The physical fundamentals and influences upon electrode materials' open-circuit voltage (OCV) and the spatial distribution of electrochemical potential in the full cell are briefly reviewed. We hope to illustrate that a better understanding of these scientific problems can help to develop and design high voltage cathodes and interfaces with low Ohmic drop. OCV is one of the main indices to evaluate the performance of lithium ion batteries (LIBs), and the enhancement of OCV shows promise as a way to increase the energy density. Besides, the severe potential drop at the interfaces indicates high resistance there, which is one of the key factors limiting power density.
ISSN: 2058-3834
Chinese Physics B is an international journal covering the latest developments and achievements in all branches of physics (with the exception of nuclear physics and physics of elementary particles and fields, which is covered by Chinese Physics C).
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Zi-Yi Chen et al 2023 Chinese Phys. B 32 118104
The prediction of chemical synthesis pathways plays a pivotal role in materials science research. Challenges, such as the complexity of synthesis pathways and the lack of comprehensive datasets, currently hinder our ability to predict these chemical processes accurately. However, recent advancements in generative artificial intelligence (GAI), including automated text generation and question–answering systems, coupled with fine-tuning techniques, have facilitated the deployment of large-scale AI models tailored to specific domains. In this study, we harness the power of the LLaMA2-7B model and enhance it through a learning process that incorporates 13878 pieces of structured material knowledge data. This specialized AI model, named MatChat, focuses on predicting inorganic material synthesis pathways. MatChat exhibits remarkable proficiency in generating and reasoning with knowledge in materials science. Although MatChat requires further refinement to meet the diverse material design needs, this research undeniably highlights its impressive reasoning capabilities and innovative potential in materials science. MatChat is now accessible online and open for use, with both the model and its application framework available as open source. This study establishes a robust foundation for collaborative innovation in the integration of generative AI in materials science.
Chen Fang et al 2016 Chinese Phys. B 25 117106
We review the recent, mainly theoretical, progress in the study of topological nodal line semimetals in three dimensions. In these semimetals, the conduction and the valence bands cross each other along a one-dimensional curve in the three-dimensional Brillouin zone, and any perturbation that preserves a certain symmetry group (generated by either spatial symmetries or time-reversal symmetry) cannot remove this crossing line and open a full direct gap between the two bands. The nodal line(s) is hence topologically protected by the symmetry group, and can be associated with a topological invariant. In this review, (i) we enumerate the symmetry groups that may protect a topological nodal line; (ii) we write down the explicit form of the topological invariant for each of these symmetry groups in terms of the wave functions on the Fermi surface, establishing a topological classification; (iii) for certain classes, we review the proposals for the realization of these semimetals in real materials; (iv) we discuss different scenarios that when the protecting symmetry is broken, how a topological nodal line semimetal becomes Weyl semimetals, Dirac semimetals, and other topological phases; and (v) we discuss the possible physical effects accessible to experimental probes in these materials.
Limin Cang et al 2022 Chinese Phys. B 31 038402
The emerging perovskite solar cells have been recognized as one of the most promising new-generation photovoltaic technologies owing to their potential of high efficiency and low production cost. However, the current perovskite solar cells suffer from some obstacles such as non-radiative charge recombination, mismatched absorption, light induced degradation for the further improvement of the power conversion efficiency and operational stability towards practical application. The rare-earth elements have been recently employed to effectively overcome these drawbacks according to their unique photophysical properties. Herein, the recent progress of the application of rare-earth ions and their functions in perovskite solar cells were systematically reviewed. As it was revealed that the rare-earth ions can be coupled with both charge transport metal oxides and photosensitive perovskites to regulate the thin film formation, and the rare-earth ions are embedded either substitutionally into the crystal lattices to adjust the optoelectronic properties and phase structure, or interstitially at grain boundaries and surface for effective defect passivation. In addition, the reversible oxidation and reduction potential of rare-earth ions can prevent the reduction and oxidation of the targeted materials. Moreover, owing to the presence of numerous energetic transition orbits, the rare-earth elements can convert low-energy infrared photons or high-energy ultraviolet photons into perovskite responsive visible light, to extend spectral response range and avoid high-energy light damage. Therefore, the incorporation of rare-earth elements into the perovskite solar cells have demonstrated promising potentials to simultaneously boost the device efficiency and stability.
