Diagnosis, prescription, and prognosis of a bell-state filter by quantum process tomography

We apply the techniques of quantum process tomography to characterize errors and decoherence in a prototypical two-photon operation, a singlet-state filter. The quantum process tomography results indicate a large asymmetry in the process and also the required operation to correct for this asymmetry. We quantify residual errors and decoherence of the filtering operation after this modification.     

太赫兹自由电子激光波荡器的设计、测量与优化

波荡器电子轨迹中心偏移和磁场误差对CTFEL装置性能影响很大,通过前期设计和后期测量与优化将其限制在指标要求范围内。在前期设计中尽量避免引入全局性的系统误差：磁结构具有平面反对称结构,保证电子轨迹中心和波荡器磁轴重合;磁结构端部的特殊设计减弱了间隙对出口磁场二次积分的影响;机械系统的大梁和立柱具有良好的刚性,闭环控制系统保证了高的波荡器间隙控制精度,这些措施降低了间隙不一致引入的磁场误差。在后期测量与优化中削弱了磁场的残存全局系统误差和局部随机误差：利用磁场点测台测量了波荡器磁场的纵向和横向分布,通过调节标准单元组件位置对磁场进行了垫补和优化,优化后电子轨迹中心偏移、峰峰值误差、相位误差、好场区及其误差均满足指标要求。     

On initialization,error and flux conservation in the doubling method

Truncation errors and flux conservation errors in the doubling method are examined. The error properties of five different initial-layer approximations are compared as a function of initial-layer size, layer optical depth, single-scattering albedo, and phase function asymmetry parameter. The “diamond” initial-layer approximation is found to be orders of magnitude more accurate than the others for fixed initial-layer size, or of equivalent accuracy starting from a very much larger initial layer. The commonly used single-scattering initialization is shown to lead to serious flux conservation errors. Analytic error estimates, based upon a new derivation of the single-scattering initialization directly from doubling, are shown to be useful when the layer optical depth is on the order of 10 or less. Finally, questions of round-off error, calculation of an “exact” answer using Richardson extrapolation, and computational efficiency are all addressed briefly.     

Charged multiplicities in Z decays into u, d, and s Quarks

About 4.4 million hadronic decays of Z bosons, recorded by the OPAL detector at LEP at a centre-of-mass energy of around GeV, are used to determine the mean charged particle multiplicities for the three light quark flavours. Events from primary u, d, and s quarks are tagged by selecting characteristic particles which carry a large fraction of the beam energy. The charged particle multiplicities are measured in the hemispheres opposite to these particles. An unfolding procedure is applied to obtain these multiplicities for each primary light quark flavour. This yields where statistical and systematic errors are given. The results for and are almost fully statistically anti-correlated. Within the errors the result is consistent with the flavour independence of the strong interaction for the particle multiplicities in events from the light up, down, and strange quarks. Received: 5 October 2000 / Published online: 15 March 2001     

High order accurate, explicit, difference formulas for the classical wave equation

This article presents a simple and yet very novel approach to developing difference schemes for wave equations. The schemes that are developed are explicit in nature. The schemes are of such generality that one can transform from one difference scheme to another with only the slightest of computational effort. The schemes exhibit dispersive errors. The errors can be minimized, however, by increasing the order of truncation error. Numerical results are presented for two linear model equations with truncation error ranging up to O(h⁵). Numerical results are also presented for a system of shallow water equations. By choosing the appropriate a for a first order linear equation (a defines the geometry of an element) we may generate stable schemes for an arbitrary Courant number.     

Delays,inaccuracies and anticipation in microscopic traffic models

We generalize a wide class of time-continuous microscopic traffic models to include essential aspects of driver behaviour not captured by these models. Specifically, we consider (i) finite reaction times, (ii) estimation errors, (iii) looking several vehicles ahead (spatial anticipation), and (iv) temporal anticipation. The estimation errors are modelled as stochastic Wiener processes and lead to time-correlated fluctuations of the acceleration.We show that the destabilizing effects of reaction times and estimation errors can essentially be compensated for by spatial and temporal anticipation, that is, the combination of stabilizing and destabilizing effects results in the same qualitative macroscopic dynamics as that of the, respectively, underlying simple car-following model. In many cases, this justifies the use of simplified, physics-oriented models with a few parameters only. Although the qualitative dynamics is unchanged, multi-anticipation increase both spatial and temporal scales of stop-and-go waves and other complex patterns of congested traffic in agreement with real traffic data. Remarkably, the anticipation allows accident-free smooth driving in complex traffic situations even if reaction times exceed typical time headways.     

