Reconstructing unknown quantum states using variational layerwise method

In order to gain comprehensive knowledge of an arbitrary unknown quantum state, one feasible way is to reconstruct it, which can be realized by finding a series of quantum operations that can refactor the unitary evolution producing the unknown state. We design an adaptive framework that can reconstruct unknown quantum states at high fidelities, which utilizes SWAP test, parameterized quantum circuits (PQCs) and layerwise learning strategy. We conduct benchmarking on the framework using numerical simulations and reproduce states of up to six qubits at more than 96% overlaps with original states on average using PQCs trained by our framework, revealing its high applicability to quantum systems of different scales theoretically. Moreover, we perform experiments on a five-qubit IBM Quantum hardware to reconstruct random unknown single qubit states, illustrating the practical performance of our framework. For a certain reconstructing fidelity, our method can effectively construct a PQC of suitable length, avoiding barren plateaus of shadow circuits and overuse of quantum resources by deep circuits, which is of much significance when the scale of the target state is large and there is no a priori information on it. This advantage indicates that it can learn credible information of unknown states with limited quantum resources, giving a boost to quantum algorithms based on parameterized circuits on near-term quantum processors.     

Controlled unknown quantum operations on hybrid systems

Any unknown unitary operations conditioned on a control system can be deterministically performed if ancillary subspaces are available for the target systems [Zhou X Q, et al. 2011 Nat. Commun. 2 413]. In this paper, we show that previous optical schemes may be extended to general hybrid systems if unknown operations are provided by optical instruments. Moreover, a probabilistic scheme is proposed when the unknown operation may be performed on the subspaces of ancillary high-dimensional systems. Furthermore, the unknown operations conditioned on the multi-control system may be reduced to the case with a control system using additional linear circuit complexity. The new schemes may be more flexible for different systems or hybrid systems.     

缅甸翡翠化学成分的变化对其红外光谱的影响

缅甸翡翠是以硬玉为主要矿物的多晶集合体,硬玉的晶体化学成分可以用NaAlSi₂O₆来表示,天然产出的硬玉常常存在类质同象替代,Na被Ca替代,Al被Mg,Fe,Cr等元素替代,形成不同的翡翠类型,使得翡翠的化学成分变得更加复杂,而且其物理性质也产生变化,这种变化包括颜色、透明度、折射率、比重、结晶程度以及红外吸收光谱的特征。探索了翡翠的化学成分对其红外光谱的影响及规律,使用傅里叶红外光谱仪(Fourier transform infrared spectroscopy, FTIR）对10个含不同化学成分的缅甸翡翠样品进行漫反射法测量,分析结果表明,翡翠的红外吸收峰的位置随着样品的Na/Na+Ca的摩尔比例增加而向高波数发生位移;在低波数区域,在424, 576和658 cm-1附近的吸收峰位的波数与Na/Na+Ca比值存在很好的线性相关,相关系数依次为R2₁=0.944 2,R2₂=0.928 3,R2₃=0.909 7。采用红外光谱测试技术结合所建立的线性模型可以推断未知翡翠样品的Na/Na+Ca的摩尔比例,当翡翠样品的Na/Na+Ca比值等于0.8时,红外吸收峰应该在658.7, 574.5, 422.5 cm-1处;如果翡翠样品的红外吸收峰波数＜658.7,＜574.5 cm-1,＜422.5 cm-1,则翡翠样品的Na/Na+Ca比值小于0.8,为绿辉石质翡翠;如果翡翠样品的红外吸收峰波数＞658.7,＞574.5,＞422.5 cm-1,则翡翠样品的Na/Na+Ca比值大于0.8,为硬玉质翡翠。该工作为红外光谱技术测量翡翠样品,分析翡翠化学成分,确定翡翠矿物种属提供了一种快捷、省时、方便的无损测量分析方法。     

Passive and temporally continuous optical spectral analyzer of RF signals via wavelength coding

A novel approach realizing an optical spectrum analyzer for photonic detection of an unknown RF carrier signals is presented. The described module may be part of an electronic warfare system in which detection of a narrow band RF signal is required. Moreover, The RF signal is characterized by an unknown time varying carrier frequency embedded in wide band noise. The system uses a passive, fiber based photonic configuration. It allows the spectrum mapping of an incoming electronic RF signal modulated on an optical carrier. The spectral analyzer configuration uses a finite impulse response (FIR) filter that is realized by two different optical paths of parallel fibers which generate a spectral notch filter. Hence, a wavelength coding is realized by chromatic dispersion such that each wavelength is filtered by a different FIR filter. Therefore, the energy at a WDM demux output channels is actually proportional to the spectrum of the input RF signal. This spectral mapping is obtained without lose of temporal RF information.     

