Quantum correlations and entanglement in coupled optomechanical resonators with photon hopping via Gaussian interferometric power analysis

Quantum correlations that surpass entanglement are of great importance in the realms of quantum information processing and quantum computation.Essentially,for quantum systems prepared in pure states,it is difficult to differentiate between quantum entanglement and quantum correlation.Nonetheless,this indistinguishability is no longer holds for mixed states.To contribute to a better understanding of this differentiation,we have explored a simple model for both generating and measuring these quantum correlations.Our study concerns two macroscopic mechanical resonators placed in separate Fabry–Pérot cavities,coupled through the photon hopping process.this system offers a comprehensively way to investigate and quantify quantum correlations beyond entanglement between these mechanical modes.The key ingredient in analyzing quantum correlation in this system is the global covariance matrix.It forms the basis for computing two essential metrics:the logarithmic negativity(E_(N)^(m))and the Gaussian interferometric power(P_(G)^(m)).These metrics provide the tools to measure the degree of quantum entanglement and quantum correlations,respectively.Our study reveals that the Gaussian interferometric power(P_(G)^(m))proves to be a more suitable metric for characterizing quantum correlations among the mechanical modes in an optomechanical quantum system,particularly in scenarios featuring resilient photon hopping.

Photon Correlation Spectroscopy and SAXS Study of Mixture of NaCl with AOT Microemulsion at X = 6.7

Photon Correlation Spectroscopy is used to study the AOT microemulsion with and without NaCl. Collective diffusion coefficient was investigated by Photon Correlation Spectroscopy technique. We have studied effect of charge on dynamic of water-in-oil microemulsion (nano-droplet of water to the oil), which stabilized by AOT and dispersed in n-Decane at water/AOT with 6.7 molar ratio. The small angle X-ray scattering technique and hard sphere model were used to study the structural information of AOT microemulsion with and without NaCl. The structural investigation of samples shows a decrease of length scale of cylindrical droplets with increasing of NaCl concentration in AOT microemulsion.

Photon Correlation Spectroscopy and SAXS Study of Cylindrical to Spherical Transition in the AOT Microemulsion by Changing Solvent

We study dynamic and structure of nano-droplets of AOT/water/oil microemulsion with different oils at water/AOT molar ratio of 6.7. Photon correlation spectroscopy is used to study collective diffusion coefficient of nano-droplets at AOT microemulsion with decane and cyclohexane. The collective diffusion coefficient of nanodroples is increasing with change of oil from decane to cyclohexane. The structure of AOT microemulsion with decane and cyclohexane is founded with SAXS. Our results show, nano-droplets of AOT microemulsion with decane at X = 6.7 have cylindrical structure and AOT microemulsion with cyclohexane at X = 6.7 have spherical structure.

Effects of electron correlation and the Breit interaction on one- and two-electron one-photon transitions in double K hole states of He-like ions(10 ≤ Z ≤ 47)

The x-ray energies and transition rates associated with single and double electron radiative transitions from the double K hole state 2s2p to the 1s2s and 1s^2 configurations of 11 selected He-like ions(10 ≤ Z ≤ 47) are calculated using the fully relativistic multi-configuration Dirac–Fock method(MCDF). An appropriate electron correlation model is constructed with the aid of the active space method, which allows the electron correlation effects to be studied efficiently. The contributions of the electron correlation and the Breit interaction to the transition properties are analyzed in detail. It is found that the two-electron one-photon(TEOP) transition is correlation sensitive. The Breit interaction and electron correlation both contribute significantly to the radiative transition properties of the double K hole state of the He-like ions. Good agreement between the present calculation and previous work is achieved. The calculated data will be helpful to future investigations on double K hole decay processes of He-like ions.