Induced-charge errors in charge-transfer measurement: Brush discharges between charged,insulating discs and earthed,conductive spheres

Charge-transfer measurements made with fast-response, unshielded probes will, in principle, underestimate charge-transfers because of induced-charge errors. It is, however, difficult to know when the degree of underestimation is significant or to allow for it quantitatively because information on the magnitude of these errors is fragmented. Consequently, when measurements are done for electrostatic hazard assessment, unsafe equipment could wrongly be classified as safe. To rectify this situation, and thus contribute to improving charge-transfer test methods in static electricity standards, we have systematically calculated induced-charge errors in brush discharges between insulating discs and earthed spheres. Errors are expressed as the charge-collection efficiency, which is the ratio of charge transfer in the external measurement circuit to charge transfer across the discharge gap. Key results are the worst-case efficiencies at the charge-transfer ignition-thresholds suggested for different classes of flammable material (60 nC, 30 nC and 10 nC for gas group IIa, IIb and IIc materials respectively). For 60 nC transfers and with our best estimate of post-discharge conditions on the disc surface, the worst-case charge-collection efficiency is 0.56, which indicates the error-allowance needed for safe assessment. For 30 nC or 10 nC transfers, the charge-collection efficiency is both smaller (～0.2), and considerably more sensitive to gap geometry. Consequently, it is not recommended to use charge-transfer measurements with fast, unshielded probes to assess electrostatic hazards for gas group IIb or IIc materials.     

Equivalent Model, Error Analysis, and Design Steps of AGC Loop for MM-Wave Receiver

Automatic Gain Controlled (AGC) Loops are used in MM-Wave receiver in wide-ranging. In this paper, the equivalent model and loop equation of AGC Loop are built, the loop errors are analyzed and then the design steps of AGC Loop are given out.     

Forecasting Earth's magnetopause, magnetosheath, and bow shock

The magnetopause and bow shock are two of the most important discontinuities in near Earth space, separating three distinct plasma regimes: the solar wind, magnetosheath, and the magnetosphere. Both discontinuities are sensitive to the solar wind conditions. They change their shape and location in space in response to upstream solar wind variations. Prediction of the location of a satellite relative to these two boundaries helps satellite operators to be prepared for major changes in plasma condition. The physical conditions near the magnetopause are useful information for magnetospheric models. Over the past decades, our observational knowledge and physical understanding of these regions have been advanced significantly. We have developed the capability of prediction. The location of the magnetopause and its dependence on the upstream conditions can be relatively accurately predicted. Prediction models have been tested extensively. The success rate is extremely high and the false-alarm rate is relatively low. A magnetosheath prediction model has been developed and tested. Some of the magnetosheath quantities can often be predicted fairly accurately. Others may have slightly larger errors. Further tests and scientific investigations of the causes of these errors are under way. Our ability to predict the location of the bow shock is very limited. More research is needed     

20 MeV以下65Cu(n,p)65Ni 反应截面及其协方差数据的评价

为满足核工程对核数据的需求,对20 MeV以下65Cu(n, p)65Ni 反应截面的实验数据进行了分析和评价,包括实验数据的收集、修正、选取、归一、误差调整和数据处理,在分析实验误差特别是关联误差的基础上构造了每家数据的协方差矩阵,最后利用样条拟合程序SPCC给出了评价截面数据和实验数据的协方差矩阵。评价不仅考虑了实验数据的误差,还考虑了数据间的相关性。To meet the needs for nuclear data engineering, the experimental data of the 65Cu(n, p)65Ni cross section below 20 MeV were analyzed and evaluated.The evaluation procedure includes the experimental data collection, correction, selection, normalization, error adjustment and data processing, especially the covariance matrix for each experimental data is constructed with the information on experimental errors and correlation errors. The evaluation cross section data and the corresponding covariance matrices were given using the spline fitting procedure SPCC. The evaluation work was done with the consideration of not only the experimental errors but also the correlation of data.     