AC发泡剂中一种助发泡剂的鉴定

目前国内外通过在AC发泡剂中添加各种促进剂进而获得改性AC的方法已成为一种趋势。添加何种改性剂无疑是研究改性AC的关键。因此定性分析AC中的改性剂,对改性AC的研发将有极大的帮助。文章应用由作者在Vibrational Spectroscopy上首次提出的薄层色谱显微傅里叶红外联用的方法,鉴定出某改性AC中一种罕见添加剂的官能团,结合元素分析及化学物性分析等,推测出此添加剂的结构。通过对推测物质碎裂机理的解释和未知添加剂质谱图的分析,进一部验证了该添加剂为所推测的物质。这种鉴定方法同样适用于AC中其他无标准图谱的改性剂分析。     

茶叶的1H NMR指纹图谱研究

用¹H NMR分析测定35种从福建、云南、广州、江西等地采集及购买的不同种类的茶叶.检测出约20种物质,包括多种氨基酸、茶氨酸、多种儿茶素(表没食子儿茶素(EGC)、表儿茶素(EC)、表没食子儿茶素没食子酸酯（EGCG）、表儿茶素没食子酸酯（ECG）和一些未知的儿茶素)、蔗糖、未知糖类、脂肪酸、 咖啡因等.所得谱图经主成分分析,实现了不同种类的茶叶以及铁观音产地的区分,并且发现了引起区分的化学成分：红茶和黑茶与绿茶和乌龙茶相比,部分氨基酸和一些未知成分的含量较高,而儿茶素的含量较低;安溪西坪铁观音与安溪祥华和感德铁观音相比,部分氨基酸、咖啡因、EGCG、ECG以及一些未知成分的含量较高,而EC、EGC含量相对低.另外,谱图的聚类分析也显示了与主成分分析类似的结果.     

基于质心迭代估计的无线传感器网络节点定位算法

针对无线传感器网络非测距定位方法的应用,提出了基于质心迭代估计的节点定位算法.该算法首先计算当前连通信标节点所围成的平面质心的坐标及其与未知节点间的接收信号强度,然后用计算所得质心节点替代距离未知节点最远的连通信标节点,缩小连通信标节点所围成的平面,并通过多次迭代的方法提高节点定位精度.仿真实验结果表明,该算法的各项指标均为良好,适用于无线传感器网络的节点定位.     

A study on the electrical property of HgSe under high pressure

Using a microcircuit fabricated on a diamond anvil cell, we have measured in-situ conductivity of HgSe under high pressures, and investigated the temperature dependence of conductivity under several different pressures. The result shows that HgSe has a pressure-induced transition sequence from a semimetal to a semiconductor to a metal, similar to that in HgTe. Several discontinuous changes in conductivity are observed at around 1.5, 17, 29 and 49GPa, corresponding to the phase transitions from zinc-blende to cinnabar to rocksalt to orthorhombic to an unknown structure, respectively. In comparison with HgTe, it is speculated that the unknown structure may be a distorted CsCl structure. For the cinnabar-HgSe, the energy gap as a function of pressure is obtained according to the temperature dependence of conductivity. The plot of the temperature dependence of conductivity indicates that the unknown structure of HgSe has an electrical property of a conductor.     

Classification of inhomogeneous media in tomography based on their contrast

The classification of pairs of different substances in accordance with the degree of tomographic visibility of the interfaces between these substances is considered. The classification is performed without using tomographic information and can be considered as a prediction of the quality of the subsequent reconstruction of an unknown medium. The study is based on the solution of the problem of x-ray tomography aimed at the determination of the inner structure of an unknown medium by radiation probing. The classification involves finding the contrast coefficient and studying the character of its energy dependence. The results are illustrated by plots and tomograms obtained by computer simulation.     

基于拉曼光谱的食用植物油快速鉴别

提出了一种基于拉曼光谱的食用植物油快速鉴别方法。基于已知类别的食用植物油样本进行建模,首先对原始拉曼谱图进行基线校正和标准归一化等预处理,并选取食用油不饱和度特征的两处拉曼峰值作为特征向量,计算训练样本特征空间上各个植物油类别的中心坐标;然后,将食用植物油测试样本的拉曼谱图经过相同预处理和特征提取,获取测试样本的特征向量,计算其与各类别中心坐标的欧式距离,根据类中心最小距离法,取欧式距离最小的那一类作为预测样本的类别。针对7类43个食用植物油样本的实验结果表明,采用食用油不饱和度两点描述法进行特征提取,各类别样本聚集效果比PCA好,类间距更大。上述鉴别方法可以准确地实现食用植物油品种的快速分类。     

Backstepping synchronization of uncertain chaotic systems by a single driving variable

In this paper a parameter observer and a synchronization controller are designed to synchronize unknown chaotic systems with diverse structures. Based on stability theory the structures of the observer and the controller are presented. The unknown Coullet system and Rossler system are taken for examples to demonstrate that the method is effective and feasible. The artificial simulation results show that global synchronization between the unknown Coullet system and the Rossler system can be achieved by a single driving variable with co-operation of the observer and the controller, and all parameters of the Coullet system can be identified at the same time.     

