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Experimental Validation of Quantum Steering Ellipsoids and Tests of Volume Monogamy Relations

Physical Review Letters 2019年第7期122卷 070402-070402页

作者： Chao Zhang Shuming Cheng Li Li Qiu-Yue Liang Bi-Heng Liu Yun-Feng Huang Chuan-Feng Li Guang-Can Guo Michael J. W. Hall Howard M. Wiseman Geoff J. Pryde Key Laboratory of Quantum Information University of Science and Technology of China CAS Hefei 230026 People’s Republic of China CAS Center For Excellence in Quantum Information and Quantum Physics University of Science and Technology of China Hefei 230026 People’s Republic of China Centre for Quantum Computation and Communication Technology (Australian Research Council) Centre for Quantum Dynamics Griffith University Brisbane QLD 4111 Australia

The set of all qubit states that can be steered to by measurements on a correlated qubit is predicted to form an ellipsoid—called the quantum steering ellipsoid—in the Bloch ball. This ellipsoid provides a simple visual characterization of the initial two-qubit state, and various aspects of entanglement are reflected in its geometric properties. We experimentally verify these properties via measurements on many different polarization-entangled photonic qubit states. Moreover, for pure three-qubit states, the volumes of the two quantum steering ellipsoids generated by measurements on the first qubit are predicted to satisfy a tight monogamy relation, which is strictly stronger than the well-known monogamy of entanglement for concurrence. We experimentally verify these predictions, using polarization and path entanglement. We also show experimentally that this monogamy relation can be violated by a mixed entangled state, which nevertheless satisfies a weaker monogamy relation.

关键词： Nonlocality Quantum correlations in quantum information Quantum optics

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Charged lepton flavor violation in the B−L symmetric SSM

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Physical Review D 2024年第5期109卷 055019-055019页

作者： Xing-Xing Dong Shu-Min Zhao Jia-Peng Huo Tong-Tong Wang Tai-Fu Feng College of Physics Science and Technology Hebei University Baoding 071002 China Hebei Key Laboratory of High-precision Computation and Application of Quantum Field Theory Baoding 071002 China Hebei Research Center of the Basic Discipline for Computational Physics Baoding 071002 China Department of Physics Chongqing University Chongqing 401331 China

Charged lepton flavor violation (CLFV) represents a clear new physics (NP) signal beyond the standard model (SM). In this work, we investigate CLFV processes lj−→li−γ utilizing mass insertion approximation (MIA) in the minimal supersymmetric extension of the SM with local B−L gauge symmetry (B−L SSM). The MIA method can provide a set of simple analytic formulas for the form factors and the associated effective vertices, so that the movement of the CLFV decays lj−→li−γ with the sensitive parameters will be intuitively analyzed. Considering the SM-like Higgs boson mass and the muon anomalous dipole moment (MDM) within 4σ, 3σ, and 2σ regions, we discuss the corresponding constraints on the relevant parameter space of the model.

关键词： Supersymmetric models Leptons Flavor symmetries Magnetic moment

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Differentiable programming tensor networks for Kitaev magnets

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Physical Review B 2023年第8期108卷 085103-085103页

作者： Xing-Yu Zhang Shuang Liang Hai-Jun Liao Wei Li Lei Wang Institute of Physics Chinese Academy of Sciences Beijing 100190 China Department of Physics University of Science and Technology of China Beijing 100080 China Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China Institute of Theoretical Physics Chinese Academy of Sciences Beijing 100190 China CAS Center for Excellence in Topological Quantum Computation Chinese Academy of Sciences Beijing 100190 China

We present a general computational framework to investigate ground-state properties of quantum spin models on infinite two-dimensional lattices using automatic differentiation-based gradient optimization of infinite projected entangled-pair states. The approach exploits the variational uniform matrix product states to contract infinite tensor networks with unit cell structure and incorporates automatic differentiation to optimize the local tensors. We applied this framework to the Kitaev-type model, which involves complex interactions and competing ground states. To evaluate the accuracy of this method, we compared the results with exact solutions for the Kitaev model and found that it has a better agreement for various observables compared to previous tensor network calculations based on imaginary-time projection. Additionally, by finding out the ground state with lower variational energy compared to previous studies, we provided convincing evidence for the existence of nematic paramagnetic phases and 18-site configuration in the phase diagram of the K−Γ model. Furthermore, in the case of the realistic K−J−Γ−Γ′ model for the Kitaev material α−RuCl3, we discovered a noncollinear zigzag ground state. Lastly, we also find that the strength of the critical out-of-plane magnetic field that suppresses such a zigzag state has a lower transition field value than the previous finite-cylinder calculations. The framework is versatile and will be useful for a quick scan of phase diagrams for a broad class of quantum spin models.