The photonical, pure grid method

The paper presents an introduction on the pure grid method for deformation measurements in experimental mechanics. The pure grid method involves that the grid images are processed separately, and subsequently the results of these separate processings are substrated from each other in order to obtain a quantified deformation indication.The recording and processing of the grid images are currently performed photonically by means of digital image measurement systems. The basic data processing relations and set-ups of four different applicabilities of the photonical, pure grid method are presented in this paper. The applicabilities are discussed. Strains can be measured with errors smaller than 200 micro strain and displacements with errors smaller than of the diameter of the object as visible in the grid image. These figures can be improved substantially by future application of high resolving-power CCD cameras. Two examples are shown. The paper also contains an extensive bibliography for further explorations.     

声矢量阵阵元位置及幅相误差有源校正算法*

针对声矢量阵幅相误差及阵元位置误差校正问题,基于特征分解法,提出一种简单实用的有源校正算法。该方法需要合作信源的至少3个方位信息,根据声矢量阵的通道特征,利用特征分解法构造矩阵方程组,通过矩阵运算得到声矢量阵阵元位置和幅相误差参数,从而实现对声矢量阵的校正。大量计算机仿真表明该校正算法具有良好的声矢量阵阵列误差参数估计性能。     

CCD摄像机的误差及其检校

在利用面阵CCD摄像机进行摄影测量和检测的系统中,CCD摄像机所产生的误差是系统的主要误差,这种误差是在图像输入的过程中产生的。CCD摄像机的误差一般分光学误差、机械误差和电学误差。在摄像机光学镜头与CCD器件质量比较好的情况下,其主要表现是电学误差,重点讨论电学误差及其检测。     

The accuracies of photometric, polarimetric and ellipsometric methods for the optical constants of thin films

The inherent accuracies of various techniques for determining the optical constants of thin films have been assessed by computing the errors produced in n and k by known experimental errors in the optical functions being measured. The results are presented as arrays of error parallelograms in the n–k plane covering d/λ from 0.001 to 0.20 and θ from 5° to 85°.The largest regions of accuracy, in the form of annular quadrants, were obtained using the mixed photometric and polarimetric functions at small angles of incidence. Ellipsometry gives similar results at large angles of incidence but for photometry and for polarimetry the accurate regions were in the form of two lobes.The effects of errors in x and θ were also considered.     

Quantum: Einstein,Bohr and the Great Debate About the Nature of Reality,by Manjit Kumar

The history of absolute measurements of gravity is mentioned and the reasons for making absolute measurements are indicated. The principles and main advantages and difficulties of the main method—reversible pendulum, free fall, symmetrical free motion—are discussed and examples of each method are described. Problems of comparison of different determinations and of estimating systematic errors are considered.     

Analysis and correction of linear optics errors,and operational improvements in the Indus-2 storage ring

Estimation and correction of the optics errors in an operational storage ring is always vital to achieve the design performance. To achieve this task, the most suitable and widely used technique, called linear optics from closed orbit(LOCO) is used in almost all storage ring based synchrotron radiation sources. In this technique, based on the response matrix fit, errors in the quadrupole strengths, beam position monitor(BPM) gains, orbit corrector calibration factors etc. can be obtained. For correction of the optics, suitable changes in the quadrupole strengths can be applied through the driving currents of the quadrupole power supplies to achieve the desired optics. The LOCO code has been used at the Indus-2 storage ring for the first time. The estimation of linear beam optics errors and their correction to minimize the distortion of linear beam dynamical parameters by using the installed number of quadrupole power supplies is discussed. After the optics correction, the performance of the storage ring is improved in terms of better beam injection/accumulation, reduced beam loss during energy ramping, and improvement in beam lifetime. It is also useful in controlling the leakage in the orbit bump required for machine studies or for commissioning of new beamlines.     

Numerical Inversion of the Abel Integral Function,Using Least-Squares Splines

In the Abel inversion of a function whose values are determined experimentally on a discrete set of points, random errors are amplified considerably. This paper presents a procedure to smooth the data before inversion, and thus keep the error amplification under control.     

Analysis of Phase Measurement Errors in Electro-Optic Holography

This paper presents the results of an error analysis in electro-optics holography. These errors include phase measurement errors due to the linear phase shifter errors in static electro-optic holography, and phase measurement errors due to the errors in the vibrating bias amplitude and phase in dynamic electro-optic holography. Through the error analysis, we found that the phase shifting errors in static electro-optic holography are twice as large as those in the conventional 4-bucket phase shifting algorithm, and the phase shifting errors in dynamic electro-optic holography are similar to those in the 4-bucket phase shifting algorithm.