Tl2Ba2CaCu2O8薄膜直流超导量子干涉器的噪声特性

本给出了Ｔｌ２Ｂａ２ＣａＣｕ２Ｏ８薄膜双晶结直流超导量子干涉器噪声测量的实验结果。与至今最好的ＹＢＣＯ薄膜器件噪声测量结果相比，铊器件１／ｆ特性低频噪声的起始频率要低二个数量级。本还详细介绍了器件在闭环工作模式时，其噪声频谱的测量方法。     

在一个磁通量子内dc Josephson电流的阶梯效应(Ⅰ) 双结SQUID

如果将由两个相同的Josephson结组成的双结SQUID放置于Q值足够高的谐振腔内,当其Josephson频率ω=2eV_0/h与谐振腔的本征频率ω_r发生谐振时,腔内就被激起一个驻波电磁场,这个场对两个结的反馈作用,将导致双结SQUID的dc Josephson电流在一个磁通量子内随磁场产生多次阶梯效应。 理论给出两个结的Josephson电流产生一系列新的干涉作用:如果两个结分别位于反馈场的波峰,则阶跃电流加强;如果其中一个位于波谷,则使SQUID的干涉图形改变π/2位相,且两个结电流产生相干性减小;如果一个在波峰一个在波节,则SQUID退化到单结;如果两个结都在波节,则不出现n≠0的阶梯。     

蘇聯的电介質和半导体研究工作

一.电介质 在本世纪的初年,电机工程上所用的全部材料可以分成两类:导体和绝缘体或电介质。大家知道,并不是所有的电介质都是完全的绝缘体;在电介质中亦有电流流过;这样的电流已在十九世纪末年为法国物理学家Fousserau和JacquesCurie研究过。二十世纪初年,电介质的研究在德国和俄国得到很大的发展。电流在电介质中所显现的特殊性使人们认为这样的电流仅仅是电介质的反常(表徵弹性反常和磁性反常的落后、滞后等现象)。     

在一个磁通量子内dc Josephson电流的阶梯效应(Ⅱ)——大尺寸Josephson结

大尺寸的Josephson结放置于Q值足够高的谐振腔中,当其Josephson频率ω=2cV₀/h激励起腔的第r个本征模谐振时,这个振荡将反馈辐照结,必须考虑反馈场本征模的空间部分在结上是不同的。理论上得到了和文献[2]不同的结果,给出了阶跃电流随磁场的变化,分析了腔的反馈场本征模和Josephson结的辐射电磁波空间匹配的条件,解释了为什么大尺寸的Josephson结不存在周期小于φ₀的阶梯效应的物理原因。 关键词：     

La1/8Ca7/8MnO3/Sr0.95Nb0.05TiO3异质结的整流特性和磁输运性质

在5%Nb掺杂的SrTiO3衬底上用磁控溅射法外延生长了La1/aCa7/aMnO3薄膜形成异质结,该异质结有类似于传统P-n结的整流特性.磁场下扩散电压减小,当温度低于130 K以下,扩散电压的减小非常明显.这和在此温度以下,La1/8Ca7/aMnO3出现自旋倾斜态密切相关.我们计算出异质结的结电阻和磁致电阻(MR),在不同大小的正负偏压,不同磁场下,都得到负的MR值.我们给出界面附近的La1/8Ca7/8MnO3的能带结构并分析了外加磁场对洪德耦合,Jahn-Teller畸变等机制的作用,来解释该异质结的磁输运行为.结果有助于了解高Ca掺杂锰氧化物异质结的性质.     

量子纠缠态的普适远程克隆

提出一种任意两粒子纠缠态1→2普适远程克隆方案. 此方案仅需一个特殊的四粒子纠缠态作为量子信道, 就可使处于空间不同位置的两个接收者分别以5/6的保真度得到任意输入态的近似拷贝, 该保真度远高于已有方案中的保真度. 将方案推广到任意两粒子纠缠态1→N(N>2)普适远程克隆的情况, 可使处于不同地点的N个接收者分别以(2N+1)/(3N)的保真度得到输入态的近似拷贝. 另外, 提出一种以上述单个特殊四粒子纠缠态作为量子信道, 在多目标量子比特受控非门和 关键词： 量子纠缠态 普适远程克隆 保真度     

A Scheme for Generating Entangled Squeezed States Based on Cavity QED

We propose a scheme for generating entangled squeezed vacuum states of electromagnetical fields. The scheme is based on cavity QED. In this scheme, an atom interacts, successively, with a classical field, two quantum cavity fields, and another classical field. By detecting the final states of the atom, the two quantum cavity fields will be projected to an entangled state.     

Efficiency Enhancement of Dye-Sensitized Solar Cells： Using Salt CuI as an Additive in an Ionic Liquid

Energy conversion efficiency of the dye-sensitized solar cell is improved from 3.5% to 4.5% by adding a small amount of CuI into an ionic liquid electrolyte. It is found that other copper-I salts, for example, CuBr, have the same effect for the dye-sensitized solar cell. Experimental results show that no Cu^2＋ ions exist in this electrolyte. It is suggested that this improvement is caused by the adsorption of Cu^＋ onto the TiO2 porous film.     

Effect of Reactor Pressure on Qualities of GaN Layers Grown by Hydride Vapour Phase Epitaxy

The influence of reactor pressure on GaN layers grown by hydride vapour phase epitaxy （HVPE） is investigated. By decreasing the reactor pressure from0. 7 to 0.5 mm, the GaN layer growth mode changes from the island-like one to the step flow. The improvements in structural and optical properties and surface morphology of GaN layers are observed in the step flow growth mode. The results clearly indicate that the reactor pressure, similarly to the growth temperature, is One of the important parameters to influence the qualities of GaN epilayers grown by HVPE, due to the change of growth mode.     

Analytic solutions for degenerate Raman-coupled model

The Raman-coupled interaction between an atom and a single mode of a cavity field is studied. For the cases in which a light field is initially in a coherent state and in a thermal state separately, we have derived the analytic expressions for the time evolutions of atomic population difference W, modulus B of the Bloch vector, and entropy E. We find that the time evolutions of these quantities are periodic with a period of π. The maxima of W and B appear at the scaled interaction time points τ- = kπ（k = 0, 1, 2,...）. At these time points, E = 0, which shows that the atom and the field are not entangled. Between these time points, E ≠ 0, which means that the atom and the field are entangled. When the field is initially in a coherent state, near the maxima, the envelope of W is a Gaussian function with a variance of 1/（4n^-）（n^- is the mean number of photons）. Under the envelope, W oscillates at a frequency of n^-/π. When the field is initially in a thermal state, near the maxima, W is a Lorentz function with a width of 1/n^-.