Information-Efficient,Off-Center Sampling Results in Improved Precision in 3D Single-Particle Tracking Microscopy

In this work, we present a 3D single-particle tracking system that can apply tailored sampling patterns to selectively extract photons that yield the most information for particle localization. We demonstrate that off-center sampling at locations predicted by Fisher information utilizes photons most efficiently. When performing localization in a single dimension, optimized off-center sampling patterns gave doubled precision compared to uniform sampling. A ~20% increase in precision compared to uniform sampling can be achieved when a similar off-center pattern is used in 3D localization. Here, we systematically investigated the photon efficiency of different emission patterns in a diffraction-limited system and achieved higher precision than uniform sampling. The ability to maximize information from the limited number of photons demonstrated here is critical for particle tracking applications in biological samples, where photons may be limited.     

颗粒溶液颗粒尺寸及浓度的差分偏振弹性散射光谱在线分析方法

偏振弹性散射光谱技术的基本原理为在偏振光入射条件下,根据出射光的偏振特性不同可以筛选出浅表层组织的单次散射光信息和深层组织的漫散射光信息。该研究的创新点在于将这种方法应用于颗粒溶液检测,目的是在颗粒溶液原始状态下实现对颗粒尺寸及浓度的同时检测。设计了一个共轴笼式光学系统,测量了聚苯乙烯微球颗粒溶液某一角度的背向散射信号,通过控制入射端和收集端偏振片的偏振方向获得了颗粒溶液的偏振平行光谱与偏振垂直光谱,两者之差即偏振差分光谱对应颗粒的单次散射信息,将该单次散射信息与Mie散射数据库进行比对获得颗粒的尺寸,然后在颗粒尺寸作为已知的条件下进一步分析偏振垂直光谱,将该垂直光谱对应的颗粒溶液的漫散射信息代入光漫散射下的近似表达式拟合得到颗粒的浓度信息。将实验结果与样品提供值进行了比对,并进一步分析了在获取颗粒数浓度时,颗粒直径的方差分布对结果的影响,最终验证了该实验方法的可行性。该方法的潜在应用包括对标准颗粒制造厂商的产品在线检测以及对牛奶制品中脂肪和蛋白质的浓度检测研究。     

量子点接触对单电子量子态的量子测量

研究了用介观量子点接触(QPC)对单电子两态和多态系统的量子测量问题.发现,在任意测量电压下,该测量问题不能用标准的Lindblad量子主方程描述.考虑了测量仪器和被测系统之间的能量交换对细致平衡关系的影响,对该问题提供了一个恰当的理论描述,并对未来的固态量子测量和量子反馈控制可能产生一定影响. 关键词： 量子测量 量子比特 细致平衡 退局域化     

基于自适应共振神经网络的单粒子激光电离质谱数据分析

气溶胶激光飞行时间质谱仪(ALUOFMS)可以在线地对气溶胶单粒子进行物理和化学特性分析,利用双束连续激光对单个粒子的空气动力学粒径进行测量,并通过飞行时间完成单粒子化学成分的检测。该仪器在运行过程中将产生海量的实验数据,对这些数据快速、自动处理并提取有价值的信息是整机系统的关键之一。文章介绍了基于神经网络的自适应共振算法(ART-2a)在随机混和的氯化钠、氯化钙、邻苯二甲酸二正辛酯(DOP)和2,5二羟基苯甲酸(DHB)气溶胶单粒子聚类分析中的成功运用。同以往的质谱分析方法相比,ART-2a可以实现对任意多和任意复杂的输入模式进行自组织,自适应和自稳定的快速识别,更有利于质谱数据的分析。实验结果表明,当警戒值为0.40,学习速率为0.05以及迭代次数为6时,ART-2a可以成功地对这四种物质进行分类,同时得到4类物质的聚类中心,每类的聚类中心都能很好的代表该类物质的特征。     

Compositional analysis of multi-element magnetic nanoparticles with a combined NMR and TEM approach

The increasing interest in nanoscale materials goes hand in hand with the challenge to reliably characterize the chemical compositions and structural features of nanosized objects in order to relate those to their physical properties. Despite efforts, the analysis of the chemical composition of individual multi-element nanoparticles remains challenging—from the technical point of view as well as from the point of view of measurement statistics. Here, we demonstrate that zero-field solid-state nuclear magnetic resonance (NMR) complements local, single particle transmission electron microscopy (TEM) studies with information on a large assembly of chemically complex nanoparticles. The combination of both experimental techniques gives information on the local composition and structure and provides an excellent measurement statistic through the corresponding NMR ensemble measurement. This analytical approach is applicable to many kinds of magnetic materials and therefore may prove very versatile in the future research of particulate magnetic nanomaterials.     

