Quantum correlations for bipartite continuous-variable systems

Two quantum correlations Q and \(Q_\mathcal P\) for \((m+n)\)-mode continuous-variable systems are introduced in terms of average distance between the reduced states under the local Gaussian positive operator-valued measurements, and analytical formulas of these quantum correlations for bipartite Gaussian states are provided. It is shown that the product states do not contain these quantum correlations, and conversely, all \((m+n)\)-mode Gaussian states with zero quantum correlations are product states. Generally, \(Q\ge Q_{\mathcal P}\), but for the symmetric two-mode squeezed thermal states, these quantum correlations are the same and a computable formula is given. In addition, Q is compared with Gaussian geometric discord for symmetric squeezed thermal states.     

考虑负相关性信息的协同过滤算法研究

为了研究Pearson负相关性信息对协同过滤算法的影响, 提出了一种考虑负相关性信息的协同过滤算法。该算法选取正相关用户作为最近邻居, 负相关用户作为最远邻居, 使用参数调节最近邻居和最远邻居在推荐过程中的作用。MovieLens数据集上的对比实验表明, 负相关性不仅可以提高推荐结果的准确性, 而且可以增加推荐列表的多样性; 进一步分析发现, 负相关性还可以大幅度提高不活跃用户的推荐准确性。该工作表明, 负相关性有助于解决推荐系统中准确性、多样性两难的问题和冷启动问题。     

Quantum correlations of identical particles subject to classical environmental noise

In this work, we propose a measure for the quantum discord of indistinguishable particles, based on the definition of entanglement of particles given in Wiseman and Vaccaro (Phys Rev Lett 91:097902, 2003. doi: 10.1103/PhysRevLett.91.097902). This discord of particles is then used to evaluate the quantum correlations in a system of two identical bosons (fermions), where the particles perform a quantum random walk described by the Hubbard Hamiltonian in a 1D lattice. The dynamics of the particles is either unperturbed or subject to a classical environmental noise—such as random telegraph, pink or brown noise. The observed results are consistent with those for the entanglement of particles, and we observe that on-site interaction between particles have an important protective effect on correlations against the decoherence of the system.     

Quantum correlations in a family of bipartite separable qubit states

Quantum correlations (QCs) in some separable states have been proposed as a key resource for certain quantum communication tasks and quantum computational models without entanglement. In this paper, a family of nine-parameter separable states, obtained from arbitrary mixture of two sets of bi-qubit product pure states, is considered. QCs in these separable states are studied analytically or numerically using four QC quantifiers, i.e., measurement-induced disturbance (Luo in Phys Rev A77:022301, 2008), ameliorated MID (Girolami et al. in J Phys A Math Theor 44:352002, 2011),quantum dissonance (DN) (Modi et al. in Phys Rev Lett 104:080501, 2010), and new quantum dissonance (Rulli in Phys Rev A 84:042109, 2011), respectively. First, an inherent symmetry in the concerned separable states is revealed, that is, any nine-parameter separable states concerned in this paper can be transformed to a three-parameter kernel state via some certain local unitary operation. Then, four different QC expressions are concretely derived with the four QC quantifiers. Furthermore, some comparative studies of the QCs are presented, discussed and analyzed, and some distinct features about them are exposed. We find that, in the framework of all the four QC quantifiers, the more mixed the original two pure product states, the bigger QCs the separable states own. Our results reveal some intrinsic features of QCs in separable systems in quantum information.     

Easily simulated multivariate binary distributions with given positive and negative correlations

We consider the problem of defining a multivariate distribution of binary variables, with given first two moments, from which values can be easily simulated. Oman and Zucker [Oman, S.D., Zucker, D.M., 2001. Modelling and generating correlated binary variables. Biometrika 88, 287-290] have done this when the correlation matrix of the binary variables is the Schur product of a parametric correlation matrix appropriate for normal variables (intraclass, moving average or autoregressive), having non-negative entries, with a matrix whose entries comprise the Fréchet upper bounds on the pairwise correlations of the binary variables. We extend their method to include negative correlations; moreover, we extend the range of positive correlations allowed in the moving-average case. We present algorithms for simulation of data from these distributions, and examine the ranges of correlations obtained.     