Xiaoling Wu et al 2021 Chinese Phys. B 30 020305
Quantum information processing based on Rydberg atoms emerged as a promising direction two decades ago. Recent experimental and theoretical progresses have shined exciting light on this avenue. In this concise review, we will briefly introduce the basics of Rydberg atoms and their recent applications in associated areas of neutral atom quantum computation and simulation. We shall also include related discussions on quantum optics with Rydberg atomic ensembles, which are increasingly used to explore quantum computation and quantum simulation with photons.
Min Hong et al 2018 Chinese Phys. B 27 048403
Thermoelectric materials, enabling the directing conversion between heat and electricity, are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels. Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature. Due to the intensive theoretical investigations and experimental demonstrations, significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials. In this review, we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties. On this basis, we studied the effect of material parameters on thermoelectric properties. Then, we analyzed the features of Bi2Te3-based thermoelectric materials, including the lattice defects, anisotropic behavior and the strong bipolar conduction at relatively high temperature. Then we accordingly summarized the strategies for enhancing the thermoelectric performance, including point defect engineering, texture alignment, and band gap enlargement. Moreover, we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method, ball milling, and melt spinning. Lastly, we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3, which will enlighten the enhancement of thermoelectric performance in broader materials
Dong-Liang Yang et al 2019 Chinese Phys. B 28 036201
The structural phase transitions of bismuth under rapid compression has been investigated in a dynamic diamond anvil cell using time-resolved synchrotron x-ray diffraction. As the pressure increases, the transformations from phase I, to phase II, to phase III, and then to phase V have been observed under different compression rates at 300 K. Compared with static compression results, no new phase transition sequence appears under rapid compression at compression rate from 0.20 GPa/s to 183.8 GPa/s. However, during the process across the transition from phase III to phase V, the volume fraction of product phase as a function of pressure can be well fitted by a compression-rate-dependent sigmoidal curve. The resulting parameters indicate that the activation energy related to this phase transition, as well as the onset transition pressure, shows a compression-rate-dependent performance. A strong dependence of over-pressurization on compression rate occurs under rapid compression. A formula for over-pressure has been proposed, which can be used to quantify the over-pressurization.
Yan Zhao et al 2018 Chinese Phys. B 27 127806
The perovskite photodetectors can be used for image sensing, environmental monitoring, optical communication, and chemical/biological detection. In the recent five years, the perovskite photoelectric detectors with various devices are well-designed and have made unprecedented progress of light detection. It is necessary to emphasize the most interesting works and summarize them to provide researchers with systematic information. In this review, we report the recent progress in perovskite photodetectors, including highly sensitive, ultrafast response speed, high gain, low noise, flexibility, and narrowband, concentrating on the photodetection performance of versatile halide perovskites (organic–inorganic hybrid and all inorganic compositions). Currently, organic–inorganic hybrid and all-inorganic halide microcrystals with polycrystalline film, nanoparticle/wire/chip, and block monocrystalline morphology control show important performance in response rate, decomposition rate, noise equivalent power, linear dynamic range, and response speed. It is expected that a comprehensive compendium of the research status of perovskite photodetectors will contribute to the development of this area.
Jingyuan Zhong et al 2023 Chinese Phys. B 32 047203
The planar Hall effect (PHE), which originates from anisotropic magnetoresistance, presents a qualitative and simple approach to characterize electronic structures of quantum materials by applying an in-plane rotating magnetic field to induce identical oscillations in both longitudinal and transverse resistances. In this review, we focus on the recent research on the PHE in various quantum materials, including ferromagnetic materials, topological insulators, Weyl semimetals, and orbital anisotropic matters. Firstly, we briefly introduce the family of Hall effect and give a basic deduction of PHE formula with the second-order resistance tensor, showing the mechanism of the characteristic π-period oscillation in trigonometric function form with a π/4 phase delay between the longitudinal and transverse resistances. Then, we will introduce the four main mechanisms to realize PHE in quantum materials. After that, the origin of the anomalous planar Hall effect (APHE) results, of which the curve shapes deviate from that of PHE, will be reviewed and discussed. Finally, the challenges and prospects for this field of study are discussed.
