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Vortex Quantum Droplets under Competing Nonlinearities
Gui-hua Chen, Hong-cheng Wang, Hai-ming Deng, and Boris A. Malomed
Chin. Phys. Lett.    2024, 41 (2): 020501 .   DOI: 10.1088/0256-307X/41/2/020501
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This concise review summarizes recent advancements in theoretical studies of vortex quantum droplets (VQDs) in matter-wave fields. These are robust self-trapped vortical states in two- and three-dimensional (2D and 3D) Bose–Einstein condensates (BECs) with intrinsic nonlinearity. Stability of VQDs is provided by additional nonlinearities resulting from quantum fluctuations around mean-field states, often referred to as the Lee–Huang–Yang (LHY) corrections. The basic models are presented, with emphasis on the interplay between the mean-field nonlinearity, LHY correction, and spatial dimension, which determines the structure and stability of VQDs. We embark by delineating fundamental properties of VQDs in the 3D free space, followed by consideration of their counterparts in the 2D setting. Additionally, we address stabilization of matter-wave VQDs by optical potentials. Finally, we summarize results for the study of VQDs in the single-component BEC of atoms carrying magnetic moments. In that case, the anisotropy of the long-range dipole-dipole interactions endows the VQDs with unique characteristics. The results produced by the theoretical studies in this area directly propose experiments for the observation of novel physical effects in the realm of quantum matter, and suggest potential applications to the design of new schemes for processing classical and quantum information.
Tunable Three-Wavelength Fiber Laser and Transient Switching between Three-Wavelength Soliton and Q-Switched Mode-Locked States
Zhi-Zeng Si, Chao-Qing Dai, and Wei Liu
Chin. Phys. Lett.    2024, 41 (2): 020502 .   DOI: 10.1088/0256-307X/41/2/020502
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We report a passive mode-locked fiber laser that can realize single-wavelength tuning and multi-wavelength spacing tuning simultaneously. The tuning range is from 1528 nm–1560 nm, and up to three bands of soliton states can be output at the same time. These results are confirmed by a nonlinear Schrödinger equation model based on the split-step Fourier method. In addition, we reveal a way to transform the multi-wavelength soliton state into the Q-switched mode-locked state, which is period doubling. These results will promote the development of optical communication, optical sensing and multi-signal pulse emission.
Engineering Quantum Criticality for Quantum Dot Power Harvesting
Jin-Yi Wang, Lei-Lei Nian, and Jing-Tao Lü
Chin. Phys. Lett.    2024, 41 (2): 020503 .   DOI: 10.1088/0256-307X/41/2/020503
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Coupling of quantum-dot circuits to microwave photons enables us to investigate photon-assisted quantum transport. Here, we revisit this typical circuit quantum electrodynamical setup by introducing the Kerr nonlinearity of photons. By exploiting quantum critical behavior, we propose a powerful scheme to control the power-harvesting efficiency in the microwave regime, where the driven-dissipative optical system acts as an energy pump. It drives electron transport against a load in the quantum-dot circuit. The energy transfer and, consequently, the harvesting efficiency are enhanced near the critical point. As the critical point moves towards to low input power, high efficiency within experimental parameters is achieved. Our results complement fundamental studies of photon-to-electron conversion at the nanoscale and provide practical guidance for designs of integrated photoelectric devices through quantum criticality.
Experimentally Ruling Out Joint Reality Based on Locality with Device-Independent Steering
Shuaining Zhang, Xiang Zhang, Zhiyue Zheng, and Wei Zhang
Chin. Phys. Lett.    2024, 41 (1): 010301 .   DOI: 10.1088/0256-307X/41/1/010301
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As an essential concept to understand the world, whether the real values (or physical realities) of observables are suitable to physical systems beyond the classic has been debated for many decades. Although standard no-go results based on Bell inequalities have ruled out the joint reality of incompatible quantum observables, the possibility of giving simple yet strong arguments to rule out joint reality in any physical system (not necessarily quantum) with weaker assumptions and less observables has been explored and proposed recently. Here, we perform a device-independent experiment on a two-qubit superconducting system to show that the joint reality of two observables is incompatible with locality under the weaker assumption of the reality of observables in a single space-time region (or single qubit). Our results clearly show the violation of certain inequalities derived from both linear and nonlinear criteria. In addition, we study the robustness of the linear and nonlinear criterion against the effect of systematic decoherence. Our demonstration opens up the possibility of delineating classical and non-classical boundaries with simpler nontrivial quantum system.