Quantum correlations generation and distribution in a universal covariant quantum cloning circuit

We discussed the distribution and generation of quantum correlations in a universal covariant quantum cloning circuit. Specifically, we first considered the distribution of quantum correlation, i.e., quantum discord, among the four qubits of the circuit. Then, we analyzed the generation of genuine 3- or 4-qubit entanglement in the cloning process. It is found that the circuit generates genuine 4-qubit GHZ (Greenberger-Horne-Zeilinger)-type state while only W-type 3-qubit state could be generated. These results illustrate the special quantum correlation manipulation capabilities of the cloning circuit.     

LCDs for use at low temperatures

Despite the widespread use of liquid crystals their performance is constrained by their poor low temperature response. This problem can be avoided simply by heating the display.     

Quantum correlations responsible for remote state creation: strong and weak control parameters

We study the quantum correlations between the two remote qubits (sender and receiver) connected by the transmission line (homogeneous spin-1/2 chain) depending on the parameters of the sender’s and receiver’s initial states (control parameters). We consider two different measures of quantum correlations: the entanglement (a traditional measure) and the informational correlation (based on the parameter exchange between the sender and receiver). We find the domain in the control parameter space yielding (i) zero entanglement between the sender and receiver during the whole evolution period and (ii) non-vanishing informational correlation between the sender and receiver, thus showing that the informational correlation is responsible for the remote state creation. Among the control parameters, there are the strong parameters (which strongly effect the values of studied measures) and the weak ones (whose effect is negligible), therewith the eigenvalues of the initial state are given a privileged role. We also show that the problem of small entanglement (concurrence) in quantum information processing is similar (in certain sense) to the problem of small determinants in linear algebra. A particular model of 40-node spin-1/2 communication line is presented.     

Quantum correlations in Gaussian states via Gaussian channels: steering,entanglement, and discord

Here we study the quantum steering, quantum entanglement, and quantum discord for Gaussian Einstein–Podolsky–Rosen states via Gaussian channels. And the sudden death phenomena for Gaussian steering and Gaussian entanglement are theoretically observed. We find that some Gaussian states have only one-way steering, which confirms the asymmetry of quantum steering. Also we investigate that the entangled Gaussian states without Gaussian steering and correlated Gaussian states own no Gaussian entanglement. Meanwhile, our results support the assumption that quantum entanglement is intermediate between quantum discord and quantum steering. Furthermore, we give experimental recipes for preparing quantum states with desired types of quantum correlations.     

Scatter search-based identification of local patterns with positive and negative correlations in gene expression data

This paper presents a scatter search approach based on linear correlations among genes to find biclusters, which include both shifting and scaling patterns and negatively correlated patterns contrarily to most of correlation-based algorithms published in the literature. The methodology established here for comparison is based on a priori biological information stored in the well-known repository Gene Ontology (GO). In particular, the three existing categories in GO, Biological Process, Cellular Components and Molecular Function, have been used. The performance of the proposed algorithm has been compared to other benchmark biclustering algorithms, specifically a group of classical biclustering algorithms and two algorithms that use correlation-based merit functions. The proposed algorithm outperforms the benchmark algorithms and finds patterns based on negative correlations. Although these patterns contain important relationship among genes, they are not found by most of biclustering algorithms. The experimental study also shows the importance of the size in a bicluster in addition to the value of its correlation. In particular, the size of a bicluster has an influence over its enrichment in a GO term.     

基于时空联合的解码边信息插值算法

在Wyner-Ziv视频编码中,边信息质量是影响系统编码效率的关键因素,但解码端获得的运动矢量不精确而导致内插边信息的质量不高。为此,提出一种基于时空联合的解码边信息插值算法。该算法将多种块分割模式与双向运动估计相结合,匹配准则采用双向平均绝对误差和(SBAD)判断运动矢量时间变化,利用边界绝对误差(BAD)判断运动矢量的空间变化,通过时空联合匹配准则保证运动矢量的空间平滑性和时间连贯性。实验结果表明,该算法降低了编码码率,内插边信息的主观和客观质量均有所提高,边信息的峰值信噪比(PSNR)最大提高1.41dB。     

A Quantum Monte Carlo method at fixed energy

In this paper we explore ways to study the zero temperature limit of quantum statistical mechanics using Quantum Monte Carlo simulations. We develop a Quantum Monte Carlo method in which one fixes the ground state energy as a parameter. The Hamiltonians we consider are of the form H=H₀+λV with ground state energy E. For fixed H₀ and V, one can view E as a function of λ whereas we view λ as a function of E. We fix E and define a path integral Quantum Monte Carlo method in which a path makes no reference to the times (discrete or continuous) at which transitions occur between states. For fixed E we can determine λ(E) and other ground state properties of H.     