一种对高速运动目标的单光子测距方法

作为一种前沿的激光探测技术,单光子激光测距技术已成功应用于月球测距、卫星测距和地面测高等领域。然而,单光子测距在机载空对空、地对空平台上对高速运动目标进行跟踪测距时,回波光子落在不同的时间窗,导致直接计数无法有效提取信号的问题仍需解决。针对空对空条件下单光子激光测距的应用需求,基于时间相关光子计数技术设计一种适用于全天时、宽时域、多噪声条件下对高速运动目标的单光子测距方法。该方法采用阵列单光子探测器和相邻时间窗相关统计多帧处理算法提取激光回波光子信号,并在Matlab平台上对算法进行仿真实验,使用多元阵列单光子探测器实现最大测程百公里以上、背景噪声计数率约为5 MHz、单脉冲回波光子计数平均值为1条件下的回波光子信号提取。该方法能够克服传统单光子探测只能对准静态目标测距,只能在小接收视场和小波门范围等弱背景噪声及目标轨迹可预测条件下应用的限制,将单光子探测由只能固定平台夜晚对准静态目标测距推广至通用平台全天时对高速运动目标测距。

488nm泵浦的自发参量下转换特性研究

自发参量下转换的光谱、光子数率和时间相关性对宽波段光电探测器定标具有重要意义。本文理论模拟了488 nm连续激光泵浦偏硼酸钡(BBO)晶体的光谱和光子数率的分布,搭建了光谱、光子数率和时间相关性测量的实验系统。基于理论研究,BBO晶体的相位匹配角选择24.3184°,可实现605~2523 nm连续宽波段相关光子制备,光子数率最大值为4.2716×10^(7) s^(-1)。采用CMOS相机和光电倍增管测量相关光子圆环和光子数率,根据波长和探测器响应波段来选择相应的光电探测器,以测量时间相关性。实验测量得到605~1000 nm波段的相关光子光谱,光子数率的实测值与理论值偏差在1个量级内,并观察到710~1560 nm波段的符合峰。实验结果验证了所建立的理论模型的正确性、自发参量下转换过程的宽光谱特性和时间相关性,为实现可见-近红外波段的宽光谱相关光子定标提供了研究基础。

Traditional Chinese Medicine-Based Subtyping of Early-Stage Type 2 Diabetes Using Plasma Metabolomics Combined with Ultra-Weak Photon Emission

The prevalence of type 2 diabetes mellitus(T2DM)is increasing rapidly worldwide.Because of the limited success of generic interventions,the focus of the disease study has shifted toward personalized strategies,particularly in the early stages of the disease.Traditional Chinese medicine(TCM)is based on a systems view combined with personalized strategies and has improved our knowledge of personalized diagnostics.From a systems biology perspective,the understanding of personalized diagnostics can be improved to yield a biochemical basis for such strategies;for example,metabolomics can be used in combination with other system-based diagnostic methods such as ultra-weak photon emission(UPE).In this study,we investigated the feasibility of using plasma metabolomics obtained from 44 pre-T2DM subjects to stratify the following TCM-based subtypes:Qi-Yin deficiency,Qi-Yin deficiency with dampness,and Qi-Yin deficiency with stagnation.We studied the relationship between plasma metabolomics and UPE with respect to TCM-based subtyping in order to obtain biochemical information for further interpreting disease subtypes.Principal component analysis of plasma metabolites revealed differences among the TCM-based pre-T2DM subtypes.Relatively high levels of lipids(e.g.,cholesterol esters and triglycerides)were important discriminators of two of the three subtypes and may be associated with a higher risk of cardiovascular disease.Plasma metabolomics data indicate that the lipid profile is an essential component captured by UPE with respect to stratifying subtypes of T2DM.The results suggest that metabolic differences exist among different TCM-based subtypes of pre-T2DM,and profiling plasma metabolites can be used to discriminate among these subtypes.Plasma metabolomics thus provides biochemical insights into system-based UPE measurements.

Photon statistics of pulse-pumped four-wave mixing in fiber with weak signal injection

We study the photon statistics of pulse-pumped four-wave mixing in fibers with weak coherent signal injection by measuring the intensity correlation functions of individual signal and idler fields. The experimental results show that the intensity correlation function of individual signal（idler） field g_（s（i））^（2） decreases with the intensity of signal injection. After applying narrow band filter in signal（idler） band, the value of g_（s（i））^（2） decreases from 1.9 ± 0.02（1.9 ± 0.02） to 1.03 ± 0.02（1.05 ± 0.02） when the intensity of signal injection varies from 0 to 120 photons/pulse. The results indicate that the photon statistics changes from Bose–Einstein distribution to Poisson distribution. We calculate the intensity correlation functions by using the multi-mode theory of four-wave mixing in fibers. The theoretical curves well fit the experimental results.Our investigation will be useful for mitigating the crosstalk between quantum and classical channels in a dense wavelength division multiplexing network.