Bounding Free Energy Difference with Flow Matching
Lu Zhao and Lei Wang
Chin. Phys. Lett.    2023, 40 (12): 120201 .   DOI: 10.1088/0256-307X/40/12/120201
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We introduce a method for computing the Helmholtz free energy using the flow matching technique. Unlike previous work that utilized flow-based models for variational free energy calculations, this method provides bounds for free energy estimation based on targeted free energy perturbation by performing calculations on samples from both ends of the mapping. We demonstrate applications of the present method by estimating the free energy of a classical Coulomb gas in a harmonic trap.
Multi-Pseudo Peakons in the $b$-Family Fifth-Order Camassa–Holm Model
Dinghao Zhu and Xiaodong Zhu
Chin. Phys. Lett.    2023, 40 (12): 120202 .   DOI: 10.1088/0256-307X/40/12/120202
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The $b$-family fifth-order Camassa–Holm model is a nontrivial extension of the celebrated Camassa–Holm model. This work investigates single-pseudo and multi-pseudo peakon solutions of this model via analytical calculations and numerical simulations. Some intriguing phenomena of multi-pseudo peakon which do not appear in the classical Camassa–Holm model interactions are observed, such as two-pseudo peakon collapses, three-pseudo peakon resonance, and multi-pseudo peakon inelastic collisions. The present work will inspire further studies on the higher-dimensional integrable Camassa–Holm systems which may have high value in investigating the related higher-dimensional physical problems.
Entropy of Regular Black Holes in Einstein's Gravity
Chen Lan and Yan-Gang Miao
Chin. Phys. Lett.    2023, 40 (12): 120401 .   DOI: 10.1088/0256-307X/40/12/120401
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We calculate the entropy of spherically symmetric regular black holes by the path-integral method in Einstein's gravity. This method provides evidence that the entropy of spherically symmetric regular black holes is proportional to a quarter of horizon area, indicating no violation of the entropy-area law.
New Painlevé Integrable (3+1)-Dimensional Combined pKP–BKP Equation: Lump and Multiple Soliton Solutions
Abdul-Majid Wazwaz
Chin. Phys. Lett.    2023, 40 (12): 120501 .   DOI: 10.1088/0256-307X/40/12/120501
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We introduce a new form of the Painlevé integrable (3+1)-dimensional combined potential Kadomtsev–Petviashvili equation incorporating the B-type Kadomtsev–Petviashvili equation (pKP–BKP equation). We perform the Painlevé analysis to emphasize the complete integrability of this new (3+1)-dimensional combined integrable equation. We formally derive multiple soliton solutions via employing the simplified Hirota bilinear method. Moreover, a variety of lump solutions are determined. We also develop two new (3+1)-dimensional pKP–BKP equations via deleting some terms from the original form of the combined pKP–BKP equation. We emphasize the Painlevé integrability of the newly developed equations, where multiple soliton solutions and lump solutions are derived as well. The derived solutions for all examined models are all depicted through Maple software.
