查看更多>>摘要：The non-Hermitian skin effect and edge burst reflect the vital role of spatial boundaries in non-Hermitian systems from both static and dynamic perspectives.In this study,we investigate a non-Hermitian dissipative lattice with nonlocal coupling and demonstrate many interesting static and dynamic phenomena.In the case of global coupling with all sites coupled with each other,we observe anomalous hopping resonance,where a quantum walker initially placed at a single site almost completely escapes from the boundary of the system regardless of its initial position.In the case of non-global coupling,which is infinite-range coupling,the interplay between nonlocal hopping and the non-Hermitian skin effect results in the emergence of local bulk modes exhibiting a multipartite density distribution.The presence of local bulk modes induces the nontrivial dynamics of a quantum walker,which features multiple peaks of lost probability in spatially separated domains.Our findings demonstrate unique properties induced by nonlocal coupling in non-Hermitian systems.
查看更多>>摘要：Open quantum system simulations are essential for exploring novel quantum phenomena and evaluating noisy quantum circuits.In this Letter,we investigate whether mixed states generated from noisy quantum circuits can be efficiently represented by locally purified density operators(LPDOs).We map an LPDO of N qubits to a pure state of size 2 × N defined on a ladder and introduce a unified method for managing virtual and Kraus bonds.We numerically simulate noisy random quantum circuits with depths of up to d=40 using fidelity and entanglement entropy as accuracy measures.The LPDO representation is effective in describing mixed states in both the quantum and classical regions;however,it encounters significant challenges at the quantum-classical critical point,restricting its applicability to the quantum region.In contrast,matrix product operators(MPO)successfully characterize the entanglement trend throughout the simulation,while the truncation in MPOs breaks the positivity condition required for a physical density matrix.This work advances our understanding of efficient mixed-state representations in open quantum systems and provides insights into the entanglement structure of noisy quantum circuits.
查看更多>>摘要：Optical solitons in mode-locked fiber lasers and optical communication links have various applications.The study of transmission modes of optical solitons necessitates the investigation of the relationship between the equation parameters and soliton evolution employing deep learning techniques.However,the existing identifica-tion models exhibit a limited parameter domain search range and are significantly influenced by initialization.Consequently,they often result in divergence toward incorrect parameter values.This study harnessed reinforce-ment learning to revamp the iterative process of the parameter identification model.By developing a two-stage optimization strategy,the model could conduct an accurate parameter search across arbitrary domains.The investigation involved several experiments on various standard and higher-order equations,illustrating that the innovative model overcame the impact of initialization on the parameter search,and the identified parameters are guided toward their correct values.The enhanced model markedly improves the experimental efficiency and holds significant promise for advancing the research of soliton propagation dynamics and addressing intricate scenarios.
查看更多>>摘要：Phase transitions are both thermodynamically and quantum-mechanically ubiquitous in nature and laborato-ries,and their understanding remains one of the most active issues in modern physics and related disciplines.The Landau theory provides a general framework to describe phenomenologically phase transitions by introducing order parameters and associated symmetry breaking.This theory is also taken as a starting point to explore critical phenomena in connection with phase transitions in the renormalization group,which provides a complete theoretical description of behaviors close to critical points.In this context,the microscopic mechanism of phase transitions remains unclear.In this study,we explore the microscopic mechanism of the superradiant phase tran-sition in the quantum Rabi model(QRM).First,we perform a diagonalization operation in an operator space to obtain three fundamental patterns,denoted as λ1,λ2,and λ3,involved in the QRM.Then,we explicitly analyze the energy evolutions of these patterns with increasing coupling strength.The observed characteristic behaviors reveal the microscopic mechanism of the superradiant phase transition as a consequence of competition between patterns due to different phase relations.In other words,with increasing coupling strength,the pattern λ1 drives the phase transition,the pattern λ2 exhibits a similar response speed but less energy compensation than the pattern λ1,and the pattern λ3 exhibits a slow response speed but plays a key role in the balance between it and the pattern λ1,which stabilizes the new phase.This type of dissecting mechanism explains why and how the superradiant phase transition occurs in the QRM and paves the way for exploring the microscopic mechanism of phase transitions that occur frequently in nature.
查看更多>>摘要：The interpretation of representations and generalization powers has been a long-standing challenge in the fields of machine learning(ML)and artificial intelligence.This study contributes to understanding the emergence of universal scaling laws in quantum-probabilistic ML.We consider the generative tensor network(GTN)in the form of a matrix-product state as an example and show that with an untrained GTN(such as a random TN state),the negative logarithmic likelihood(NLL)L generally increases linearly with the number of features M,that is,L～kM+const.This is a consequence of the so-called"catastrophe of orthogonality,"which states that quantum many-body states tend to become exponentially orthogonal to each other as M increases.This study reveals that,while gaining information through training,the linear-scaling law is suppressed by a negative quadratic correction,leading to L(～)βM-αM2+const.The scaling coefficients exhibit logarithmic relationships with the number of training samples and quantum channels The emergence of a quadratic correction term in the NLL for the testing(training)set can be regarded as evidence of the generalization(representation)power of the GTN.Over-parameterization can be identified by the deviation in the values of α between the training and testing sets while increasing x.We further investigate how orthogonality in the quantum-feature map relates to the satisfaction of quantum-probabilistic interpretation and the representation and generalization powers of the GTN.Unveiling universal scaling laws in quantum-probabilistic ML would be a valuable step toward establishing a white-box ML scheme interpreted within the quantum-probabilistic framework.