关键词： Approximation methods for many-body systems Kitaev model Lattice models in condensed matter Machine learning Many-body techniques Tensor network methods

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Exterior optical cloaking and illusions by using active sources: A boundary element perspective

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Physical Review B 2010年第19期81卷 195116-195116页

作者： H. H. Zheng J. J. Xiao Y. Lai C. T. Chan Department of Physics and William Mong Institute of NanoScience and Technology The Hong Kong University of Science and Technology Clear Water Bay Hong Kong China Department of Electronic and Information Engineering and Key Laboratory of Network Oriented Intelligent Computation Shenzhen Graduate School Harbin Institute of Technology Shenzhen 518055 China

Recently, it was demonstrated that active sources can be used to cloak any objects that lie outside the cloaking devices [F. Guevara Vasquez, G. W. Milton, and D. Onofrei, Phys. Rev. Lett. 103, 073901 (2009)]. Here, we propose that active sources can create illusion effects so that an object outside the cloaking device can be made to look like another object. Invisibility is a special case in which the concealed object is transformed to a volume of air. From a boundary element perspective, we show that active sources can create a nearly “silent” domain which can conceal any objects inside and at the same time make the whole system look like an illusion of our choice outside a virtual boundary. The boundary element method gives the fields and field gradients, which can be related to monopoles and dipoles, on continuous curves which define the boundary of the active devices. Both the cloaking and illusion effects are confirmed by numerical simulations.

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Automated Detection of Epileptic Spikes and Seizures Incorporating a Novel Spatial Clustering Prior

Automated Detection of Epileptic Spikes and Seizures Incorpo...

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2024 IEEE International Conference on Bioinformatics and Biomedicine, BIBM 2024

作者： Dong, Hanyang Sheng, Shurong Wang, Xiongfei Gao, Jia-Hong Sun, Yi Yang, Wanli Xiao, Kuntao Teng, Pengfei Luan, Guoming Lv, Zhao Anhui University School of Artificial Intelligence Hefei230601 China Hefei Comprehensive National Science Center Anhui Province Key Laboratory of Biomedical Imaging and Intelligent Processing Institute of Artificial Intelligence Hefei230088 China Sanbo Brain Hospital Capital Medical University Beijing Key Laboratory of Epilepsy Department of Neurosurgery Beijing China Peking University McGovern Institute for Brain Research Beijing China Peking University Center for Mri Research Academy for Advanced Interdisciplinary Studies Beijing China Peking University Beijing City Key Lab for Medical Physics and Engineering Institute of Heavy Ion Physics School of Physics Beijing China Anhui University Anhui Province Key Laboratory of Multimodal Cognitive Computation School of Computer Science and Technology Hefei230601 China

ISBN: (纸本)9798350386226

A Magnetoencephalography (MEG) time-series recording consists of multi-channel signals collected by superconducting sensors, with each signal's intensity reflecting magnetic field changes over time at the sensor location. Automating epileptic MEG spike detection significantly reduces manual assessment time and effort, yielding substantial clinical benefits. Existing research addresses MEG spike detection by encoding neural network inputs with signals from all channel within a time segment, followed by classification. However, these methods overlook simultaneous spiking occurred from nearby sensors. We introduce a simple yet effective paradigm that first clusters MEG channels based on their sensor's spatial position. Next, a novel convolutional input module is designed to integrate the spatial clustering and temporal changes of the signals. This module is fed into a custom MEEG-ResNet3D developed by the authors, which learns to extract relevant features and classify the input as a spike clip or not. Our method achieves an F1 score of 94.73% on a large real-world MEG dataset Sanbo-CMR collected from two centers, outperforming state-of-the-art approaches by 1.85%. Moreover, it demonstrates efficacy and stability in the Electroencephalographic (EEG) seizure detection task, yielding an improved weighted F1 score of 1.4% compared to current state-of-the-art techniques evaluated on TUSZ, whch is the largest EEG seizure dataset. © 2024 IEEE.