Splitting of Degenerate Superatomic Molecular Orbitals Determined by Point Group Symmetry
Rui Wang, Jiarui Li, Zhonghua Liu, Chenxi Wan, and Zhigang Wang
Chin. Phys. Lett.    2023, 40 (11): 110201 .   DOI: 10.1088/0256-307X/40/11/110201
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We first confirm an idea obtained from first-principles calculations, which is in line with symmetry theory: Although superatomic molecular orbitals (SAMOs) can be classified according to their angular momentum similar to atomic orbitals, SAMOs with the same angular momentum split due to the point group symmetry of superatoms. Based on this idea, we develop a method to quantitatively modulate the splitting spacing of molecular orbitals in a superatom by changing its structural symmetry or by altering geometric parameters with the same symmetry through expansion and compression processes. Moreover, the modulation of the position crossover is achieved between the lowest unoccupied molecular orbital and the highest occupied molecular orbital originating from the splitting of different angular momenta, leading to an effective reduction in system energy. This phenomenon is in line with the implication of the Jahn–Teller effect. This work provides insights into understanding and regulating the electronic structures of superatoms.
Wave-Particle Duality via Quantum Fisher Information
Chang Niu and Sixia Yu
Chin. Phys. Lett.    2023, 40 (11): 110301 .   DOI: 10.1088/0256-307X/40/11/110301
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Quantum Fisher information (QFI) plays an important role in quantum metrology, placing the ultimate limit to how precise we can estimate some unknown parameter and thus quantifying how much information we can extract. We observe that both the wave and particle properties within a Mach–Zehnder interferometer can naturally be quantified by QFI. Firstly, the particle property can be quantified by how well one can estimate the a priori probability of the path taken by the particle within the interferometer. Secondly, as the interference pattern is always related to some phase difference, the wave property can be quantified by how well one can estimate the phase parameter of the original state. With QFI as the unified figure of merit for both properties, we propose a more general and stronger wave-particle duality relation than the original one derived by Englert.
Dynamically Characterizing the Structures of Dirac Points via Wave Packets
Dan-Dan Liang, Xin Shen, and Zhi Li
Chin. Phys. Lett.    2023, 40 (11): 110302 .   DOI: 10.1088/0256-307X/40/11/110302
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Topological non-trivial band structures are the core problem in the field of topological materials. We investigate the topological band structure in a system with controllable Dirac points from the perspective of wave packet dynamics. By adding a third-nearest-neighboring coupling to the graphene model, additional pairs of Dirac points emerge. The emergence and annihilation of Dirac points result in hybrid and parabolic points, and we show that these band structures can be revealed by the dynamical behaviors of wave packets. In particular, for the gapped hybrid point, the motion of the wave packet shows a one-dimensional Zitterbewegung motion. Furthermore, we also show that the winding number associated with the Dirac point and parabolic point can be determined via the center of mass and spin texture of wave packets, respectively. The results of this work could motivate new experimental methods to characterize a system's topological signatures through wave packet dynamics, which may also find applications in systems of other exotic topological materials.
Continuous-Variable Quantum Computation in Circuit QED
Xiaozhou Pan, Pengtao Song, and Yvonne Y. Gao
Chin. Phys. Lett.    2023, 40 (11): 110303 .   DOI: 10.1088/0256-307X/40/11/110303
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Global Positioning Scheme via Quantum Teleportation
You-Quan Li, Li-Hua Lu, and Qi-Hang Zhu
Chin. Phys. Lett.    2023, 40 (11): 110304 .   DOI: 10.1088/0256-307X/40/11/110304
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Quantum teleportation scheme is undoubtedly an inspiring theoretical discovery as an amazing application of quantum physics, which was experimentally realized several years later. For the purpose of quantum communication via this scheme, an entangled ancillary pair shared by Alice and Bob is the essential ingredient, and a quantum memory in Bob's system is necessary for him to keep the quantum state until the classical message from Alice arrives. Yet, the quantum memory remains a challenge in both technology and rationale. Here we show that quantum teleportation provides fresh perspectives in terms of an alternative scheme for global positioning system. Referring to fixed locations of Bob and Charlie, Alice can determine her relative position by comparing quantum states before and after teleporting around via Bob and Charlie successively. This may open up a new scene in the stage of the application of quantum physics without quantum memories.
