Quantum memories and error correction

Quantum states are inherently fragile, making their storage a major concern for many practical applications and experimental tests of quantum mechanics. The field of quantum memories is concerned with how this storage may be achieved, covering everything from the physical systems best suited to the task to the abstract methods that may be used to increase performance. This review concerns itself with the latter, giving an overview of error correction and self-correction, and how they may be used to achieve fault-tolerant quantum computation. The planar code is presented as a concrete example, both as a quantum memory and as a framework for quantum computation.     

Depletion-enhanced body-isolation (DEBI) array on SOI for highly scalable and reliable NAND flash memories

A novel array architecture [depletion-enhanced body-isolation (DEBI)] has been proposed for NAND-type flash memories, and its memory characteristics are investigated in detail by device simulations. Having the shallow junctions on the thin active area, the proposed array architecture achieves high device performances with a fully depleted silicon-on-insulator (FDSOI) structure and enables stable erase operation without any problems based on an SOI structure. In particular, during the program operation, the DEBI architecture exhibited excellent self-boost efficiency originating from the isolated body. This can reduce the program disturbance effectively and can lower the V/sub pass/ voltages.     

Evaluation of multilevel memories

Proposed memory hierarchy technologies and configurations are usually evaluated by repeated running of "typical" jobs through simulated hierarchies while various parameters are adjusted. Simulation is too slow to be a tool for selecting among the choices in 1) technologies to be included, 2) implementation of each technology, and 3) management of data flow in the hierarchy. Four current hardware-managed hierarchies are described in a manner which parameterizes their design. The evaluation process is described in terms of address traces, hit ratios, and system cost performance. Stack processing is then described as a replacement for simulation that obtains hit-ratio data 1000 times faster than before. Finally, an example is given to illustrate how to select between two competing technologies, how to design the best hierarchy, and how to determine the information flow which optimizes the total cost performance of the system.     

在线色差检测的误差修正方案设计

基于色度学理论并结合实际颜色工业的生产过程,设计了准双光路光电积分型颜色测量系统并用于工业颜色差异的在线检测.基于在线色差检测过程中误差源的详细分析,提出了修正颜色传感器光谱特性、照明光源波动以及高频、低频环境噪声等各种因素造成的色差在线检测误差的方案,并通过工业应用的比对实验表明,误差修正后的实际色差变化曲线相对平滑,信噪比显著提高,完全能够满足实际色差控制的需要,证明了设计方法的有效性,为实现高精度的在线颜色测试和品质控制奠定了基础.     

Interleaving and error correction in volume holographic memory systems

We study the use of error-correction coding (ECC) and two-dimensional interleaving for volume holographic memory (VHM) systems suffering from both random and systematic errors. The bit-error rate (BER) is used as the data-fidelity measure and as a design metric for optical 4f systems. The correlated error patterns arising from both lens aberrations and misalignment errors are analyzed, and we discuss the information theoretic storage capacity of VHM in the presence of such correlated error patterns. The performance of interleaving and ECC is analyzed from both BER and storage-capacity perspectives. Magnification, rotation, tilt, and defocus errors are also studied, and an experimental demonstration that combines ECC with two-dimensional interleaving is included.     

Iterative soft-minimum mean-square error equalization for digital nonlinear page-oriented memories

Digital page-oriented volume holographic memory (POVHM) is a promising candidate for next-generation ultrahigh capacity optical data storage technology. As the capacity of the POVHMs increases, the bit error rate performance of the system is degraded due to increased interpixel interference (IPI) and noise. To improve the system performance under these adverse effects and to increase the capacity, joint iterative soft equalization-detection and error correction decoding might be attractive. To address that, by considering the nonlinearity inherent in the channel, an iterative soft equalization method that is optimized in the minimum mean-square error (MMSE) sense, called the iterative soft-MMSE (ISMMSE) equalization, is devised. The performance of the ISMMSE is evaluated by use of numerical experiments under different amounts of IPI and optical noise. Simulation results suggest that the ISMMSE is a good candidate for an ultrahigh capacity POVHM, which employs joint iterative equalization-detection and decoding.     