昆腾携StorNext5亮相BIRTV

昆腾将携 StorNext5参加即将在中国国际展览中心的北京国际广播电影电视设备展览会（BIRTV2014）。BIRTV是由国家新闻出版广电总局主办，中国中央电视台承办的。自1987年创办至今，已成为当前中国最权威的广播电影电视专业设备综合展览会。在此次展会上，昆腾将通过先进的技术，与强氧科技等各界合作伙伴紧密合作，与用户共同面对未来发展的全新视角。     

茄尼醇萃取结晶提纯的实验及关联研究

茄尼醇(Sol)是一种不饱和的聚异戊二烯醇,属四倍半萜醇,具有较强的抗癌生物活性。由于茄尼醇的粘度很大、熔点低,无法用传统的方法分离纯化,针对其分离难问题,本文提出采用乙酸乙酯为萃取溶剂,甲醇为结晶溶剂,利用两级萃取结晶装置分离提纯茄尼醇。实验数据用最小方差法进行关联,用NEWTON-LAPUSON法进行迭代,实验及关联的结果表明5g茄尼醇粗品和20 mL乙酸乙酯充分混合均匀后,在30 mL甲醇中结晶,控制结晶温度为54℃,抽滤时间为40 min,可得到60%以上的茄尼醇粗品,本文工作为进一步试验研究提供了依据。     

Ambient temperatures preferred by young European males and females at rest

Forty-eight young adults (24 men and 24 women) stayed for three hours in a climatic chamber setting, lightly clothed and seated at rest with no prescribed task; rectal and mean skin temperatures were continuously recorded. During the first hour, the subjects were exposed to an imposed ambient temperature (25.1 degrees C) during which body temperatures stabilized and subjective thermal judgments were collected. For the next two hours they could freely set the ambient temperature at the level(s) they preferred. The subjects spent about one hour seeking a preferred temperature (transition period), which subsequently turned out to be unsteady in most cases. The overall mean of the individual average preferred temperatures (third hour) was 26.6 degrees C (S.D. = 2.6 degrees C). Significant time of day (morning versus afternoon) effects were found on preferred ambient and actual body temperatures. The body temperatures previously recorded at 25.1 degrees C were significantly predictive of the average ambient temperatures preferred between one and two hours later (third hour); the multiple regression equations differed markedly between men and women.     

Mechanical property characterization of LPCVD silicon nitride thin films at cryogenic temperatures

T-shape, LPCVD silicon nitride cantilevers are fabricated to determine Young's modulus and fracture strength of silicon nitride thin films at room and cryogenic temperatures. A helium-cooled measurement setup is developed and installed inside a focused-ion-beam (FIB) system. A lead-zirconate-titanate (PZT) translator powered by a function generator and a dc voltage is utilized as an actuator, and a silicon diode is used as a temperature sensor in this setup. Resonant frequencies of identical cantilevers with different "milling masses" are measured to obtain thickness and Young's modulus of the silicon nitride thin films, while a bending test is performed to obtain fracture strength. From the experiment, the average Young's modulus of low-pressure chemical-vapor deposition (LPCVD) silicon nitride thin films varies from 260.5 GPa at room temperature (298 K) to 266.6 GPa at 30 K, and the average fracture strength ranges from 6.9 GPa at room temperature to 7.9 GPa at 30 K. The measurement setup and technique presented here can be used to characterize the mechanical properties of different MEMS materials at cryogenic temperatures.     

Application of aeroelastic modes on nonlinear supersonic panel flutter at elevated temperatures

This paper shows that the use of aeroelastic modes, instead of the traditional in vacuo natural modes, can reduce drastically the number of coupled nonlinear modal equations for the large amplitude nonlinear panel flutter analysis at an arbitrary yawed supersonic flow angle and elevated temperatures. All four types of panel behavior can be predicted and they are flat and stable, aerothermally buckled but dynamically stable, limit cycle oscillations, and chaos.