Topological Plasma Transport from a Diffusion View
Zhoufei Liu and Jiping Huang
Chin. Phys. Lett.    2023, 40 (11): 110305 .   DOI: 10.1088/0256-307X/40/11/110305
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Recent studies have identified plasma as a topological material. Yet, these researches often depict plasma as a fluid governed by electromagnetic fields, i.e., a classical wave system. Indeed, plasma transport can be characterized by a unique diffusion process distinguished by its collective behaviors. We adopt a simplified diffusion-migration method to elucidate the topological plasma transport. Drawing parallels to the thermal conduction-convection system, we introduce a double-ring model to investigate the plasma density behaviors in the anti-parity-time reversal (APT) unbroken and broken phases. Subsequently, by augmenting the number of rings, we have established a coupled ring chain structure. This structure serves as a medium for realizing the APT symmetric one-dimensional (1D) reciprocal model, representing the simplest tight-binding model with a trivial topology. To develop a model featuring topological properties, we should modify the APT symmetric 1D reciprocal model from the following two aspects: hopping amplitude and onsite potential. From the hopping amplitude, we incorporate the non-reciprocity to facilitate the non-Hermitian skin effect, an intrinsic non-Hermitian topology. Meanwhile, from the onsite potential, the quasiperiodic modulation has been adopted onto the APT symmetric 1D reciprocal model. This APT symmetric 1D Aubry–André–Harper model is of topological nature. Additionally, we suggest the potential applications for these diffusive plasma topological states. This study establishes a diffusion-based approach to realize topological states in plasma, potentially inspiring further advancements in plasma physics.
Efficiency Bound of Learning with Coarse Graining
Minghao Li, Shihao Xia, Youlin Wang, Minglong Lv, Jincan Chen, and Shanhe Su
Chin. Phys. Lett.    2023, 40 (11): 110501 .   DOI: 10.1088/0256-307X/40/11/110501
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A thermodynamic formalism describing the efficiency of information learning is proposed, which is applicable to stochastic thermodynamic systems with multiple internal degrees of freedom. The learning rate, entropy production rate and entropy flow from the system to the environment under coarse-grained dynamics are derived. The Cauchy–Schwarz inequality is applied to demonstrate the lower bound on the entropy production rate of an internal state. The inequality of the entropy production rate is tighter than the Clausius inequality, leading to a derivative of the upper bound on the efficiency of learning. The results are verified in cellular networks with information processes.
Resonant Scattering of Gravitational Waves with Electromagnetic Waves
Ruodi Yan and Yun Kau Lau
Chin. Phys. Lett.    2023, 40 (10): 100401 .   DOI: 10.1088/0256-307X/40/10/100401
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A certain class of exact solutions of Einstein Maxwell spacetime in general relativity is discussed to demonstrate that at the level of theory, when certain parametric resonance condition is met, the interaction of electromagnetic field with a gravitational wave will display certain Lyapunov instability and lead to exponential amplification of a gravitational wave train described by certain Newman–Penrose component of the Weyl curvature. In some way akin to a free electron laser in electromagnetic theory, by the conversion of electromagnetic energy into gravitational energy in a coherent way, the feasibility of generating a pulsed-laser-like intense beam of gravitational wave is displayed.
Free Energy, Stability, and Particle Source in Dynamical Holography
Yu Tian, Xiao-Ning Wu, and Hongbao Zhang
Chin. Phys. Lett.    2023, 40 (10): 100402 .   DOI: 10.1088/0256-307X/40/10/100402
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We study dynamical holographic systems and the relation between thermodynamical and dynamical stability of such systems, using the conserved currents in the bulk spacetime. In particular, in the probe limit a generalized free energy is defined with the property of monotonic decreasing in dynamic processes. It is then shown that the (absolute) thermodynamical stability implies the dynamical stability, while the linear dynamical stability implies the thermodynamical (meta-)stability. The holographic superfluid is taken as an example to illustrate our general formalism, where the dynamic evolution of the system in contact with a particle source is clarified by theoretical investigation and numerical verification. The case going beyond the probe limit is also discussed.