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Saleem Nasir et al 2024 Chinese Phys. B 33 050204
Hybrid nanofluids are remarkable functioning liquids that are intended to reduce the energy loss while maximizing the heat transmission. In the involvement of suction and nonlinear thermal radiation effects, this study attempted to explore the energy transmission features of the inclined magnetohydrodynamic (MHD) stagnation flow of CNTs-hybrid nanofluid across the nonlinear permeable stretching or shrinking sheet. This work also included some noteworthy features like chemical reactions, variable molecular diffusivity, quadratic convection, viscous dissipation, velocity slip and heat omission assessment. Employing appropriate similarity components, the model equations were modified to ODEs and computed by using the HAM technique. The impact of various relevant flow characteristics on movement, heat and concentration profiles was investigated and plotted on a graph. Considering various model factors, the significance of drag friction, heat and mass transfer rate were also computed in tabular and graphical form. This leads to the conclusion that such factors have a considerable impact on the dynamics of fluid as well as other engineering measurements of interest. Furthermore, viscous forces are dominated by increasing the values of λp, δm and δq, and as a result, F'(ξ) accelerates while the opposite trend is observed for M and ϕ. The drag friction is boosted by the augmentation M, λp and ϕ, but the rate of heat transfer declined. According to our findings, hybrid nanoliquid effects dominate that of ordinary nanofluid in terms of F'(ξ), Θ(ξ) and ϕ(ξ) profiles. The HAM and the numerical technique (shooting method) were found to be in good agreement.
Ling-Ling Xing et al 2024 Chinese Phys. B 33 050304
Einstein–Podolsky–Rosen (EPR) steering is an example of nontrivial quantum nonlocality and characteristic in the non-classical world. The directivity (or asymmetry) is a fascinating trait of EPR steering, and it is different from other quantum nonlocalities. Here, we consider the strategy in which two atoms compose a two-qubit X state, and the two atoms are owned by Alice and Bob, respectively. The atom of Alice suffers from a reservoir, and the atom of Bob couples with a bit flip channel. The influences of auxiliary qubits on EPR steering and its directions are revealed by means of the entropy uncertainty relation. The results indicate that EPR steering declines with growing time t when adding fewer auxiliary qubits. The EPR steering behaves as damped oscillation when introducing more auxiliary qubits in the strong coupling regime. In the weak coupling regime, the EPR steering monotonously decreases as t increases when coupling auxiliary qubits. The increases in auxiliary qubits are responsible for the fact that the steerability from Alice to Bob (or from Bob to Alice) can be more effectively revealed. Notably, the introductions of more auxiliary qubits can change the situation that steerability from Alice to Bob is certain to a situation in which steerability from Bob to Alice is certain.
Yi Liu et al 2024 Chinese Phys. B 33 057401
We report the physical properties of ThRu3Si2 featured with distorted Ru kagome lattice. The combined experiments of resistivity, magnetization and specific heat reveal bulk superconductivity with Tc = 3.8 K. The specific heat jump and calculated electron–phonon coupling indicate a moderate coupled BCS superconductor. In comparison with LaRu3Si2, the calculated electronic structure in ThRu3Si2 shows an electron-doping effect with electron filling lifted from 100 meV below flat bands to 300 meV above it. This explains the lower superconducting transition temperature and weaker electron correlations observed in ThRu3Si2. Our work suggests the Tc and electronic correlations in the kagome superconductor could have an intimate connection with the flat bands.
Licun Fu et al 2024 Chinese Phys. B 33 056401
One hallmark of glasses is the existence of excess vibrational modes at low frequencies ω beyond Debye's prediction. Numerous studies suggest that understanding low-frequency excess vibrations could help gain insight into the anomalous mechanical and thermodynamic properties of glasses. However, there is still intensive debate as to the frequency dependence of the population of low-frequency excess vibrations. In particular, excess modes could hybridize with phonon-like modes and the density of hybridized excess modes has been reported to follow Dexc(ω) ∼ ω2 in 2D glasses with an inverse power law potential. Yet, the universality of the quadratic scaling remains unknown, since recent work suggested that interaction potentials could influence the scaling of the vibrational spectrum. Here, we extend the universality of the quadratic scaling for hybridized excess modes in 2D to glasses with potentials ranging from the purely repulsive soft-core interaction to the hard-core one with both repulsion and attraction as well as to glasses with significant differences in density or interparticle repulsion. Moreover, we observe that the number of hybridized excess modes exhibits a decrease in glasses with higher density or steeper interparticle repulsion, which is accompanied by a suppression of the strength of the sound attenuation. Our results indicate that the density bears some resemblance to the repulsive steepness of the interaction in influencing low-frequency properties.
