Towards a spin-ensemble quantum memory for superconducting qubits

This article reviews efforts to build a new type of quantum device, which combines an ensemble of electronic spins with long coherence times, and a small-scale superconducting quantum processor. The goal is to store over long times arbitrary qubit states in orthogonal collective modes of the spin-ensemble, and to retrieve them on-demand. We first present the protocol devised for such a multi-mode quantum memory. We then describe a series of experimental results using NV (as in nitrogen vacancy) center spins in diamond, which demonstrate its main building blocks: the transfer of arbitrary quantum states from a qubit into the spin ensemble, and the multi-mode retrieval of classical microwave pulses down to the single-photon level with a Hahn-echo like sequence. A reset of the spin memory is implemented in-between two successive sequences using optical repumping of the spins.     

3D ordered macro-/mesoporous Ni_xCo_(100-x) alloys as high-performance bifunctional electrocatalysts for overall water splitting

Electrochemical water splitting is a facile and effective route to generate pure hydrogen and oxygen.However,the sluggish kinetics of hydrogen evolution reaction(HER) and especially oxygen evolution reaction(OER) hinder the water splitting efficiency.Meanwhile,the high-cost of noble-metal catalysts limit their actual application.It is thus highly urgent to exploit an economical and earthabundant bifunctional HER and OER electrocatalyst to simplify procedure and reduce cost.Herein,we synthesize the three-dimensionally ordered macro-/mesoporous(3 DOM/m) Ni_xCo_(100-x) alloys with distinctive structure and large surface area via a dual-templating technique.Among them,the3 DOM/m Ni_(61)Co_(39) shows the lowest overpotentials of 121 mV and 241 mV at 10 mA/cm~2 for HER and OER,respectively.Furthermore,when employed for water splitting,the Ni_(61)Co_(39) only requires 1.60 V to approach 10 mA/cm2 and presents excellent stability.These encouraging performances of the Ni_(61)Co_(39)render it a promising bifunctional catalyst for overall water splitting.     

飞秒激光冲击AZ31B镁合金过程的数值模拟

采用有限元分析法对飞秒激光冲击AZ31B镁合金进行数值模拟,研究了激光冲击处理对镁合金变形过程的影响,分析了单脉冲激光冲击下材料内部的位移、动能、应力和应变的分布情况,得到了材料的瞬态速度和应变率变化过程.仿真结果表明,单脉冲飞秒激光冲击镁合金产生的塑性变形,可在材料表面形成微米级凹坑,中心点处最大位移为34μm,最大变形速度390m/s;在冲击初期,材料表面的应力和应变主要分布在冲击区域中心节点和边缘附近,并且得到镁合金的最大应力和最大应变率分别为955 MPa和1.8×106 s-1.研究结果能够为深入分析飞秒激光与镁合金作用时材料变形参量的变化规律提供数值理论依据.     

Formation of H3+ in Collisions of H2+ with H2 Studied in a Guided Ion Beam Instrument

In order to study collisions between ions and neutrals, a new Guided Ion Beam (GIB) apparatus, called NOVion, has been assembled and tested. The primary purpose of this instrument is to measure absolute cross sections at energies relevant for technical or inter- and circumstellar plasmas. New and improved results are presented for forming H₃⁺ in collisions of H₂⁺ with H₂. Between 0.1 eV and 2 eV, our measured effective cross sections are in good overall agreement with most previous measurements. However, at higher energies, our results do not show the steep decline, recommended in the standard literature. After critical evaluation of all experimental and theoretical data, a new analytical function is proposed, describing properly the dependence of the title reaction on the collision energy up to 10 eV.     

Polymerization in a magnetic field. X. Solvent effect in poly(methyl methacrylate) synthesis

The effect of a continuous external magnetic field on the free radical polymerization of methyl methacrylate was studied with respect to some properties of the solvents used in the reaction. The studies were performed through dilatometric technique in and out a magnetic field of 0.25 T. Ten different solvents were used to underline the dependence between the magnetic field presence, the reaction medium, and the development of the polymerization process. The intervened magnetokinetic effects are attributed to the changes in the multiplicity of the radical pairs owing to the magnetic field influence. There is an interdependence among the viscosity and molar polarization of the solvents and the magnetic field effect. © 1996 John Wiley & Sons, Inc.     

红外光谱技术对广东博罗横岭山商周时期墓地出土古玉器上蜡工艺的揭示及其意义

广东博罗横岭山商周时期墓地是广东省目前所发现的最重要的商周时期墓葬群,该墓地出土的玉器样品通过一系列的科学鉴定研究后发现,玉器的红外光谱在2 960 cm-1(相对较弱)、2 920和2 853 cm-1附近出现了2～3个明显的特征性吸收峰,结合对纯蜡样品、现代上蜡玉器样品的测试比较,认为博罗横岭山墓地出土玉器在加工过程中曾经经过上蜡处理,首次揭示出商周时期岭南先民掌握了在加工中利用蜡来增加玉器美观技术的事实。     

聚合物纳米孔隙增透膜制备工艺的研究

论述了聚合物纳米孔隙增透膜的制备工艺流程,分析了聚合物材料分子量、实验环境温度和湿度、溶剂挥发性等条件对纳米孔隙增透膜的影响。研究表明,聚合物材料分子量的增大、温度的降低、湿度的升高以及采用挥发性弱的溶剂都将导致增透膜孔隙尺寸的增大,孔隙越大其对光的散射损耗就会增大,所以增透膜的透过率就越低。通过大量的试验分析得出一组较理想的工艺参量:使用低分子量的聚合物材料(小于15 kg/mol),环境温度大于25℃、环境相对湿度小于30%,在采用低沸点的溶剂如四氢呋喃等措施下可有效降低增透膜散射损耗。     

脉冲压缩光栅光路调节新方法研究

介绍了一种简单而实用的大口径脉冲压缩光栅光路调节方法,有效解决了普通光路调节方法中轴向调节精度不高的问题。首先由全息透镜(光栅)成像公式出发,推导出了该光路调节的基本原理。并从光栅记录系统与光栅衍射波像差的关系,结合初级像差理论推导得出叠栅条纹像差为0.4786λ,大约是光栅衍射波像差(0.25λ)的两倍,利用此关系也可对光栅衍射波像差进行实时监测。从数值模拟结果可知,利用叠栅条纹法调节光路可将光栅波像差减至0.06λ,相应的轴向误差量为0.007 mm,可有效提高了轴向调节精度。     

Nd:GGG晶体荧光寿命的测试

针对Nd:GGG激光器,介绍了荧光寿命测试原理,设计了低频窄脉宽荧光寿命测试系统.该系统由光源、光路系统、驱动电路和探测系统等几部分组成.利用脉冲取样技术测试了Nd:GGG晶体的荧光寿命约为250μs左右.