A Hierarchy in Majorana Non-Abelian Tests and Hidden Variable Models
Peng Qian and Dong E. Liu
Chin. Phys. Lett.    2023, 40 (10): 100501 .   DOI: 10.1088/0256-307X/40/10/100501
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The recent progress of the Majorana experiments paves a way for the future tests of non-Abelian braiding statistics and topologically protected quantum information processing. However, a deficient design in those tests could be very dangerous and reach false-positive conclusions. A careful theoretical analysis is necessary so as to develop loophole-free tests. We introduce a series of classical hidden variable models to capture certain key properties of Majorana system: non-locality, topologically non-triviality, and quantum interference. Those models could help us to classify the Majorana properties and to set up the boundaries and limitations of Majorana non-Abelian tests: fusion tests, braiding tests and test set with joint measurements. We find a hierarchy among those Majorana tests with increasing experimental complexity.
Quantum Brayton Refrigeration Cycle with Finite-Size Bose–Einstein Condensates
Jiehong Yuan, Huilin Ruan, Dehua Liu, Jizhou He, and Jianhui Wang
Chin. Phys. Lett.    2023, 40 (10): 100502 .   DOI: 10.1088/0256-307X/40/10/100502
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We consider a quantum Brayton refrigeration cycle consisting of two isobaric and two adiabatic processes, using an ideal Bose gas of finite particles confined in a harmonic trap as its working substance. Quite generally, such a machine falls into three different cases, classified as the condensed region, non-condensed phase, and regime across the critical point. When the refrigerator works near the critical region, both figure of merit and cooling load are significantly improved due to the singular behavior of the specific heat, and the coefficient of performance at maximum figure of merit is much larger than the Curzon–Ahlborn value. With the machine in the non-condensed regime, the coefficient of performance for maximum figure of merit agrees well with the Curzon–Ahlborn value.
Effective Control of Three Soliton Interactions for the High-Order Nonlinear Schr?dinger Equation
Yanli Yao, Houhui Yi, Xin Zhang, and Guoli Ma
Chin. Phys. Lett.    2023, 40 (10): 100503 .   DOI: 10.1088/0256-307X/40/10/100503
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We take the higher-order nonlinear Schrödinger equation as a mathematical model and employ the bilinear method to analytically study the evolution characteristics of femtosecond solitons in optical fibers under higher-order nonlinear effects and higher-order dispersion effects. The results show that the effects have a significant impact on the amplitude and interaction characteristics of optical solitons. The larger the higher-order nonlinear coefficient, the more intense the interaction between optical solitons, and the more unstable the transmission. At the same time, we discuss the influence of other free parameters on third-order soliton interactions. Effectively regulate the interaction of three optical solitons by controlling relevant parameters. These studies will lay a theoretical foundation for experiments and further practicality of optical soliton communications.
Quantum Squeezing of Matter-Wave Solitons in Bose–Einstein Condensates
Jinzhong Zhu and Guoxiang Huang
Chin. Phys. Lett.    2023, 40 (10): 100504 .   DOI: 10.1088/0256-307X/40/10/100504
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We investigate the quantum squeezing of matter-wave solitons in atomic Bose–Einstein condensates. By calculating quantum fluctuations of the solitons via solving the Bogoliubov–de Gennes equations, we show that significant quantum squeezing can be realized for both bright and dark solitons. We also show that the squeezing efficiency of the solitons can be enhanced and manipulated by atom–atom interaction and soliton blackness. The results reported here are beneficial not only for understanding quantum property of matter-wave solitons, but also for promising applications of Bose-condensed quantum gases.
A Quorum Sensing Active Matter in a Confined Geometry
Yuxin Zhou, Yunyun Li, and Fabio Marchesoni
Chin. Phys. Lett.    2023, 40 (10): 100505 .   DOI: 10.1088/0256-307X/40/10/100505
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Inspired by the problem of biofilm growth, we numerically investigate clustering in a two-dimensional suspension of active (Janus) particles of finite size confined in a circular cavity. Their dynamics is regulated by a non-reciprocal mechanism that causes them to switch from active to passive above a certain threshold of the perceived near-neighbor density (quorum sensing). A variety of cluster phases, i.e., glassy, solid (hexatic) and liquid, are observed, depending on the particle dynamics at the boundary, the quorum sensing range, and the level of noise.