基于 NAND Flash 的嵌入式文件系统设计

主要介绍了针对 NAND Flash 型存储器设计的嵌入式文件系统. 其硬件平台是为了顺应多功能、大容量集成化存储的需求而开发的基于 ADSP-BF532 芯片与 NAND Flash 结合的高性能嵌入式存储系统. 此存储系统采用了多片并行流水的存储模式,开发出独特有效的闪存管理技术与改良的文件系统,通过设置访问权限实现多用户管理,使得处理器、存储器以及文件管理层软件的多方优势得以充分发挥.     

Electrical characteristics of nanoscale NAND silicon-oxide-nitride-oxide-silicon flash memory devices fabricated on SOI substrates

NAND silicon-oxide-nitride-oxide-silicon (SONOS) flash memory devices with double gates fabricated on silicon-on-insulator (SOI) substrates were proposed. The current-voltage characteristics related to the programming operation of the designed nanoscale NAND SONOS flash memory devices on a SOI substrate and on the conventional bulk-Si substrate were simulated and compared in order to investigate device characteristics of the scaled-down memory devices. The simulation results showed that the short channel effect and the subthreshod leakage current for the memory device with a large spacer length were lower than that of the memory device with a small spacer length due to increase of the effective channel length. The device performance of the memory device utilizing the SOI substrate exhibited a smaller subthreshold swing and a larger drain current level in comparison with those on the bulk-Si substrate. These improved electrical characteristices for the SOI devices could be explained by comparing the electric field distribution in a channel region for both devices.     

Combined error correction techniques for quantum computing architectures

Abstract

Proposals for quantum computing devices are many and varied. They each have unique noise processes that make none of them fully reliable at this time. There are several error correction/avoidance techniques which are valuable for reducing or eliminating errors, but not one, alone, will serve as a panacea. One must therefore take advantage of the strength of each of these techniques so that we may extend the coherence times of the quantum systems and create more reliable computing devices. To this end we give a general strategy for using dynamical decoupling operations on encoded subspaces. These encodings may be of any form; of particular importance are decoherence-free subspaces and quantum error correction codes. We then give means for empirically determining an appropriate set of dynamical decoupling operations for a given experiment. Using these techniques, we then propose a comprehensive encoding solution to many of the problems of quantum computing proposals which use exchange-type interactions. This uses a decoherence-free subspace and an efficient set of dynamical decoupling operations. It also addresses the problem of controllability in solid-state quantum dot devices.     

An error correction technique for scan conversion-based transientdigitizers

A statistical technique for the error correction of scan conversion-based transient digitizers is presented. The technique is based on the identification of the error model and on the assessment of the related correction feasibility. The identification of the error model is carried out for the charge distribution on each column of the target diode matrix of the scan digitizer through a suitable experimental procedure. The feasibility of the error correction is assessed on the basis of the statistical significance of the model identification by means of a decision-making procedure. A suitable index is utilized to verify the likelihood of carrying out a significant correction. Furthermore, for scan digitizers having a reference offset generator, a self-calibrating function based on the proposed technique is suggested. Finally, experimental results of the technique application to an actual scan conversion-based transient digitizer showing a significant error reduction are discussed     

Dynamic error correction of a digitizer for time-domain metrology

A method for numerical correction of distortion in a digitizer used for metrology applications is described. Investigation of the digitizer's error behavior in the phase plane leads to the development of an analytic error model that describes the digitizer's distortion behavior. Of particular significance is the model's ability to describe nonlinear error in the fundamental spectral component manifested as amplitude and frequency-dependent gain and phase error. When fitted only to the harmonic distortion content of the digitizer's output data, the model generates an amount of fundamental that correctly accounts for the error in the digitizer's gain that is not due to linear system response. The model is therefore able to improve not just the total harmonic distortion (THD) performance of the digitizer but its ac root mean square measurement accuracy as well. At 1 MHz, the model linearizes the digitizer to 70 /spl mu/V/V over a range of 1 to 8 V and reduces harmonic distortion by >20 dB. It is believed that this is the first time that results of this nature have been reported in the literature.     

Mueller matrix error correction for a fringe-free interferometry system

We present an automated surface profiling system based on a shearing interferometer, in which precise measurement of the polarization states eliminates fringe ambiguity. A full error correction based on Mueller matrices allows comparatively inaccurate but rapidly switchable liquid-crystal wave plates to be used, enabling unambiguous profile information to be obtained in real time.     

