arXiv subjects

T. Wang

Publications and source records attributed to T. Wang.

At least 19 recordsLinked to original sources

arXiv2026

Excitation caging in a vertex-frustrated quasiperiodic Einstein artificial spin ice

Naturally occurring bulk quasicrystals are rare, and magnetic instances are rarer still, with chemical constraints typically permitting the synthesis of approximants rather than true quasicrystalline magnets. Here, we present an artificial spin ice based on a recently discovered Einstein lattice, the Hat tiling, which is built from the first known shape - the hat - that tiles the plane only aperiodically. The Einstein artificial spin ice has long-range structural order with no translational symmetry, and low-connectivity vertices with well-defined local ground states and excitations. Together, these properties provide a model two-dimensional quasicrystalline magnet, with magnetic correlations that we probe with magnetic force microscopy and parallel-tempered Monte Carlo simulations. We identify a two-stage partial ordering process, driven by the competition between two possible positions for magnetic excitations. This competition is resolved in the ground-state manifold, where exactly one magnetic excitation is caged on each antihat, yet the manifold remains macroscopically degenerate. This yields an unusual type of medium-range order, where the underlying quasiperiodic long-range order is randomly modulated by a strictly constrained disorder. Our findings establish the Einstein artificial spin ice as a blueprint for understanding quasicrystalline magnetism, demonstrating how quasiperiodic monotile geometries can be exploited to engineer unconventional magnetic phases with no direct equivalent in periodic systems.

cond-mat.mes-hall↗

arXiv2026

Relativistic effects of PSR~J1856--0039 double neutron star system in a 2.36-hour compact orbit

Compact double neutron star (DNS) systems are unique laboratories for testing gravitational theories and studying DNS mergers. Here we report the properties of a new DNS system, PSR J1856--0039, discovered in the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The pulsar is mildly recycled with a period of 23.4~ms in a compact eccentric orbit ($e=0.106$) with an orbital period of 2.36 hours. By following up FAST observations, we measured the relativistic effects, including the orbital period derivative $\dot{P}_{\rm orb}=-1.284\pm0.019\times10^{-12}$ s s$^{-1}$, periastron advance $\dot\omega=17.5859\pm0.0007$ deg yr$^{-1}$, and Einstein delay $\gamma=0.445\pm0.011$ ms. This DNS system has a low orbital inclination of $i=133^\circ.2\pm1^\circ.1$ and the lowest total mass of any known DNS, $M_{\rm tot}=2.48841\pm0.00015 M\odot$, with a determined pulsar mass of $1.304\pm0.022 M_\odot$ and a companion mass of $1.185\pm0.022 M_\odot$, one of the lowest neutron-star masses. The observed orbital decay due to gravitational-wave emission $\dot{P}^{\rm GW}_{\rm orb,obs}$ and the orbital decay predicted by general relativity $\dot{P}^{\rm GW}_{\rm orb,pred}$ are consistent at a level of $\dot{P}^{\rm GW}_{\rm orb,obs}/\dot{P}^{\rm GW}_{\rm orb,pred}=$1.009(14) (68% confidence). This DNS will merge after 82 Myr and may form a stable neutron star or collapse into a black hole after spin-down. Long-term monitoring could potentially probe the Lense-Thirring precession.

astro-ph.HE↗

arXiv2026

FAST Pulsar Database III. Snapshots of nulling, mode-changing and subpulse modulation of 374 pulsars

Based on sensitive L-band (1.0 to 1.5 GHz) observations of pulsars using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we analyzed single-pulse sequences from FAST-detected pulsars and identified nulling, mode changing, or subpulse modulation phenomena in 374 sources. Among these, nulling has been detected in 160 pulsars, with 127 cases reported for the first time. Emission mode changes have been observed in 52 pulsars, including 51 first-time detections. Subpulse modulation has been identified in 272 pulsars, 180 of which are newly revealed, with the majority displaying subpulse drifting behavior. Subpulse drifting in some pulsars exhibits distinct modes with varying drift properties, leading to mode changes and divergent mean profiles. Statistics on pulsar parameters show that pulsars exhibiting nulling and/or subpulse modulation tend to be older, with longer periods and lower spin-down energy-loss rates. The modulation period P3 is predominantly correlated with pulsar rotation periods, magnetic field strengths, and spin-down energy loss.

astro-ph.HE↗

arXiv2026

High-Rate Free-Space Continuous-Variable QKD with Self-Referenced Passive State Preparation

Continuous-variable quantum key distribution (CVQKD) using passive state preparation (PSP) offers low-cost, high-rate secure communication. However, the existing PSP-CVQKD scheme with a transmitted local oscillator has high photon leakage noise and poor stability, making it unsuitable for high-loss transmission. In this work, for the first time, we propose and implement a local local oscillator (LLO) CVQKD system using a self-referenced (SR) PSP scheme, and give a theoretical proof of the equivalence of the PSP and GMCS protocol using temporal-mode theory. By employing the novel self-referenced pilot scheme to achieve high-precision time-varying frequency and phase compensation algorithms, we significantly improve the system' s signal-to-noise ratio and stability. The system achieves a record-high asymptotic secret key rate of 10.34 Mbps over a free-space channel with up to 23.5 dB loss, while maintaining low excess noise and robust performance under turbulent conditions. This work establishes the feasibility of SR-LLO CVQKD, providing a practical pathway toward secure, high-rate quantum communication in realistic environments.

