同步脉冲发生器

本文介绍一种高精度同步脉冲发生器,可用于同时触发多台仪器的测试系统中.其任意两路输出脉冲之间的分散性小于0.5ns.     

序列光脉冲光谱的非同步采集

本文描述了序列光脉冲光谱的非同步采集原理和方法，并就实际光源进行测量，给出测量结果。     

脉冲辐射探测技术

脉冲辐射探测是探知核反应过程特征信息的主要途径之一,是核反应过程特性研究、核装置设计、运行、监测与控制不可或缺的技术手段。由核探测器、探测方法和应用技术等构成的脉冲辐射场探测技术,已成为科学研究、核技术应用、核材料分析、裂变/聚变研究和天体物理等相关核科学研究的必备技术元素。文章介绍了我国发展的瞬态核裂变、核聚变反应过程释放的脉冲中子、伽马混合辐射场探测系统和测量技术。     

兰绿脉冲激光用于海深及水下目标探测

本文扼要介绍了美国Hickman等人就机载兰绿激光浊水深度测绘所进行的实验研究及所建立的理论模型。他们所做的海上实验表明,现场测量数据与理论模型预期的结果大体相符。     

脉冲激光频域干涉技术在泵浦探测实验中的应用

通过对频域干涉原理的深入研究,本文提出了一种超快时间分辨力的脉冲激光频域干涉技术.采用该技术方法可精确同步泵浦-探测实验中泵浦脉冲和探测脉冲的传输时间,其同步精度与脉冲激光器脉宽相当.本文详细论述了频域干涉技术的系统构成和工作原理,数值模拟了飞秒脉冲激光频域干涉仪的输出信号,指出当频域干涉仪输出的条纹数最少时,两脉冲之间的传输时间差即达到最小,最后通过动态实验验证了理论推导结果.     

序列光脉冲光谱的非同步采集

西方描核实 了序列光脉冲光谱的非同步采集原理和方法，并京实际光源进行测量，给出测量结果。     

宏/子脉冲编码光子计数激光雷达

光子计数激光雷达因其极高的探测灵敏度在远距离目标探测领域有着非常重要的作用。针对远距离、高速度的目标,普通的光子计数激光雷达无法简单通过统计直方图获得有用的回波信息。为了解决这一问题,本文提出了一种基于宏/子脉冲编码的光子计数激光雷达,利用时移脉冲累加的方法提取子脉冲的飞行时间进而在一个宏脉冲内获得目标距离信息。建立了宏/子脉冲编码光子计数激光雷达的理论模型,对虚警概率和探测概率的影响进行了分析,并通过蒙特卡洛仿真和实验验证了其对远距离高速径向运动目标探测的有效性。

     

在地层探测中应用互补码脉冲压缩技术的研究

一个适用于海洋地层探测的互补信号发生和处理系统已经研制成功。其实施方案是：声源交替地发射一对互补码信号中的两个互补部份，接收机相应地进行回波信号的实时相关处理，然后再在时间上一一对应地把相邻两次的相关处理输出实时相加，就得到无旁辨的终端输出在地层探测图上显示。波浪起伏会对回波到达时间和信号码之间隔进行调制，由此产生的“去互补”和“去相关”效应会降低互补码信号处理的性能。本文着重研究了这个问题，并通过计算机模拟证实了在实际的海洋地层探测中应用互补码脉冲压缩技术的有效性。     

除颤监护仪同步脉冲与除颤脉冲的延迟时间探究

<正>我院有某世界著名品牌除颤监护仪多台,在委托宁波市计量院进行性能质量检测时,发现在同步模式下延迟时间的测试项目合格率偏低。25台同一型号除颤监护仪,有18台不合格。而不合格的18台除颤监护仪中,延迟时间在31ms~35ms之间;7台合格的,5台的延迟时间为30ms,2台为29ms。JJF1149-2006《心脏除颤器和心脏除颤监护仪校准规范》规定,同步模式下除颤时,除颤脉冲应只在出现同步脉冲时才能出现,     

浅海水声信道的脉冲噪声特性分析

1问题提出在沿岸浅海,声波由海面和海底不断反射而传播,其多径效应非常显著。浅海中还存在着大量散射体以及起伏不平的界面,其散射效应严重[1,2]。另外,浅海里还有大量海洋生物的活动以及海风的影响,     

Interference in the Single Photon Regime

Abstract

The two orthogonally polarized modes of a Zeeman laser can be combined at a polarizing beam-splitter to produce two outputs at the difference frequency. This paper presents some observations on these beats in the classical limit and in the single photon regime, where the mean separation of the photons exceeds the optical path length, and discusses their implications.     