Thermodynamic model for feedback control of systems with uncertain macroscopic states

Thermodynamics of feedback control processes, including the minimum work consumption of measurement, work extraction, and erasure processes of thermodynamic small systems have been investigated by researchers. We take systems with uncertain macroscopic states as the study object and study the feedback control processes of nonequilibrium macroscopic systems considering both the information entropy of microscopic states and macroscopic states. First we consider a system set that consists of systems with several macroscopic states and discuss the relations among the average information entropy of the system set, the thermodynamic entropy of the systems and the information entropy of macroscopic states of the systems. Then, we derive the expression of the average maximum net work obtained through feedback control, which relates to the free energy of the systems and the minimum work consumption of the measurement and erasure processes.     

Monte Carlo calculation of the mean work required to drive a bistable system

The mean work required to drive a bistable system from one equilibrium state to another is calculated by using a Langevin simulation combined with Monte Carlo sampling. The resulting work depends not only on the proposal form but also on the temperature, because the particle subjected to thermal fluctuation passes over the barrier during a finite time. This shows that the mean work of a periodic signal done on a particle in a double-well potential is a non-monotonic function of the temperature when the energetic barrier is encountered. By applying this to information erasure in a Brownian computer, it is discovered that the work dissipated into the environment for 1-bit information erasure from two states to a single state can be minimized at a finite temperature.     

Unitary models of single detector triggering and local position measurements

Recent work by Wan and McLean has shown that all quantum measurements may be reduced to local position measurements. Using an array of particle detectors as the measuring apparatus we show how a model employing superselection rules and unitary evolution leads to a single detector triggering in each act of measurement. We also present an explicit model of particle detection as a unitary ionization process producing a single ion in the detector, subsequent amplification of which to the visible can be described adequately in classical terms.     

A chemometric method to identify enzymatic reactions leading to the transition from glycolytic oscillations to waves

In the present work we demonstrate that FTIR-spectroscopy is a powerful tool for the time resolved and noninvasive measurement of multi-substrate/product interactions in complex metabolic networks as exemplified by the oscillating glycolysis in a yeast extract. Based on a spectral library constructed from the pure glycolytic intermediates, chemometric analysis of the complex spectra allowed us the identification of many of these intermediates. Singular value decomposition and multiple level wavelet decomposition were used to separate drifting substances from oscillating ones. This enabled us to identify slow and fast variables of glycolytic oscillations. Most importantly, we can attribute a qualitative change in the positive feedback regulation of the autocatalytic reaction to the transition from homogeneous oscillations to travelling waves. During the oscillatory phase the enzyme phosphofructokinase is mainly activated by its own product ADP, whereas the transition to waves is accompanied with a shift of the positive feedback from ADP to AMP. This indicates that the overall energetic state of the yeast extract determines the transition between spatially homogeneous oscillations and travelling waves.     

New technique to measure particle size using electrostatic sensor

A new technique is proposed to measure the particle mean size using an electrostatic sensor in frequency domain. This paper starts with a finite-element modeling simulator to model the induced electric charge of a ring electrode and to find the electrode sensitivity. The mathematical modeling was used to extract particle size information from the simulated signal in frequency domain. The method is applied in an experimental test where a low-noise signal conditioning was designed with a ring electrode as the electrostatic sensor. The method can be used to establish a cost effective size measurement system using electrostatic sensor.     

Feedback control of quantum system

Feedback is a significant strategy for the control of quantum system. Information acquisition is the greatest difficulty in quantum feedback applications. After discussing several basic methods for information acquisition, we review three kinds of quantum feedback control strategies: quantum feedback control with measurement, coherent quantum feedback, and quantum feedback control based on cloning and recognition. The first feedback strategy can effectively acquire information, but it destroys the coherence in feedback loop. On the contrary, coherent quantum feedback does not destroy the coherence, but the capability of information acquisition is limited. However, the third feedback scheme gives a compromise between information acquisition and measurement disturbance.     

Authenticable Quantum Scheme for Secret Sharing Based on Local Distinguishability

The main defects of the existing quantum secret sharing schemes are as follows: (1) The identity of the secret sender cannot be confirmed. Receivers of shared secret information may be vulnerable to Trojan attacks; (2) If a malicious attacker Eve impersonates the identity of the receiver, she can finally obtain all the information of the secret that Alice shared; (3) In the process of secret recovery, it is necessary to transmit qubits among all participants involved in secret recovery. Sometimes, the same particle needs to be operated on by all participants to achieve secret sharing, which increases the possibility of eavesdropping and also increases the probability of errors. In this work, we proposed a quantum secret sharing scheme with authentication, the receiver performs corresponding operations on qubits of Greenberger-Horne-Zeilinger(GHZ) state based on the key string calculated by the shared identity number and random Error Correction Code(ECC), the secret sender can calculate the corresponding measurement basis(MB) through the information she has, and then inform the measurement party. This process realizes the mutual authentication between the sender and the receiver. It can protect against identity impersonation attacks, through the ECC verification, it also can resist intercept-resend attacks.