关键词： Magnetoencephalography

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Dual fermion method for disordered electronic systems

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Physical Review B 2013年第13期87卷 134208-134208页

作者： H. Terletska S.-X. Yang Z. Y. Meng J. Moreno M. Jarrell Condensed Matter Physics and Materials Science Department Brookhaven National Laboratory Upton New York 11973 USA Department of Physics and Astronomy Louisiana State University Baton Rouge Louisiana 70803 USA Center for Computation and Technology Louisiana State University Baton Rouge Louisiana 70803 USA

While the coherent potential approximation (CPA) is the prevalent method for the study of disordered electronic systems, it fails to capture nonlocal correlations and Anderson localization. To incorporate such effects, we extend the dual fermion approach to disordered systems using the replica method. The developed method utilizes the exact mapping to the dual fermion variables, and includes intersite scattering via diagrammatic perturbation theory in the dual variables. The CPA is recovered as a zeroth-order approximation. Results for single- and two-particle quantities show good agreement with a cluster extension of the CPA; moreover, weak localization is captured. As a natural extension of the CPA, our method presents an alternative to existing nonlocal cluster theories for disordered systems, and has potential applications in the study of disordered systems with electronic interactions.

关键词： ELECTRONIC systems ANDERSON localization FERMIONS PARTICLES (Nuclear physics) CONDENSED matter

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Statistical inference for community detection in signed networks

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Physical Review E 2017年第4期95卷 042313-042313页

作者： Xuehua Zhao Bo Yang Xueyan Liu Huiling Chen School of Digital Media Shenzhen Institute of Information Technology Shenzhen 518172 China Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University Changchun 130012 China College of Computer Science and Technology Jilin University Changchun 130012 China College of Physics and Electronic Information Wenzhou University Wenzhou 325035 China

The problem of community detection in networks has received wide attention and proves to be computationally challenging. In recent years, with the surge of signed networks with positive links and negative links, to find community structure in such signed networks has become a research focus in the area of network science. Although many methods have been proposed to address the problem, their performance seriously depends on the predefined optimization objectives or heuristics which are usually difficult to accurately describe the intrinsic structure of community. In this study, we present a statistical inference method for community detection in signed networks, in which a probabilistic model is proposed to model signed networks and the expectation-maximization–based parameter estimation method is deduced to find communities in signed networks. In addition, to efficiently analyze signed networks without any a priori information, a model selection criterion is also proposed to automatically determine the number of communities. In our experiments, the proposed method is tested in the synthetic and real-word signed networks and compared with current methods. The experimental results show the proposed method can more efficiently and accurately find the communities in signed networks than current methods. Notably, the proposed method is a mathematically principled method.

关键词： Clustering Community structure Stochastic inference

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High rectifying performance of heterojunctions with interface between armchair C3N nanoribbons with and without edge H-passivation

arXiv

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arXiv 2022年

作者： Zhang, Jie Ding, Wence Li, Xiaobo Zhou, Guanghui Hunan Normal University Changsha410081 China Department of Applied Physics School of Science Key Laboratory of Hunan Province for Statistical Learning and Intelligent Computation Hunan University of Technology and Business Changsha410205 China

Two-dimensional polyaniline with C3N stoichiometry, is a newly fabricated layered material that has been expected to possess fascinating electronic, thermal, mechanical and chemical properties. The nature of its counterpart nano-ribbons/structures offering even more tunability in property because of the unique quantum confinement and edge effect, however, has not been revealed sufficiently. Here, using the first-principles calculation based on density functional theory and nonequilibrium Green's function technique, we first perform a study on the electron band structure of armchair C3N nanoribbons (AC3NNRs) without and with H-passivation. The calculated results show that the pristine AC3NNRs are metal, while the H-passivated ones are either direct or indirect band gap semiconductors depending on the detailed edge atomic configurations. Then we propose a lateral planar homogenous junction with an interface between the pristine and H-passivated AC3NNRs, in which forms a Schottky-like barrier. Interestingly, our further transport calculation demonstrates that this AC3NNRsbased heterojunction exhibits a good rectification behavior. In specification, the average rectification ratio (RR) can reach up to 103 in the bias regime from 0.2 to 0.4 V. Particularly, extending the length of semiconductor part in the heterojunction leads to the decrease of the current through the junction, but the RR can be enlarged obviously. The average RR increases to the order of 104 in the bias from 0.25 to 0.40 V, with the boosted maximum up to 105 at 0.35 V. The findings of this work may be serviceable for the design of functional nanodevices based on AC3NNRs in the future. Copyright © 2022, The Authors. All rights reserved.

