Reconstruction of the time-dependent wave function exclusively from position data

A method is presented that reconstructs the amplitude and phase of an unknown time-dependent pure-state wave function entirely from experimental position data. No assumptions about the wave function are needed. At a series of times, a large collection of position data is taken, but no measurements of momentum or energy are necessary. The momenta, however, are required for the reconstruction of the wave function and are supplied by analysis of the position data via quantum particle trajectories. Simulations of the method are provided for helium atoms in single and double slit experiments.     

Quantum Fisher information and chaos in the Dicke model

We introduce a method of quantum tomography for a continuous variable system in position and momentum space. We consider a single two-level probe interacting with a quantum harmonic oscillator by means of a class of Hamiltonians, linear in position and momentum variables, during a tunable time span. We study two cases: the reconstruction of the wavefunctions of pure states and the direct measurement of the density matrix of mixed states. We show that our method can be applied to several physical systems where high quantum control can be experimentally achieved.     

基于多通道时间分辨光学层析成像系统的差分图像重建

报道了基于32通道时间分辨光学层析成像系统的差分图像重建结果,实验采用两个光参数与生物组织体大致相同的圆柱型模拟体,分别用于模拟新生儿头部和成人手臂,重建结果表明;采用差分测量的方法很好地重建出异质体的位置．尺寸及吸收系数相对于背景的变化;模拟和实验重建验证了所发展的二维,半三维重建算法的可行性;使用平均飞行时间作为数据类型,32个探测通道测量,比用强度作为数据类型或16通道测量更为准确地分出了两个相距20mm的异质体。结果表明目前的系统可以定性地重建出异质体的位置,尺寸,吸收系数的变化,展示该光学层析成像技术将在监测诸如血液含氧量变化,组织体涉氧新陈代谢等生理过程中具有良好应用前景,也对该种成像方法存在的问题及进一步改进的措施进行了讨论。     

Electron–positron momentum density distribution of Gd from 2D ACAR data via Maximum Entropy and Cormack’s methods

A successful application of the Maximum Entropy Method (MEM) to the reconstruction of electron–positron momentum density distribution in gadolinium out of the experimental of 2D ACAR data is presented. Formally, the algorithm used was prepared for two-dimensional reconstructions from line integrals. For the first time the results of MEM, applied to such data, are compared in detail with the ones obtained by means of Cormack’s method. It is also shown how the experimental uncertainties may influence the results of the latter analysis. Preliminary calculations, using WIEN2k code, of band structure and Fermi surface have been done as well.     

Exciton warming in III–V semiconductors and microcavities

We present a time resolved experiment in which we dynamically tailor the occupation and temperature of a photogenerated exciton distribution in QWs by excitation with two delayed picosecond pulses. The modification of the excitonic distribution results in ultrafast changes in the PL dynamics. Our experimental results are well accounted by a quasiequilibrium thermodynamical model, which includes the occupation and momentum distribution of the excitons. We use this model and the two-pulse experimental technique to study the polariton dynamics in InGaAs-based microcavities in the strong coupling regime. In particular, we demonstrate that resonantly injected upper polaritons mainly relax to the lower polariton branch via scattering to large momentum polariton states, producing the warming of the polariton reservoir.     

A computer controlled time resolved optical intensity profile measurement system

In this paper, a computer controlled system is described, which provides data management and position control for time resolved measurement of near and far field, along with charge carrier concentration distributions of semiconductor lasers. Of particular interest is the manner in which microprocessor control of inexpensive motorised micrometers is used to provide accurate repeatable movements on submicron scales. Due to its noise reduction capability through computer averaging, this system has been operated in conjunction with a 50 ps risetime photodiode, and thus is believed to allow time resolved measurement on the shortest reported timescales. The system provides a further advantage in that experimental data may be stored to give easy access for further processing.     

Study on distribution of electron momentum density and Fermi surface in lead by positron annihilation

The momentum density of electrons and the Fermi surface are measured in metal lead by the technique of positron annihilation. The three-dimensional electron-positron momentum distribution is reconstructed from measurements of the two-dimensional angular correlation of positron annihilation radiation (2D-ACAR), followed by the image reconstruction technique based on a direct Fourier transformation. On the basis of the obtained experimental spectrum, the Fermi surface topology, the high momentum components (HMC), the enhancement effect, and the autocorrelation function are discussed. The obtained experimental results are in good agreement with theoretical calculations.     

Direct space time-characterization of the electric fields of ultrashort optical pulses

We report the complete spatiotemporal characterization of ultrashort light pulses by use of a self-referencing device based on shearing interferometry in the space and frequency domains. The apparatus combines a spatially resolved spectral shearing interferometer with a spectrally resolved spatial shearing interferometer. The electric field as a function of one transverse spatial coordinate and time is obtained from a single experimental trace by means of a direct and fast algebraic phase reconstruction algorithm. The method has been tested in several common laboratory situations.     

近阈值下He原子的双电子电离实验中出射电子研究

利用适用于低能电子入射的反应显微成像谱仪，对电子入射He原子近阈值下的双电离过程进行了研究，实验测量了反应后3个粒子的全部动量，获得了出射电子间的关联信息.主要介绍近阈值下的双电离实验装置及实验技术，集中分析反应后出射电子的动量能量关系，对描述近阈值双电离的Wannier理论进行了检验，发现在入射电子能量为106eV时，实验结果具有Wannier理论预言的性质.     

