基态原子价层电子构型通式。修正后的元素周期表,周期从3号元素Li开始,周期依据重新确认的各种元素基态原子价层电子构型所出现的周期性界定,不另列镧系和锕系。     

无计算误差的速度测量计算方法

结合编码器自身特点,利用四倍频脉冲电路和相位检测及同步触发技术,采用非整数单位的闸门时间,实现速度测量的简化计算.对不同编码器,采用闸门时间可变的测量方法,给出相应的参数取值,将复杂的乘除运算变换为简单的乘法运算,减少计算工作量,彻底消除计算误差,缩短测量时间,提高速度测量和控制的精度.在石油测井工程车的闭环速度控制系统中获得成功应用.     

双电子原子基态波函数与能量的变分计算

采用了一种线性试探波函数，利用Matlab语言开发了一个运用变分法对三体问题进行计算的软件程序，对双电子原子的基态能量和解析波函数进行了计算。与近年相关文献的研究结果及实验值比较，本文的计算结果误差较小，精度较高。     

Measurement of electric properties of the single supersaturated aerosol droplet

A system for measuring the electric properties of single aerosol droplet is designed and applied to the NaClO4 aerosol droplet in different relative humidity （RH）. The conductance and capacitance are obtained within the whole RH range, especially in the supersaturated state which cannot be acquired from the bulk solution. These results reflect the situation of ions in the droplet macroscopically and supply useful information for other relative study fields, such as crystallogeny and aerography.     

Identification of Na-Ca exchange current in single cardiac myocytes

In cardiac muscle the exchange of intracellular Ca2+ for extracellular Na+ is an important transport mechanism for regulation of the intracellular free Ca2+ concentration [( Ca]i) and hence the contractile strength of the heart. Due to its stoichiometry of greater than or equal to 3:1 Na+/Ca2+ (refs 3,5), Na-Ca exchange is supposed to generate a current across the cell membrane. It is thought that such a current may contribute to cardiac action potential and physiological or pathological pacemaker activity. Although the occurrence of Na-Ca exchange is well documented, a membrane current generated by this transport has not been identified unequivocally. Previous attempts to detect such a current in multicellular preparations, for example, by measuring small current differences after varying the extracellular ionic composition, although providing evidence, did not rule out other possible interpretations. Here we demonstrate that a transient rise in [Ca]i caused by release of Ca from sarcoplasmic reticulum (SR) generates a membrane current in cardiac myocytes. The dependence of this current on the transmembrane gradients for Na+ and Ca2+ and on membrane potential meets the criteria for a current produced by electrogenic Na-Ca exchange. Cyclic activation of this current by release of Ca from the SR can cause maintained spontaneous activity, suggesting that Na-Ca exchange contributes to certain forms of cardiac pacemaking.