Zhi-Hao Yang and Yan-Long Yang 2024 Chinese Phys. B 33 050203
In evolutionary games, most studies on finite populations have focused on a single updating mechanism. However, given the differences in individual cognition, individuals may change their strategies according to different updating mechanisms. For this reason, we consider two different aspiration-driven updating mechanisms in structured populations: satisfied-stay unsatisfied shift (SSUS) and satisfied-cooperate unsatisfied defect (SCUD). To simulate the game player's learning process, this paper improves the particle swarm optimization algorithm, which will be used to simulate the game player's strategy selection, i.e., population particle swarm optimization (PPSO) algorithms. We find that in the prisoner's dilemma, the conditions that SSUS facilitates the evolution of cooperation do not enable cooperation to emerge. In contrast, SCUD conditions that promote the evolution of cooperation enable cooperation to emerge. In addition, the invasion of SCUD individuals helps promote cooperation among SSUS individuals. Simulated by the PPSO algorithm, the theoretical approximation results are found to be consistent with the trend of change in the simulation results.
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Kai Ren et al 2024 Chinese Phys. B 33 057202
Since the superior mechanical, chemical and physical properties of high-entropy alloys (HEAs) were discovered, they have gradually become new emerging candidates for renewable energy applications. This review presents the novel applications of HEAs in thermoelectric energy conversion. Firstly, the basic concepts and structural properties of HEAs are introduced. Then, we discuss a number of promising thermoelectric materials based on HEAs. Finally, the conclusion and outlook are presented. This article presents an advanced understanding of the thermoelectric properties of HEAs, which provides new opportunities for promoting their applications in renewable energy.
Hongxin Chen et al 2024 Chinese Phys. B 33 047304
The anomalous valley Hall effect (AVHE) can be used to explore and utilize valley degrees of freedom in materials, which has potential applications in fields such as information storage, quantum computing and optoelectronics. AVHE exists in two-dimensional (2D) materials possessing valley polarization (VP), and such 2D materials usually belong to the hexagonal honeycomb lattice. Therefore, it is necessary to achieve valleytronic materials with VP that are more readily to be synthesized and applicated experimentally. In this topical review, we introduce recent developments on realizing VP as well as AVHE through different methods, i.e., doping transition metal atoms, building ferrovalley heterostructures and searching for ferrovalley materials. Moreover, 2D ferrovalley systems under external modulation are also discussed. 2D valleytronic materials with AVHE demonstrate excellent performance and potential applications, which offer the possibility of realizing novel low-energy-consuming devices, facilitating further development of device technology, realizing miniaturization and enhancing functionality of them.
Qiwen Qu et al 2024 Chinese Phys. B 33 047803
Besides the diverse investigations on the interactions between intense laser fields and molecular systems, extensive research has been recently dedicated to exploring the response of nanosystems excited by well-tailored femtosecond laser fields. Due to the fact that nanostructures hold peculiar effects when illuminated by laser pulses, the underlying mechanisms and the corresponding potential applications can make significant improvements in both fundamental research and development of novel techniques. In this review, we provide a summarization of the strong field ionization occurring on the surface of nanosystems. The molecules attached to the nanoparticle surface perform as the precursor in the ionization and excitation of the whole nanosystem, the fundamental processes of which are yet to be discovered. We discuss the influence on nanoparticle constituents, geometric shapes and sizes, as well as the specific waveforms of the excitation laser fields. The intriguing characteristics observed in surface ion emission reflect how enhanced near field affects the localized ionizations and nanoplasma expansions, thereby paving the way for further precision controls on the light-and-matter interactions in the extreme spatial temporal levels.
Yubo Yang et al 2024 Chinese Phys. B 33 030702
AI development has brought great success to upgrading the information age. At the same time, the large-scale artificial neural network for building AI systems is thirsty for computing power, which is barely satisfied by the conventional computing hardware. In the post-Moore era, the increase in computing power brought about by the size reduction of CMOS in very large-scale integrated circuits (VLSIC) is challenging to meet the growing demand for AI computing power. To address the issue, technical approaches like neuromorphic computing attract great attention because of their feature of breaking Von-Neumann architecture, and dealing with AI algorithms much more parallelly and energy efficiently. Inspired by the human neural network architecture, neuromorphic computing hardware is brought to life based on novel artificial neurons constructed by new materials or devices. Although it is relatively difficult to deploy a training process in the neuromorphic architecture like spiking neural network (SNN), the development in this field has incubated promising technologies like in-sensor computing, which brings new opportunities for multidisciplinary research, including the field of optoelectronic materials and devices, artificial neural networks, and microelectronics integration technology. The vision chips based on the architectures could reduce unnecessary data transfer and realize fast and energy-efficient visual cognitive processing. This paper reviews firstly the architectures and algorithms of SNN, and artificial neuron devices supporting neuromorphic computing, then the recent progress of in-sensor computing vision chips, which all will promote the development of AI.