Spin Supercurrent in Phenomena of Quantum Non-Locality (Quantum Correlations, Magnetic Vector Potential) and in Near-Field Antenna Effect

It is shown that such phenomena as quantum correlations (interaction of space-separated quantum entities), the action of magnetic vector potential on quantum entities in the absence of magnetic field, and near-field antenna effect (the existence of superluminally propagating electromagnetic fields) may be explained by action of spin supercurrents. In case of quantum correlations between quantum entities, spin supercurrent emerges between virtual particles pairs (virtual photons) created by those quantum entities. The explanation of magnetic vector potential and near-field antenna effect is based on contemporary principle of quantum mechanics: the physical vacuum is not an empty space but the ground state of the field consisting of quantum harmonic oscillators (QHOs) characterized by zero-point energy. Using the properties of the oscillators and spin supercurrent, it is proved that magnetic vector potential is proportional to the moment causing the orientation of spin of QHO along the direction of magnetic field. The near-field antenna effect is supposed to take place as a result of action of spin supercurrent causing secondary electromagnetic oscillations. In this way, the electromagnetic field may spread at the speed of spin supercurrent. As spin supercurrent is an inertia free process, its speed may be greater than that of light, which does not contradict postulates of special relativity that sets limits to the speed of inertial systems only.

Bell Correlations from Local Un-Entangled States of Light and Quantum Electro-Dynamics

Based on the Bell theorem, it has been believed that a theoretical computation of the Bell correlation requires explicit use of an entangled state. Such a physical superposition of light waves occurs in the down-converter sources used in Bell experiments. However, this physical superposition is eliminated by wave propagation to spatially separated detectors. Bell correlations must therefore result from local waves, and the source boundary conditions of their previously entangled state. In the present model, Bell correlations are computed from disentangled separated waves, boundary conditions of nonlinear optics, and properties of single-photon and vacuum states specified by quantum electrodynamics. Transient interference is assumed between photon-excited waves and photon-empty waves based on the possibility of such interference found to be necessary by the designers of Bell-experiment sources. The present model employs local random variables without specifying underlying causality.

光子计数激光雷达的自适应时空关联深度估计

光子计数激光雷达具有高灵敏度、高时间分辨率等优势,为了实现在大量回波数据及强噪声环境下目标信息的高效提取,提出一种自适应时空关联深度估计算法。首先,根据回波数据中信号光子和噪声光子与发射激光脉宽的关系,利用回波光子在时域上的统计差异,自适应重构具有不同时间分辨率的直方图,并结合邻域像素数据之间的空间关联性,自适应调整时间窗口的大小,寻找信号光子所在的时间区间并提取相应的数据,显著降低后续处理的数据量;其次,基于所提取的回波光子数据,设置滑动窗口初步估计各像素的时间值;最后,通过自适应均值滤波得到各像素的飞行时间,解算相应的距离信息。相较于峰值法和Chen算法,在起伏地形探测的仿真实验中,当信号光子数约为14、噪声强度小于6 MHz时,重建的均方误差至少降低了20%;在室内静态目标成像实验中,当噪声强度在5.08 MHz范围内,所提算法进行目标重建的最大均方误差为0.017。仿真及实验结果表明,所提算法对强噪声下起伏地形和室内静态目标探测的回波数据均具有较好的滤波效果。

基于计算机仿真的复合光功能树脂的设计

基于计算机仿真技术,结合蒙特卡罗算法和光学理论,研究了荧光粒子粒径和用量对复合光功能树脂光通量、相关色温、光子平均自由程和色坐标等的影响规律。结果表明:复合光功能树脂的光通量随着荧光粒子粒径的增大先升高后降低,相关色温和光子平均自由程则由于粒子数目降低而逐渐升高,在粒径为9μm时具有最大光通量(150.69 lm);复合光功能树脂的光通量随着荧光粒子用量的增加先升高后降低,相关色温和光子平均自由程则由于粒子数目升高而逐渐降低,在荧光粒子质量分数为8.5%时具有最大光通量(149.26 lm)。进一步结合色坐标与黑体辐射曲线的相对位置得到荧光粒子最佳粒径为12μm,最佳用量为6.0%(w),此时对应色坐标x=0.379 1,y=0.383 2,相关色温4 588 K,光通量144.95 lm。