Triggered qutrits for quantum communication protocols

A general protocol in quantum information and communication relies in the ability of producing, transmitting, and reconstructing, in general, qunits. In this Letter we show for the first time the experimental implementation of these three basic steps on a pure state in a three-dimensional space, by means of the orbital angular momentum of the photons. The reconstruction of the qutrit is performed with tomographic techniques and a maximum-likelihood estimation method. For the tomographic reconstruction we used more than 2400 different projections. In this way we also demonstrate that we can perform any transformation in the three-dimensional space.     

Substance identification by depth resolved spectroscopic pattern reconstruction in frequency domain optical coherence tomography

We analyze a method to extract additional depth resolved spectroscopic information from frequency domain optical coherence tomography (FDOCT) data. The reconstruction of depth resolved spectra is obtained by a Fourier transform of the individual peaks in the complex FDOCT depth profiles. We demonstrate a validation of this concept with theoretical simulations and with accurate experimental studies on a multilayer sample with four different characteristic absorbers. The spatially resolved spectroscopic patterns of all individual sample layers are calculated from the depth resolved reconstructed spectra. With an additional pattern recognition algorithm, these reconstructed patterns are compared automatically to the spectral characteristics of the expected substances. This provides an allocation of the reconstructed spectra to the substances with high reliability. Thus, we present an automated substance identification directly from conventional FDOCT data, which increases significantly the information content of the image.     

Study of low momentum track reconstruction for the BESⅢ main drift chamber

In order to overcome the difficulty brought by the circling charged tracks with transverse momentum less than 120 MeV in the BESⅢ Main Drift Chamber(MDC),a specialized method called TCurlFinder was developed.This tracking method focuses on the charged track reconstruction under 120 MeV and possesses a special mechanism to reject background noise hits.The performance of the package has been carefully checked and tuned by both Monte Carlo data and real data.The study shows that this tracking method could obviously enhance the reconstruction efficiency in the low transverse momentum region,providing physics analysis with more and reliable data.     

Molecular orbital theory and the assignment of charge transfer transitions

A survey of the present situation in the analysis of charge transfer transitions is given. The possibilities of the combinations of observable characteristics of charge transfer bands such as energy, intensity (including polarisation in a non-cubic system), band shape (including vibrational structure if resolved) and angular momentum properties by deriving molecular eigenvectors and by theoretical elaboration of experimental data of great number of halides and oxides are demonstrated.     

Observation of the orbital angular momentum spectrum of a light beam

We demonstrate an experimental scheme that allows the elucidation of the orbital angular momentum discrete spectrum of an arbitrary light signal. The orbital angular momentum spectrum is represented in a Laguerre-Gaussian mode base, and the spectral components are resolved in the frequency domain by exploiting the Doppler frequency shift that is imparted to rotating light beams.     

近红外漫射光层析成像实验研究

实验验证了所建立的时间分辨光学层析成像测量系统的光学参量预测能力、多个测量通道的一致性,表明了本测量系统具有层析成像的潜力.研究了采用特征数据量（平均飞行时间、广义脉冲谱技术为基础的用数据类型R）及全时间分辨数据的图像重建算法在光学参量重建准确度、重建出的对象尺寸、空间分辨率等方面的各自优势.     

Observation of microscopic CO dynamics on Cu(001) using 3He spin-echo spectroscopy

We present momentum resolved measurements of quasielastic helium atom scattering made using a new 3He spin-echo spectrometer. Our data for the dynamics of CO on Cu(001) indicates an activated jump mechanism which we analyze in detail using molecular dynamics simulations. A nearly isotropic potential energy surface is found with an average barrier height of approximately 125 meV, yielding comparable hopping rates along both the <110> and <100> directions. The measurements provide the first rigorous experimental test of state-of-the-art first-principles calculations previously made on this system.     

Detecting the amplitude mode of strongly interacting lattice bosons by Bragg scattering

We report the first detection of the Higgs-type amplitude mode using Bragg spectroscopy in a strongly interacting condensate of ultracold atoms in an optical lattice. By the comparison of our experimental data with a spatially resolved, time-dependent bosonic Gutzwiller calculation, we obtain good quantitative agreement. This allows for a clear identification of the amplitude mode, showing that it can be detected with full momentum resolution by going beyond the linear response regime. A systematic shift of the sound and amplitude modes' resonance frequencies due to the finite Bragg beam intensity is observed.     

An extended segment pattern dictionary for a pattern matching tracking algorithm at BESⅢ

A pattern matching based tracking algorithm, named MdcPatRec, is used for the reconstruction of charged tracks in the drift chamber of the BESⅢ detector. This paper addresses the shortage of segment finding in the MdcPatRec algorithm. An extended segment construction scheme and the corresponding pattern dictionary are presented. Evaluation with Monte-Carlo and experimental data show that the new method can achieve higher efficiency for low transverse momentum tracks.     

虚拟和真实实验相融合的三维非完全数据层析

为了解决非完全数据条件下复杂流场的三维层析重建,结合计算流体力学(Computational fluid dynamics,CFD)、计算流动显示技术(Computational flo wimaging,CFI)和光学层析技术(Optical computerized tomography,OCT),提出了应用于非完全数据流场重建的虚拟实验和真实实验相融合(即CFD,CFI与OCT融合)的三维层析。非对称双峰温度场实验结果表明,与完全数据重建结果相比,虚拟实验与真实实验相融合的三维层析的重建双峰误差小于5％。因此能够更好地实现非完全数据条件下流场的三维重建,极大地提高非完全数据条件下流场重建的真实性,较好地与实际结果相吻合,从而为解决有限角条件下的严重非完全数据流场的重建开拓了一条新途径。