查看更多>>摘要：Recently,a new method has been proposed to compute parton distributions using boosted correlators fixed in the Coulomb gauge(CG)within the framework of large-momentum effective theory.This approach,which does not involve Wilson lines,could greatly improve the efficiency and precision of lattice quantum chromodynamics calculations.However,concerns remain regarding whether systematic uncertainties from Gribov copies,which correspond to ambiguities in lattice gauge-fixing,are adequately controlled.This work assesses the effects of Gribov copies on Coulomb-gauge-fixed quark correlators.We utilize different strategies for Coulomb-gauge fixing,selecting two different groups of Gribov copies based on lattice gauge configurations.We examine the differences in the resulting spatial quark correlators in both vacuum and pion states.Our findings indicate that the statistical errors of the matrix elements from both Gribov copies,regardless of the correlation range,decrease proportionally to the square root of the number of gauge configurations.The difference between the strategies does not show statistical significance compared to the gauge noise,demonstrating that the effect of the Gribov copies can be neglected in practical lattice calculations of quark parton distributions.
查看更多>>摘要：Parton distribution functions(DFs)have long been recognized as key measures of hadron structure.Today,theoretical prediction of such DFs is becoming possible using diverse methods for continuum and lattice analyses of strong interaction(QCD)matrix elements.Recent developments include a demonstration that continuum and lattice analyses yield mutually consistent results for all pion DFs,with behavior on the far valence domain of light-front momentum fraction that matches QCD expectations.Theory is also delivering an understanding of the distributions of proton mass and spin amongst its constituents,which varies,of course,with the resolving scale of the measuring probe.Aspects of the pion DF and proton spin developments are sketched herein,along with some novel perspectives on gluon and quark orbital angular momentum.
查看更多>>摘要：Terahertz(THz)circular dichroism(TCD)spectroscopy is extensively used to examine the chiral properties of biological macromolecules and other materials.The rapid advancements in strong-field THz generation and field-modulated techniques highlights the importance of advancing tunable strong-field TCD spectroscopy technology.In this study,we designed and implemented an integrated strong-field TCD spectroscopy system.By using a tilted-pulse-front technique,we generated linearly polarized strong-field THz radiation and achieved linear-to-circular polarization conversion via a reflective metasurface.The resulting circularly polarized THz radiation exhibited an ellipticity greater than 0.9 in the frequency range of 0.38-0.61 THz,achieving a linear-to-circular conversion efficiency exceeding 90％.Additionally,the peak electric field strength of the circularly polarized THz radiation exceeded 100kV/cm.The proposed system is expected to be instrumental in investigating the chiral characteristics of materials under strong field conditions and in examining how these characteristics vary under different field conditions.
查看更多>>摘要：A two-stage training method is proposed to enhance imaging quality and reduce reconstruction time in data-driven single-pixel imaging(SPI)under undersampling conditions.This approach leverages a deep learning algorithm to simulate single-pixel detection and image reconstruction.During the initial training stage,an L2 regularization constraint is imposed on convolution modulation patterns to determine the optimal initial network weights.In the subsequent stage,a coupled deep learning method integrating coded-aperture design and SPI is adopted,which utilizes backpropagation of the loss function to iteratively optimize both the binarized modulation patterns and imaging network parameters.By reducing the binarization errors introduced by the dithering algorithm,this approach improves the quality of data-driven SPI.Compared with traditional deep-learning SPI methods,the proposed method significantly reduces computational complexity,resulting in accelerated image reconstruction.Experimental and simulation results demonstrate the advantages of the method,including high imaging quality,short image reconstruction time,and simplified training.For an image size of 64 x 64 pixels and 10％sampling rate,the proposed method achieves a peak signal-to-noise ratio of 23.22 dB,structural similarity index of 0.76,and image reconstruction time of approximately 2.57 x 10-4 seconds.
查看更多>>摘要：Advancements in orbital angular momentum(OAM)mode-multiplexing communication networks require tunable mode filters for selective channel demultiplexing and downloading.In this study,we propose a spatial depth-dependent mode transformation strategy for the tunable filtering of OAM modes.By integrating the spi-ral phase and lens phase modulations,we achieved mode conversions that varied with the transmission depth,enabling selective demultiplexing in predetermined axial planes.This approach facilitates tunable mode filtering by adjusting spatial depths.As a proof of concept,we fabricated a mode filter using two-photon polymeriza-tion lithography(TPL)technology,successfully filtering five OAM modes with mode crosstalk below-10.9dB.Additionally,the filter was applied in a mode-multiplexing communication link,achieving tunable demultiplex-ing of five mode channels with bit error rates below 10-6.These results highlight the efficacy and flexibility of our strategy for OAM mode filtering and offer promising insights for the development of mode-multiplexing communication networks and channel interconnections.
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