基于单光子探测的光子计数光时域反射仪研究进展

基于光时域反射技术(Optical Time Domain Reflectometry, OTDR)的光纤分布式传感器可以实现对整个传感光纤空间可分辨的分布式测量,相比点式传感器具有极大的技术及应用成本优势。而传统的基于模拟探测的OTDR光纤分布式传感器在空间分辨率及动态范围上存在性能瓶颈。基于单光子探测的光子计数OTDR光纤分布式传感系统通过数字化的探测和记录方式,可以突破传统OTDR系统的性能极限。本文对光子计数OTDR系统技术及发展进行了综述,旨在通过本文的综述,明确基于单光子探测的光子计数OTDR系统的优势及限制,以及该技术的未来发展趋势,促进基于OTDR技术的光纤分布式传感器的进一步发展。

时空域联合编码扩频单光子计数成像方法

本文结合空间编码单像素成像技术和扩频时间编码扫描成像技术,提出一种时空域联合编码扩频单光子计数成像方法.该方法具备可避免距离模糊、大时宽带宽积的优势,并且在噪声干扰下,能够准确恢复距离像.本文推导了基于单光子探测的时空域联合相关非线性探测模型、成像正向模型和信噪比模型,并通过凸优化反演算法恢复深度图像,理论模型和仿真实验均证明,与传统的基于空间编码的单像素成像方法相比,本方法提高了重建的质量.其中,采用m序列作为时间编码,成像的噪声鲁棒性更高.和传统的空间编码单像素成像技术相比,本文提出方法的成像均方误差降低了4/5,引入二次相关方法后,成像均方误差降低了9/10.本文所提出的成像架构为非扫描激光雷达成像方法提供了新思路.

相关光子自校准微光辐亮度计的光学设计

为满足气候监测、微光辐射计量、单光子计量等定量应用需求,设计了基于相关光子自校准的紧凑型三通道微光辐亮度计,其光谱范围为460~1550nm,辐亮度测量范围为1×10^(-9)~1×10^(-6)W/(cm^(2)·sr·nm)。设计时考虑整机的集成化、小型化和模块化,将8个光谱波段集成为三通道结构。其中可见光近红外波段采用自由空间耦合,短波红外波段采用多模光纤耦合方式。通过设计优化分析,微光辐亮度计的第一、二通道的聚焦光斑满足Si单光子探测器光敏面300μm像元要求,第三通道的聚焦光斑满足多模光纤62.5μm芯径和0.22数值孔径要求,三个通道的聚焦光斑均可被单光子探测器光敏面接收,满足设计目标,可为后续的工程化应用提供参考。

基于相关光子对的单光子探测器量子效率校准技术研究

随着量子技术的发展,对极微弱光辐射的研究方向逐渐向量子化发展,利用相关光子对法对单光子探测器的相关参数进行测量。介绍了相关光子对法的原理及相关光子源中非线性晶体的关键参数设计方法,利用波长355 nm的激光器作为泵浦光源,泵浦相位匹配角为36°的BBO非线性晶体,实现了(450~1 675)nm的相关光子输出;泵浦相位匹配角为28.1°,32.91°,31.29°的BBO非线性晶体,实现了460 nm和1 550 nm,632.8 nm和807 nm,1 064 nm和532 nm的相关光子对共线输出。在460 nm,1 550 nm,632.8 nm,1 064 nm波长点利用符合测量对单光子探测器的量子效率进行测量,为实现多波长点至全波段单光子探测器校准奠定基础。