     

Model-independent analysis of density-matrix element measurements in multiparticle reactions

We present a general study of polarization measurement in multiparticle production processes, including a definition of experimentally observable quantities, the splitting into natural- and unnatural parity exchanges and a study of their relative phase, and information concerning the quantum numbers of a packet of particles. When only one single particle is detected in the final state (inclusive reactions for instance) we prove that the usual formalism for two-body reactions is applicable. Very interesting new information on multi-particle production can be reached when it can be asserted that another particle has been emitted above or below a given plane, parallel or perpendicular to the scattering plane.     

Precise, real-time, every-single-shot, carrier-envelope phase measurement of ultrashort laser pulses

In this Letter we demonstrate a method for real-time determination of the carrier-envelope phase of each and every single ultrashort laser pulse at kilohertz repetition rates. The technique expands upon the recent work of Wittmann and incorporates a stereographic above-threshold laser-induced ionization measurement and electronics optimized to produce a signal corresponding to the carrier-envelope phase within microseconds of the laser interaction, thereby facilitating data-tagging and feedback applications. We achieve a precision of 113 mrad (6.5°) over the entire 2π range.     

Quantum simulations of a particle in one-dimensional potentials using NMR

A quantum computer made up of a controllable set of quantum particles has the potential to efficiently simulate other quantum systems. In this work we studied quantum simulations of single particle Shrödinger equation for certain one-dimensional potentials. Using a five-qubit NMR system, we achieve space discretization with four qubits, and the other qubit is used for preparation of initial states as well as measurement of spatial probabilities. The experimental relative probabilities compare favourably with the theoretical expectations, thus effectively mimicking a small scale quantum simulator.     

Particle Characterization by Projected Area Determination

The projected areas of non-spherical particles do not represent an unambiguous particle characteristic. Depending on the orientation towards a constant observational direction, different projected areas result. The spectrum of all projected area values of a particle, if determined representatively, gives the probability with which a certain value is obtained by a single measurement. In this work, the frequency distributions of different examples of test objects were both calculated and measured. The objects were a cube, a rectangular parallelepiped and also three model agglomerates consisting of spheres of the same size. Instead of just one projected area, during each measuring procedure three projected areas from three orthogonal directions can be obtained. A mean value is then calculated to reduce the ambiguity of the particle characteristic and enhance the resolution. A suitable measurement set-up is introduced. The results of calculation and measurement are compared for observation from just one direction and also simultaneous observation from three directions. The frequency distributions of the equivalent diameters of the particle projected areas show a characteristic trend of the total curve with remarkable properties. The simultaneous measurement of three values from mutually orthogonal directions and their mean value calculation result in a much narrower distribution. In this case, a non-sphericity factor can additionally be calculated, whose frequency distribution contains information in a characteristic manner about the degree to which the particle shape differs from a sphere.     

Quantum filtering one bit at a time

In this Letter we consider the purification of a quantum state using the information obtained from a continuous measurement record, where the classical measurement record is digitized to a single bit per measurement after the measurements have been made. Analysis indicates that efficient and reliable state purification is achievable for one- and two-qubit systems. We also consider quantum feedback control based on the discrete one-bit measurement sequences.     

基于光阻法的小光束截面粒径信息提取方法

为了实现同时兼顾大、小颗粒测量的液体颗粒计数,在分析细小光束照射下球形颗粒脉冲信号波形特征的基础上,提出了一种颗粒粒径信息提取方法,该方法通过对脉冲信号积分将颗粒脉冲信号的幅度与持续时间结合,可更加准确地提取颗粒的等效粒径信息.对理想脉冲信号进行数值模拟,并采用乳胶微粒标准物质进行实验测试,结果表明,该方法能够有效地提取大颗粒和小颗粒的粒径信息,从而拓宽了仪器检测范围.同时,分析了流速和噪声对该方法提取粒径准确性的影响,结果表明当流速波动小于10%时,测量误差小于5.41%;当噪声小于1%时,测量误差小于0.50%.     

外腔镜非线性运动对激光回馈应力测量系统精度的影响及修正

基于激光的回馈效应可实现光学材料应力分布的测量, 而系统外腔镜的非线性运动会引起测量结果的误差, 影响系统的精度. 利用高精度Nd:YAG激光回馈干涉仪对外腔镜的位移随时间的变化进行测量, 采用高次拟合的方式得到位移与时间函数关系, 并利用三镜腔等效模型的调谐曲线方程, 对非线性运动引入的应力测量误差进行计算, 实现对系统精度的修正. 结果表明: 外腔镜运动方向不同, 引起的误差呈现相反的变化趋势; 将不同方向的测量结果进行平均, 可减小系统的测量误差. 分析了外腔镜非线性运动带来的误差对系统测量精度的影响, 提出了测量误差修正方法, 对提高系统的测量精度具有重要意义.