Single Side Imaging of Corrosion Under Insulation Using Single Photon Gamma Backscattering

In this work, a gamma ray Compton backscatter technique is used for imaging defects and thickness variations in insulated pipes and metal plates containing depressions of various diameters and at various depths from one side of the object. The scattered radiation was measured by a scintillation detector that scans the object using a two-dimensional mechanical scanning system. The gamma spectrum was displayed with a multichannel analyzer (MCA), and the energy window width was selected so that only Compton single scatter counts were measured. Images were constructed using the LabVIEW computer program. Successful images of defects on the outer surface of the object under the insulation were obtained, and the system was found to be able to detect wall thickness changes in large pipes with walls more than 15 mm thick. Low activity sources of 10⁸ Bq (a few mCi) were used, and the dose rate near the surface is four orders of magnitude lower than conventional industrial radiography sources, permitting it to be much safer.     

Dark Count Suppression in Superconducting Nanowire Single Photon Detectors

One of the important performance parameters of superconducting nanowire single photon detectors (SNSPD) is the dark count rate. Dark counts are related to thermally-activated hopping of magnetic vortices across the nanowire. We present an experimental analysis of how the thermal coupling of the NbN SNSPD to the heat sink affects the dark count rate. It was found that the rate decreases with the increase in coupling strength while the detection efficiency remains almost constant.     

Quantum Electronic Contract Scheme Based on Single Photon

An electronic contract is a contract signed by electronic means, which is widely used in electronic commerce activities. In recent years, with the rapid development of quantum cryptography technology, the quantum electronic contract has been widely studied by researchers. Supported by the basic principles of quantum mechanics, a quantum electronic contract scheme based on the single photon is proposed in this paper. In this scheme, two copies of the same contract are signed by both parties involved, and then a copy of each contract is sent to a trusted third party. The trusted third party verifies the signatures of both parties and compares the signed copies to determine whether the contract is valid. Compared with the previous scheme, this scheme is based on the quantum electronic contract signed by the single photon. Because the single photon is easy to prepare and operate, this scheme is simple and easy to implement. At the same time, the scheme does not need to exchange signatures between the two parties, which reduces the complexity of communication. Nevertheless, it requires both parties and the third party to be honest and trustworthy.     

Multiplexing Superconducting Qubit Circuit for Single Microwave Photon Generation

We report on a device that integrates eight superconducting transmon qubits in \(\lambda /4\) superconducting coplanar waveguide resonators fed from a common feedline. Using this multiplexing architecture, each resonator and qubit can be addressed individually, thus reducing the required hardware resources and allowing their individual characterisation by spectroscopic methods. The measured device parameters agree with the designed values, and the resonators and qubits exhibit excellent coherence properties and strong coupling, with the qubit relaxation rate dominated by the Purcell effect when brought in resonance with the resonator. Our analysis shows that the circuit is suitable for generation of single microwave photons on demand with an efficiency exceeding 80%.     

Ir TES Electron-Phonon Thermal Conductance and Single Photon Detection

We have operated an Ir TES as detector for single photon at 450 nm in a temperature range of 100–120 mK. The decoupling of the electron gas from the phonons in the film, caused by the fifth power dependence of the temperature, is measured from the pulse decay time. The detection of single photon generated by a laser diode with a pulse length of 500 ns in a 25×25 μm² detector area at a base temperature of 90 mK is shown.      