均匀圆阵下微波光子鉴相相关干涉仪测向算法

为实现高频段微波信号的精确测向,提出了一种基于微波光子鉴相器的均匀圆阵相关干涉仪测向算法。为克服传统的电域鉴相器工作频段低、带宽窄的缺点,利用微波光子技术高频段、大带宽、低损耗和抗电磁干扰的优点,基于双偏振调制器设计一种微波光子鉴相器,利用光干涉将相位差信息映射为光信号功率,通过测量功率计算出相位差。该微波光子鉴相器精度高,能实现±180°的相位差测定,鉴相精度为±2°。利用余弦函数克服了传统相关干涉仪存在的相位模糊问题。同时,为确保算法的实时性,测向算法需选取适当的步进角度。为克服步进角度引入的测向误差,利用二维抛物面进行拟合插值运算,从而提高算法的精确度。最后,通过仿真验证了微波光子鉴相器和相关干涉仪测向算法的有效性。

宽波段平场复消色差显微物镜设计

目前商品化的显微物镜的适用波段范围无法满足360~1000 nm波段范围的相关光子光斑的测量要求。从复消色差基础理论出发,研究了复消色差玻璃组合的选择方法,得到了二级光谱校正效果较好的玻璃组合。采用全球面折射式、无穷远校正的结构型式,设计出一款放大倍率为20倍、数值孔径为0.3、工作距离为10 mm、齐焦距为60 mm、视场为0.66 mm、工作波长范围为360~1000 nm的平场复消色差显微物镜。调制传递函数曲线在80 lp/mm处接近衍射极限,场曲校正满足平场的国际标准,其余成像指标也接近衍射极限。公差分析结果表明,该显微物镜满足设计和实际加工要求。

High-performance eight-channel system with fractal superconducting nanowire single-photon detectors

Superconducting nanowire single-photon detectors(SNSPDs)have become a mainstream photon-counting technology that has been widely applied in various scenarios.So far,most multi-channel SNSPD systems,either reported in literature or commercially available,are polarization sensitive,that is,the system detection efficiency(SDE)of each channel is dependent on the state of polarization of the to-be-detected photons.Here,we reported an eight-channel system with fractal SNSPDs working in the wavelength range of 930 to 940 nm,which are all featured with low polarization sensitivity.In a close-cycled Gifford-McMahon cryocooler system with the base temperature of 2.2 K,we installed and compared the performance of two types of devices:(1)SNSPD,composed of a single,continuous nanowire and(2)superconducting nanowire avalanche photodetector(SNAP),composed of 16 cascaded units of two nanowires electrically connected in parallel.The highest SDE among the eight channels reaches 96+^(4)_(-5%),with the polarization sensitivity of 1.02 and a dark-count rate of 13 counts per second.The average SDE for eight channels for all states of polarization is estimated to be 90±5%.It is concluded that both the SNSPDs and the SNAPs can reach saturated,high SDE at the wavelength of interest,and the SNSPDs show lower dark-count(false-count)rates,whereas the SNAPs show better properties in the time domain.With the adoption of this system,we showcased the measurements of the second-order photon-correlation functions of light emission from a singlephoton source based on a semiconductor quantum dot and from a pulsed laser.It is believed that this work will provide new choices of systems with single-photon detectors combining the merits of high SDE,low polarization sensitivity,and low noise that can be tailored for different applications.

Improved generation of correlated photon pairs from monolayer WS_2 based on bound states in the continuum

Entangled photons are the fundamental resource in quantum information processing. How to produce them efficiently has always been a matter of concern. Here we propose a new way to produce correlated photons efficiently from monolayer WS_2 based on bound states in the continuum(BICs). The BICs of radiation modes in the monolayer WS_2 are realized by designing the photonic crystal slab-WS_2-slab structure. The generation efficiency of correlated photon pairs from such a structure has been studied by using a rigorous quantum model of spontaneous parametric down-conversion with the plane wave expansion method. It is found that the generation efficiency of correlated photon pairs is greatly improved if the signal and idler fields are located at the BICs determined by the inverse scattering matrix of the structure. This is in contrast to the parametric down-conversion process for the enhanced generation of nonlinear waves if the pump field is located at the BICs determined by the scattering matrix of the structure. The generation rate of the correlated photon pairs can be improved by 7 orders of magnitude in some designed structures. The generated quantum signals are sensitive to the wavelength and exhibit narrowed relative line width, which is very beneficial for quantum information processing.