Graviton Momentum: A Natural Source of Dark Energy
Samuel Meng
Chin. Phys. Lett.    2023, 40 (9): 090201 .   DOI: 10.1088/0256-307X/40/9/090201
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The dark energy concept in the standard cosmological model can explain the expansion of the universe. However, the mysteries surrounding dark energy remain, such as its source, its unusual negative pressure, its long-range force, and its unchanged density as the universe expands. We propose a graviton momentum hypothesis, develop a semiclassical model of gravitons, and explain the pervasive dark matter and accelerating universe. The graviton momentum hypothesis is incorporated into the standard model and explains well the mysteries related to dark energy.
Geometric Thermoelectric Pump: Energy Harvesting beyond Seebeck and Pyroelectric Effects
Jie Ren
Chin. Phys. Lett.    2023, 40 (9): 090501 .   DOI: 10.1088/0256-307X/40/9/090501
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Thermal-electric conversion is crucial for smart energy control and harvesting, such as thermal sensing and waste heat recovering. So far, researchers are aware of two main ways of direct thermal-electric conversion, Seebeck and pyroelectric effects, each with different working mechanisms, conditions and limitations. Here, we report the concept of Geometric Thermoelectric Pump (GTEP), as the third way of thermal-electric conversion beyond Seebeck and pyroelectric effects. In contrast to Seebeck effect that requires spatial temperature difference, GTEP converts the time-dependent ambient temperature fluctuation into electricity. Moreover, GTEP does not require polar materials but applies to general conducting systems, and thus is also distinct from pyroelectric effect. We demonstrate that GTEP results from the temperature-fluctuation-induced charge redistribution, which has a deep connection to the topological geometric phase in non-Hermitian dynamics, as a consequence of the fundamental nonequilibrium thermodynamic geometry. The findings advance our understanding of geometric phase induced multiple-physics-coupled pump effect and provide new means of thermal-electric energy harvesting.
Inverse Design of Phononic Crystal with Desired Transmission via a Gradient-Descent Approach
Yuhang Wei and Dahai He
Chin. Phys. Lett.    2023, 40 (9): 090502 .   DOI: 10.1088/0256-307X/40/9/090502
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We propose a general approach based on the gradient descent method to study the inverse problem, making it possible to reversely engineer the microscopic configurations of materials that exhibit desired macroscopic properties. Particularly, we demonstrate its application by identifying the microscopic configurations within any given frequency range to achieve transparent phonon transport through one-dimensional harmonic lattices. Furthermore, we obtain the phonon transmission in terms of normal modes and find that the key to achieving phonon transparency or phonon blocking state lies in the ratio of the mode amplitudes at ends.
Interacting Solitons, Periodic Waves and Breather for Modified Korteweg–de Vries Equation
Vladimir I. Kruglov and Houria Triki
Chin. Phys. Lett.    2023, 40 (9): 090503 .   DOI: 10.1088/0256-307X/40/9/090503
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We theoretically demonstrate a rich and significant new families of exact spatially localized and periodic wave solutions for a modified Korteweg–de Vries equation. The model applies for the description of different nonlinear structures which include breathers, interacting solitons and interacting periodic wave solutions. A joint parameter which can take both positive and negative values of unity appeared in the functional forms of those closed form solutions, thus implying that every solution is determined for each value of this parameter. The results indicate that the existence of newly derived structures depend on whether the type of nonlinearity of the medium should be considered self-focusing or defocusing. The obtained nonlinear waveforms show interesting properties that may find practical applications.