关键词： Nanoribbons

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Decays of Majorana or Andreev Oscillations Induced by Steplike Spin-Orbit Coupling

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Physical Review Letters 2019年第14期122卷 147701-147701页

作者： Zhan Cao Hao Zhang Hai-Feng Lü Wan-Xiu He Hai-Zhou Lu X. C. Xie Shenzhen Institute for Quantum Science and Engineering and Department of Physics Southern University of Science and Technology Shenzhen 518055 China School of Physics Southeast University Nanjing 211189 China Peng Cheng Laboratory Shenzhen 518055 China Shenzhen Key Laboratory of Quantum Science and Engineering Shenzhen 518055 China State Key Laboratory of Low Dimensional Quantum Physics Department of Physics Tsinghua University Beijing 100084 China Beijing Academy of Quantum Information Sciences Beijing 100193 China School of Physics University of Electronic Science and Technology of China Chengdu 610054 China Center for Interdisciplinary Studies and Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Lanzhou University Lanzhou 730000 China International Center for Quantum Materials School of Physics Peking University Beijing 100871 China CAS Center for Excellence in Topological Quantum Computation University of Chinese Academy of Sciences Beijing 100190 China

The Majorana zero mode in the semiconductor-superconductor nanowire is one of the promising candidates for topological quantum computing. Recently, in islands of nanowires, subgap-state energies have been experimentally observed to oscillate as a function of the magnetic field, showing a signature of overlapped Majorana bound states. However, the oscillation amplitude either dies away after an overshoot or decays, sharply opposite to the theoretically predicted enhanced oscillations for Majorana bound states. We reveal that a steplike distribution of spin-orbit coupling in realistic devices can induce the decaying Majorana oscillations, resulting from the coupling-induced energy repulsion between the quasiparticle spectra on the two sides of the step. This steplike spin-orbit coupling can also lead to decaying oscillations in the spectrum of the Andreev bound states. For Coulomb-blockade peaks mediated by the Majorana bound states, the peak spacings have been predicted to correlate with peak heights by a π/2 phase shift, which was ambiguous in recent experiments and may be explained by the steplike spin-orbit coupling. Our work will inspire more works to reexamine effects of the nonuniform spin-orbit coupling, which is generally present in experimental devices.

关键词： Coulomb blockade Majorana fermions Quantum transport Spin-orbit coupling Topological phases of matter Topological superconductors

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Calculating the ρ radiative decay width with lattice QCD 36

Calculating the ρ radiative decay width with lattice QCD

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36th Annual International Symposium on Lattice Field Theory, LATTICE 2018

作者： Leskovec, Luka Alexandrou, Constantia Meinel, Stefan Negele, John W. Paul, Srijit Petschlies, Marcus Pochinsky, Andrew Rendon, Gumaro Syritsyn, Sergey Thomas Jefferson National Accelerator Facility 12000 Jefferson Avenue Newport NewsVA23606 United States Department of Physics University of Cyprus P.O. Box 20537 Nicosia1678 Cyprus Computation-based Science and Technology Research Center Cyprus Institute 20 Kavafi Street Nicosia2121 Cyprus Department of Physics University of Arizona TucsonAZ85721 United States RIKEN BNL Research Center Brookhaven National Laboratory UptonNY11973 United States Center for Theoretical Physics Laboratory for Nuclear Science Department of Physics Massachusetts Institute of Technology CambridgeMA02139 United States Helmholtz-Institut für Strahlen- und Kernphysik Rheinische Friedrich-Wilhelms-Universität Bonn Nußallee 14-16 BonnD-53115 Germany Department of Physics and Astronomy Stony Brook University Stony BrookNY11794 United States

We present the results of our lattice QCD study of the πγ → ππ process, where the ρ resonance appears as an enhancement in the transition amplitude. We use Nf = 2 + 1 clover fermions on a lattice of L = 3.6 fm and a pion mass of 320 MeV. Using a combination of forward, stochastic, and sequential propagators, we calculate the two-point and three-point functions that allow us to determine the πγ → ππ matrix elements for several values of the invariant mass s and momentum transfer q2. To fit the q2 and s dependence of the πγ → ππ amplitude, we explore a set of general parametrizations based on a Taylor expansion. By analytic continuation to the complex pole corresponding to the ρ resonance, we determine the resonant form factors and calculate the radiative decay width of the ρ. © Copyright owned by the author(s) under the terms of the Creative Commons.

关键词： Stochastic systems

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