An inverse algorithm for reconstructing the acoustic parameters of layered medium

I.IntroductionThcinvcrsescattcringprob1cmisbasicinarcassuchasradar,sonar,geophysica1explora-honandnondestructivctesting.Whenthescatteringobjectisaconstitutiveparametersvaryinacontinuousmannerandtheinvcrseproblcmistodctcrmineoneormoreoftheseparametcrsfromtheobserveddata.Muchofthcpreviousworkonthisproblcmforthecaseofp1anewaveatnormalincidencchasconsistcdofderivingaSchr6dingerequationfromthebasicacousticandstrcss-straincquations,andthenreconstruchngthepotentialappearinginthisequationbyusingtheGe…     

通过幺正操作传送未知两个三能级粒子纠缠态

我们提出一个把未知的两个三能级粒子纠缠态传送给两个接收者的方案,该方案使用一个未知的五个三能级粒子纠缠态作为量子通道。必须指出该方案能够推广到传送未知的N个三能级粒子纠缠态给M个接收者的情况,使用的是未知(N.M 1)个三能级粒子纠缠态作为量子通道。在传送过程中,需要执行适当的幺正操作和(N.M 1)次独立测量,而且该方案不涉及Bell态测量。     

Stabilizing oxide layers on iron particles

Pyrophoric iron powders at different stages of stabilization by oxygen (0–8% by weight) were annealed at 255 or 500°C up to 571 h. During this procedure the magnetic moments first decreased by some per cent and then increased above the initial values. The shape of the magnetic moment versus oxygen uptake curves remained unchanged. The increase of the magnetic moments as a function of time is correlated with a decrease of the specific surface area of the powders. The Mössbauer spectrum of partially stabilized powders is different from that observed on completely stabilized powders and shows a hitherto unknown magnetic iron oxide while X-ray investigations suggest this oxide to be a special iron deficient Fe₃O₄ (spinel) containing vacancies on the octahedral sites distributed at random. The spins in the oxide should then be coupled in an antiparallel way to the underlying iron core in order to explain the measured magnetic moments.     

Is it possible to determine the type of fastening of a vibrating plate from its sounding?

The problem of determining the type of fastening of a circular plate inaccessible to direct observation from the natural frequencies of its symmetric flexural vibrations is considered. The uniqueness theorem for the solution to this inverse problem is proved, and a method for the reconstruction of unknown boundary conditions is indicated. An approximate formula for the determination of unknown boundary conditions from three natural frequencies is obtained. It is assumed that the natural frequencies can be given approximately, within a certain accuracy. The method of an approximate calculation of unknown boundary conditions is illustrated by four examples of different cases of the plate fastening (a free support, an elastic fixing, a floating fixing, and a free edge).     

Probabilistic Teleportation of Two-Particle State of General Formation

A scheme for probabilistic teleporting an unknown two-particle state of general formation by partly pure entangled four-particle state is proposed. It is shown that after performing two Bell state measurements, proper unitary transformation and the measurement on an auxiliary qubit, the unknown two-particle state of general formation, which was destroyed at one place, can be reconstructed at another place with certain probability.     

Approximate Teleportation of an Unknown Atomic-Entangled State with Dissipative Atom-Cavity Resonant Jaynes-Cummings Model

We propose a scheme for approximately and conditionally teleporting an unknown atomic-entangled state in dissipative cavity QED. It is the further development of the scheme of [Phys. Rev. A 69 (2004) 064302], where the cavity mode decay has not been considered and the state teleportated is an unknown atomic state. In this paper, we investigate the influence of the decay on the approximate and conditional teleportation of the unknown atomic-entangled state, which is different from that teleportated in [Phys. Rev. A 69 (2004) 064302] and then give the fidelity of the teleportation, which depends on the cavity mode decay. The scheme may be generalized to not only the teleportation of the cavity-mode-entangled-state by means of a single atom but also the teleportation of the unknown trapped-ion-entangled-state in a linear ion trap.     

基于HIRFL-CSR测量丰中子重核质量的建议

丰中子重核区有大量原子核质量未知,迫切需要实验测量。我们建议,利用兰州重离子加速器研究装置HIRFL-CSR上的等时性质谱术,高精度测量204Pt等丰中子重核的质量。CSR质量测量实验中,在目标核产额尽可能高的前提下,需要每次注入都有多个离子同时储存到实验环CSRe中,才能针对逐次注入修正磁场晃动的影响,得到高精度测量结果。但在丰中子核区,当目标核产生截面非常低时,每次注入能储存到环中的离子数目太少。为了解决这个问题,我们提出了一种"混合厚度靶"的方法,在不明显改变目标核产额的情况下,显著增加同时储存在CSRe中的离子数,满足实验要求。模拟计算表明,在CSRe测量丰中子重核质量是可行的,并推荐了实验的设置。     

Lower bounds on cross sections without unknown constants and valid at all energies

We obtain lower bounds for cross sections (total and differential) which are of the form of integral constraints, and which contain no unknown constants and that are valid at finite energies (and not only asymptotically). The information that we use to obtain the bounds may be of three different types (giving three different kinds of bounds): a few low energy parameters; a few low energy parameters plus experimental information on a given wave (the D wave); or one unphysical parameter that may be obtained from other sources (field theoretical calculations with soft pion techniques). The comparison of the bounds with experiment is also discussed.