Dark Korteweg–De Vrise System and Its Higher-Dimensional Deformations
Si-Yu Zhu, De-Xing Kong, and Sen-Yue Lou
Chin. Phys. Lett.    2023, 40 (8): 080201 .   DOI: 10.1088/0256-307X/40/8/080201
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The new dimensional deformation approach is proposed to generate higher-dimensional analogues of integrable systems. An arbitrary ($K$+1)-dimensional integrable Korteweg–de Vries (KdV) system, as an example, exhibiting symmetry, is illustrated to arise from a reconstructed deformation procedure, starting with a general symmetry integrable (1+1)-dimensional dark KdV system and its conservation laws. Physically, the dark equation systems may be related to dark matter physics. To describe nonlinear physics, both linear and nonlinear dispersions should be considered. In the original lower-dimensional integrable systems, only liner or nonlinear dispersion is included. The deformation algorithm naturally makes the model also include the linear dispersion and nonlinear dispersion.
Stochastic Gradient Descent and Anomaly of Variance-Flatness Relation in Artificial Neural Networks
Xia Xiong, Yong-Cong Chen, Chunxiao Shi, and Ping Ao
Chin. Phys. Lett.    2023, 40 (8): 080202 .   DOI: 10.1088/0256-307X/40/8/080202
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Stochastic gradient descent (SGD), a widely used algorithm in deep-learning neural networks, has attracted continuing research interests for the theoretical principles behind its success. A recent work reported an anomaly (inverse) relation between the variance of neural weights and the landscape flatness of the loss function driven under SGD [Feng Y and Tu Y Proc. Natl. Acad. Sci. USA 118 e2015617118 (2021)}]. To investigate this seeming violation of statistical physics principle, the properties of SGD near fixed points are analyzed with a dynamic decomposition method. Our approach recovers the true “energy” function under which the universal Boltzmann distribution holds. It differs from the cost function in general and resolves the paradox raised by the anomaly. The study bridges the gap between the classical statistical mechanics and the emerging discipline of artificial intelligence, with potential for better algorithms to the latter.
Stochastic Resonance in a Single-Ion Nonlinear Mechanical Oscillator
Tai-Hao Cui, Ji Li, Quan Yuan, Ya-Qi Wei, Shuang-Qing Dai, Pei-Dong Li, Fei Zhou, Jian-Qi Zhang, Liang Chen, and Mang Feng
Chin. Phys. Lett.    2023, 40 (8): 080501 .   DOI: 10.1088/0256-307X/40/8/080501
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Stochastic resonance is a counterintuitive phenomenon amplifying the weak periodic signal by application of external noise. We demonstrate the enhancement of a weak periodic signal by stochastic resonance in a trapped-ion oscillator when the oscillator is excited to the nonlinear regime and subject to an appropriate noise. Under the full control of the radio-frequency drive voltage, this amplification originates from the nonlinearity due to asymmetry of the trapping potential, which can be described by a forced Duffing oscillator model. Our scheme and results provide an interesting possibility to make use of controllable nonlinearity in the trapped ion, and pave the way toward a practical atomic sensor for sensitively detecting weak periodic signals from real noisy environment.
Soliton Interactions with Different Dispersion Curve Functions in Heterogeneous Systems
Xinyi Zhang and Ye Wu
Chin. Phys. Lett.    2023, 40 (8): 080502 .   DOI: 10.1088/0256-307X/40/8/080502
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In practical optical communication systems, there are some factors that can affect transmission quality of optical solitons. The constant coefficient nonlinear Schrödinger (NLS) equation has been unable to meet the actual research needs. We need to use the variable coefficient NLS equation to simulate an actual system, so as to explore its potential application value. Based on the variable coefficient NLS equation, six dispersion decreasing fibers (DDFs) with different dispersion curve functions are used as transmission media to study generation and interaction of two solitons in an optical communication system. The two soliton interaction phenomena, such as the bound state solitons, are theoretically obtained. Moreover, the output characteristics of bound state solitons in different DDFs are discussed, which enriches the transmission phenomenon of two solitons in the optical communication system. This study has great application value in fields such as optical information processing devices, condensed matter physics, and plasma, and provides an indispensable theoretical basis for development of new optical devices.
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