Yanan Dai 2024 Chinese Phys. B 33 038703
Exploring the realms of physics that extend beyond thermal equilibrium has emerged as a crucial branch of condensed matter physics research. It aims to unravel the intricate processes involving the excitations, interactions, and annihilations of quasi- and many-body particles, and ultimately to achieve the manipulation and engineering of exotic non-equilibrium quantum phases on the ultrasmall and ultrafast spatiotemporal scales. Given the inherent complexities arising from many-body dynamics, it therefore seeks a technique that has efficient and diverse detection degrees of freedom to study the underlying physics. By combining high-power femtosecond lasers with real- or momentum-space photoemission electron microscopy (PEEM), imaging excited state phenomena from multiple perspectives, including time, real space, energy, momentum, and spin, can be conveniently achieved, making it a unique technique in studying physics out of equilibrium. In this context, we overview the working principle and technical advances of the PEEM apparatus and the related laser systems, and survey key excited-state phenomena probed through this surface-sensitive methodology, including the ultrafast dynamics of electrons, excitons, plasmons, spins, etc., in materials ranging from bulk and nano-structured metals and semiconductors to low-dimensional quantum materials. Through this review, one can further envision that time-resolved PEEM will open new avenues for investigating a variety of classical and quantum phenomena in a multidimensional parameter space, offering unprecedented and comprehensive insights into important questions in the field of condensed matter physics.
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You Zou et al 2019 Chinese Phys. B 28 035203
We have investigated the flux symmetry on the capsule in a six-cylinder-port hohlraum for improving the design of the hohlraum. The influence factors of drive symmetry on the capsule in the hohlraum are studied, including laser power, laser beams arrangement, hohlraum geometric parameters, plasma condition, capsule convergence, etc. The x-ray radiation flux distribution on the capsule is obtained based on the three-dimensional view factor model. In the six-cylinder-port hohlraum, the main drive asymmetry is the C40 mode asymmetry. When the C40 mode asymmetry approaches zero, the drive symmetry on the capsule is optimal. Our results demonstrate that in order to have a high flux symmetry on the capsule in the laser main-pulse stage, more negative initial C40 modes are needed, which can be realized by adjusting the hohlraum geometry parameters. The hohlraum with column length LH = 4.81 mm has an optimal symmetry in the laser main-pulse stage.
Dong-Liang Yang et al 2019 Chinese Phys. B 28 036201
The structural phase transitions of bismuth under rapid compression has been investigated in a dynamic diamond anvil cell using time-resolved synchrotron x-ray diffraction. As the pressure increases, the transformations from phase I, to phase II, to phase III, and then to phase V have been observed under different compression rates at 300 K. Compared with static compression results, no new phase transition sequence appears under rapid compression at compression rate from 0.20 GPa/s to 183.8 GPa/s. However, during the process across the transition from phase III to phase V, the volume fraction of product phase as a function of pressure can be well fitted by a compression-rate-dependent sigmoidal curve. The resulting parameters indicate that the activation energy related to this phase transition, as well as the onset transition pressure, shows a compression-rate-dependent performance. A strong dependence of over-pressurization on compression rate occurs under rapid compression. A formula for over-pressure has been proposed, which can be used to quantify the over-pressurization.
Bin-Bin Fu et al 2019 Chinese Phys. B 28 037103
Topological Dirac semimetals (DSMs) present a kind of topologically nontrivial quantum state of matter, which has massless Dirac fermions in the bulk and topologically protected states on certain surfaces. In superconducting DSMs, the effects of their nontrivial topology on superconducting pairing could realize topological superconductivity in the bulk or on the surface. As superconducting pairing takes place at the Fermi level EF, to make the effects possible, the Dirac points should lie in the vicinity of EF so that the topological electronic states can participate in the superconducting paring. Here, we show using angle-resolved photoelectron spectroscopy that in a series of (Ir1−xPtx)Te2 compounds, the type-II Dirac points reside around EF in the superconducting region, in which the bulk superconductivity has a maximum Tc of ∼ 3 K. The realization of the coexistence of bulk superconductivity and low-energy Dirac fermions in (Ir1−xPtx)Te2 paves the way for studying the effects of the nontrivial topology in DSMs on the superconducting state.