Automated system of error correction for universal multirange reference instruments

Translated from Izmeritel'naya Tekhnika, No. 11, pp. 19–20, November, 1989.     

Elf: computer automation and error correction for a microwavenetwork analyzer

A microwave measurement system has been developed that combines a personal computer (PC) and an conventional vector network analyzer to yield a full complex-error-corrected automatic network analyzer. The system consists of a Hewlett-Packard HP 8410C network analyzer, an HP 8350B sweep oscillator, and an IBM PC. A program called Elf runs on the PC, performing calibration and measurement algorithms and providing a flexible, menu-oriented user interface. The system, when calibrated, achieves a worst-case measurement error vector of magnitude ⩽0.02 for transmission and reflection coefficient measurements over the 2-12.4-GHz frequency range and has a measurement speed of three frequency points/s. Elf provides an inexpensive method for upgrading the HP 8410 to achieve the high accuracy of an automatic network analyzer     

Ion beam machining error control and correction for small scale optics

Ion beam figuring (IBF) technology for small scale optical components is discussed. Since the small removal function can be obtained in IBF, it makes computer-controlled optical surfacing technology possible to machine precision centimeter- or millimeter-scale optical components deterministically. Using a small ion beam to machine small optical components, there are some key problems, such as small ion beam positioning on the optical surface, material removal rate, ion beam scanning pitch control on the optical surface, and so on, that must be seriously considered. The main reasons for the problems are that it is more sensitive to the above problems than a big ion beam because of its small beam diameter and lower material ratio. In this paper, we discuss these problems and their influences in machining small optical components in detail. Based on the identification-compensation principle, an iterative machining compensation method is deduced for correcting the positioning error of an ion beam with the material removal rate estimated by a selected optimal scanning pitch. Experiments on ?10?mm Zerodur planar and spherical samples are made, and the final surface errors are both smaller than λ/100 measured by a Zygo GPI interferometer.     

猫眼光学误差的测量与修正

介绍了猫眼光学误差对激光跟踪三维坐标测量系统的影响及猫眼光学误差的主要来源,设计了一种猫眼光学误差的测量原理并构建了相应的测量装置,论述了测量数据处理方法以及在进行激光跟踪三维坐标测量时对猫眼光学误差进行修正的方法.在数据处理过程中,使用了非线性拟合算法来消除半球偏心和安装偏心对测量结果的影响,使用了二维插值算法来获取猫眼在任意入射方位角处的光学误差值.使用所构建的测量装置对Leica公司生产的CER75猫眼的光学误差进行了实际测量并对测量数据进行了处理.实验结果表明,被测猫眼在其接收角范围内的最大光学误差约为4μm.     

Quantum correlations,local interactions and error correction

Abstract

We consider the effects of local interactions upon quantum mechanically entangled systems. In particular we demonstrate that non-local correlations cannot increase through local operations on any of the subsystems, but that through the use of quantum error correction methods, correlations can be maintained. We provide two mathematical proofs that local general measurements cannot increase correlations, and also derive general conditions for quantum error correcting codes. Using these we show that local quantum error correction can preserve non-local features of entangled quantum systems. We also demonstrate these results by use of specific examples employing correlated optical cavities interacting locally with resonant atoms. By way of counter example, we also describe a mechanism by which correlations can be increased, which demonstrates the need for non-local interactions.     

片上波动影响下的Mesh结构时钟系统的性能分析方法

考虑到片上波动对Mesh结构时钟系统的影响,提出了一种基于统计理论的时钟系统性能分析方法。该方法的核心思想是在真实的解析函数难以求解的情况下,采用统计分析方法对该函数进行拟合。从两方面着手研究:如何拟合时钟偏差的概率分布;如何拟合前驱动层时钟路径的时延对时钟偏差的影响。实验证明,时钟偏差的概率分布可用正态分布拟合,而前驱动层时钟路径的时延与时钟偏差的关系可采用多元线性回归模型进行拟合。因此,这套拟合方法使设计人员能够通过正态分布的概率分布函数评估不确定性约束是否合理;在设计后期,根据多元线性回归模型调节优化前驱动层,提高时钟系统的性能。