Characterization of Superconducting Single Photon Detectors Fabricated on MgO Substrates

Electrical and optical characterization has been performed on several superconducting single photon detectors (SSPDs) consisting of meanders made of ultrathin NbN films. The NbN films, with thickness ranging from 150 nm to 3 nm, were deposited by dc magnetron sputtering on MgO substrates kept at temperature T=400°C. This deposition process carried out at low temperature opens the way of monolithic integration with other photonic devices. The superconducting properties of NbN films and the critical design parameters that affect the quantum efficiency (QE) have been optimized. In particular, by measuring the switching current distribution of each stripe of the meander the process uniformity has been studied. Optical measurements on the fabricated SSPDs showed a QE ≈20% at 4.2 K for photons with a wavelength of 1300 nm.      

Superconducting Single Photon Nanowire Detectors Development for IR and THz Applications

We present our progress in the development of superconducting single-photon detectors (SSPDs) based on meander-shaped nanowires made from few-nm-thick superconducting films. The SSPDs are operated at a temperature of 2–4.2 K (well below T _c ) being biased with a current very close to the nanowire critical current at the operation temperature. To date, the material of choice for SSPDs is niobium nitride (NbN). Developed NbN SSPDs are capable of single photon counting in the range from VIS to mid-IR (up to 6 μm) with a record low dark counts rate and record-high counting rate. The use of a material with a low transition temperature should shift the detectors sensitivity towards longer wavelengths. We present state-of-the art NbN SSPDs as well as the results of our recent approach to expand the developed SSPD technology by the use of superconducting materials with lower T _c , such as molybdenum rhenium (MoRe). MoRe SSPDs first were made and tested; a single photon response was obtained.      

Depth of Field Measurements Relevant to Single Photon Detection Using Image-intensified Microscopy

The problems of defining a depth of field d _p when individual photons emitted in a low-level luminescent process are recorded via an image-intensified microscope are discussed. Simulation studies of a self-luminous cylindrical volume source whose axis lies along the optical axis of the microscope were carried out by moving a uniformly-illuminated pinhole along the optical axis, and arranging for its in-focus image to fill exactly a circular light detector. The detector output plotted against pinhole position is approximately Gaussian in form for the objectives studied (from 10 2 /0·25 to 74 2 /0·65), and d _p is defined as the full width at half maximum. These values of d _p adequately fit the theoretical relation d _p = 2·45 R/tan sin^-1(NA/n), where NA is the numerical aperture of the objective and n is the refractive index of the immersion medium. With spherical, or near-spherical, volume sources d _p is usually significantly greater than the volume of the source. The problems of defining a depth of field p when individual photons emitted in a low-level luminescent process are recorded via an image-intensified microscope are discussed. Simulation studies of a self-luminous cylindrical volume source whose axis lies along the optical axis of the microscope were carried out by moving a uniformly-illuminated pinhole along the optical axis, and arranging for its in-focus image to fill exactly a circular light detector. The detector output plotted against pinhole position is approximately Gaussian in form for the objectives studied (from 10 2 /0·25 to 74 2 /0·65), and d _p is defined as the full width at half maximum. These values of d _p adequately fit the theoretical relation d _p = 2·45 R/tan sin^-1(NA/n), where NA is the numerical aperture of the objective and n is the refractive index of the immersion medium. With spherical, or near-spherical, volume sources d _p is usually significantly greater than the volume of the source.     

基于时间相关单光子计数的非接触式荧光层析成像系统

基于时间相关单光子计数(TCSPC)技术原理,研究了一套面向早期乳腺癌检测的时域荧光层析成像系统,系统采用非接触式空间光扫描测量方式,相对于传统的光纤接触式测量方法,可增大空间采样量、减小测量误差、提高空间分辨率.通过仿体实验对系统的成像质量进行了验证,结果表明:单目标仿体实验能较好地对荧光产率与寿命进行重建;在双目标仿体荧光产率的重建中,可有效对中心距为20mm、边距为15mm的目标体进行分辨,且对不同浓度荧光剂目标的重建具有较好的线性.实验结果证明系统应用于乳腺检测的可行性,进一步发展可有望应用于临床乳腺成像中.