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Zhang et al
In this work, the dependences of spin wave resonance (SWR) frequency on the surface anisotropy field, interface exchange coupling, symmetry, biquadratic exchange (BQE) interaction, film thickness and the external magnetic field in bilayer ferromagnetic films have been theoretically analyzed by employing the linear spin wave approximation and Green's function method. A remarkable increase of SWR frequency, except for energetically lower two modes, can be obtained in our model that takes into account the BQE interaction. Again, the effect of the external magnetic field on SWR frequency can be increased by increasing the biquadratic to interlayer exchange ratio. It has been identified that the BQE interaction is of utmost importance in improving the SWR frequency of the bilayer ferromagnetic films. In addition, for bilayer ferromagnetic films, the frequency gap between the energetically highest mode and lowest mode is found to increase with increasing the biquadratic to interlayer exchange ratio and film thickness, and with destroying the symmetry of the system. These results can be used to improve the understanding of magnetic properties in bilayer ferromagnetic films and thus may have prominent implications for future magnetic devices.
Xu et al
The quantitative relationship between nanosecond pulsed laser parameters and the characteristics of laser-generated ultrasonic waves in polycrystalline materials was evaluated. The high energy of the pulsed laser with a large irradiation spot simultaneously generated ultrasonic longitudinal and shear waves at the epicenter under the slight ablation regime. An optimized denoising technique based on wavelet thresholding and variational mode decomposition was applied to reduce noise in shear waves with a low signal-to-noise ratio. An approach for characterizing grain size was proposed using spectral center frequency ratio (SCFR) based on time-frequency analysis. The results have demonstrated that the generation regime of ultrasonic waves is not solely determined by the laser power density; even at high power densities, a high energy with a large spot can generate an ultrasonic waveform dominated by the thermoelastic effect. It is ascribed to the intensification of the thermoelastic effect with the proportional increase in laser irradiation spot area for a given laser power density. Furthermore, both longitudinal and shear wave SCFRs are linearly related to grain size in polycrystalline materials; however, the shear wave SCFR is more sensitive to finer-grained materials. This study holds great significance for evaluating metal material properties using laser ultrasound.
Wang
In this work, we develop universal quantum computing models that form a family of quantum von Neumann architectures, with modular units of memory, control, CPU, and internet, besides input and output. This family contains three generations characterized by dynamical quantum resource theory, and it also circumvents no-go theorems on quantum programming and control. Besides universality, such a family satisfies other desirable engineering requirements on system and algorithm design, such as modularity and programmability, hence serves as a unique approach to build universal quantum computers.
Li et al
In this paper, we present a qubit-loss-free(QLF) fusion scheme for generating large-scale atom W states in cavity quantum electrodynamics(QED) system. Compared to the most current fusion schemes which are conditioned on the case where one particle can be extracted from each initial W state to fusion process, our scheme will access one or two particles from each W state. Based on the atom-cavity-field detuned interaction, three |W>n+m+t states can be generated from |W>n, |W>m and |W>t state with the help of two auxiliary atoms, three |W>n+m+t+q states can be generated from |W>n, |W>m, |W>t and a |W>q state with the help of three auxiliary atoms. Comparing the numerical simulations of the resource cost of fusing three small-size W states based on the precious schemes with those based ours, our fusion scheme seems more efficient. This QLF fusion scheme can be generalized to the case of fusing k different or inentical particles W states. Furthermore, with no qubit loss, it greatly reduces the number of fusion steps and prepare W states with larger particle numbers.
Shang et al
We investigate the topological properties of a two-chain quantum ladder with uneven legs, i.e. the two chains differ in their periods by a factor of two. Such an uneven ladder presents rich band structures classified by the closure of either direct or indirect bandgaps. It also provides opportunities to explore fundamental concepts concerning band topology and edge modes, including the difference of intracellular and intercellular Zak phases, and the role of the inversion symmetry (IS). We calculate the Zak phases of the two kinds and find excellent agreement with the dipole moment and extra charge accumulation, respectively. We also find that configurations with IS feature a pair of degenerate two-side edge modes emerging as the closure of the direct bandgap, while configurations without IS feature one-side edge modes emerging as not only the closure of both direct and indirect bandgap but also within the band continuum. Furthermore, by projecting to the two sublattices, we find that the effective Bloch Hamiltonian corresponds to that of a generalized Su-Schrieffer-Heeger model or Rice-Mele model whose hopping amplitudes depend on the quasimomentum. In this way, the topological phases can be efficiently extracted through winding numbers. We propose that uneven ladders can be realized by spin-dependent optical lattices and their rich topological characteristics can be examined by near future experiments.