quant-ph↗

arXiv2026

High-key-rate Fully-Passive Quantum Access Network with Thermal Source

To accommodate classical communication systems with progressively increasing transmission rates, quantum access networks (QAN) have undergone systematic and protocol-level optimizations in recent years, where quantum passive optical network (QPON) architectures are gaining significant attention due to their simple structure. It is challenging for the previous QAN based on active protocols or Stokes operator coding protocols to achieve high-speed linear modulation with high extinction ratio and stability under practical conditions. In this work, we propose and experimentally demonstrate a downstream fully passive quantum access network protocol using passive state preparation (PSP) with free-space and single-mode fiber hybrid channels, and the final key generation rate is up to a record-breaking 19.48 Mbps per quantum network unit. The proposed PSP-QPON scheme extends the scope of PSP-CVQKD from point-to-point to point-to-multi-point networks, which enables high-key-rate, high-stability, and low-resource-consumption implementation. Moreover, the network channel in this experiment is fully compatible with access networks in classical optical communications, which allows integration with existing optical infrastructure without the need for additional modifications, providing a promising solution for local area network quantum access network at home or a mobile terminal.

quant-ph↗

arXiv2026

Simultaneous Multi-band Optical Follow-up Observations of a Gamma-Ray Flare in BL Lacertae

On $2024$ October $5$, BL Lacertae ($2200+420$) experienced one of its brightest gamma-ray flares. We conducted simultaneous follow-up observations in the $u$, $v$, $g$, $r$, $i$, and $z$ bands from $2024$ October $17$ to November $21$ using the Mephisto telescope and its two $50$ cm twin auxiliary photometric telescopes of Yunnan University. Intraday variability (IDV) was detected in the $g$, $r$, $i$, and $z$ bands. The IDV duty cycle increased with observing frequency across these bands. The shortest variability time-scale, derived from auto-correlation analysis, constrains the upper limit of the black hole mass to be $M_{\bullet} \lesssim 10^{8.29} M_{\odot}$ assuming a Kerr black hole, and $M_{\bullet} \lesssim 10^{8.77} M_{\odot}$ assuming a Schwarzschild black hole. The emission region responsible for the observed variability has a size of $R \le 3.51 \times 10^{14}$ cm and is located at a distance of $R_H \le 2.83 \times 10^{15}$ cm from the central supermassive black hole. This distance is approximately three orders of magnitude smaller than the typical radius of the broad-line region, indicating that the emission region lies well within it. A general bluer-when-brighter (BWB) trend was detected on intraday time-scales, suggesting that shock-accelerated relativistic electrons enhance the high-energy particle population, leading to spectral hardening. A potential quasi-periodic oscillation (QPO) with a period of $\sim 100.77$ minutes was detected with $>99.99$ per cent confidence, consistent with predictions from the magnetic reconnection model. These observed optical intraday variabilities and colour variations of BL Lacertae can be well explained by the turbulent jet model.

astro-ph.HE↗

arXiv2026

The FAST Galactic Plane Pulsar Snapshot Survey. IX. Timing Three Binary Pulsars with Wide Orbits and Low Orbital Eccentricities

Current pulsar timing models face challenges when applied to binary pulsars with wide orbits and low orbital eccentricities. The conventional \texttt{DD} model accurately characterizes the orbits of such systems, but it suffers from strong correlations between the time of periastron passage ($T_0$) and the longitude of periastron ($\omega$). The ELL1 model avoids these parameter correlations, yet fails due to the limitations of its first-order low-eccentricity approximation. Recent enhancements to the ELL1 model (dubbed ELL1+ model) have incorporated higher-order terms but retain the low-eccentricity approximation. In this study, we propose a further improved model, ELL1R, which eliminates reliance on the low-eccentricity approximation through rigorous calculation of the R\"{o}mer delay. This modification can avoid strong parameter correlations in the DD model, and it can be used in systems with mild eccentricity $0.01\lesssim e\lesssim0.1$ where the ELL1+ model can not. Using the ELL1R model, we present the first phase-coherent timing solutions for three binary pulsars: PSR~J1851--0108 (orbital period: 228 days), PSR~J1910+0423 (886 days), and PSR~J1923+2022 (777 days). Validation against the DD and ELL1+ models confirms that ELL1R yields consistent timing results while integrating the advantages of the two models. Our analysis further indicates that all three pulsars are mildly recycled. The companions of PSRs J1910+0423 and J1923+2022 are likely white dwarfs, whereas the nature of PSR J1851--0108's companion remains unknown.

astro-ph.HE↗

arXiv2026

Mass measurements of the double neutron star system PSR J0641+0448

Pulsar timing of double neutron star (DNS) systems is one of the best methodologies to study the neutron star masses distribution. Here we report the discovery of a double neutron star system PSR J0641+0448 in the Five-hundred-meter Aperture Spherical radio Telescope (FAST) Galactic Plane Pulsar Snapshot (GPPS) survey. This pulsar has a 25.7 ms spin period and moves in a 3.73-days eccentric orbit with an eccentricity of 0.145. Using FAST observations, we obtained its phase-connected timing solution with periastron advance and Shapiro delay detected. Using $\chi^2$ analysis based on DDGR model, we constrain the pulsar mass to $1.319^{+0.021}_{-0.035}~M_\odot$, and the companion mass to $1.269^{+0.022}_{-0.016}~M_\odot$ with a 68.3\% confidence level. The low companion mass and mild orbital eccentricity is consistent with the correlation between neutron masses and orbital eccentricities.

astro-ph.HE↗

arXiv2026

Polarization-Multiplexed Chaotic LiDAR Based on a VCSEL with Delayed Orthogonal Feedback

Light detection and ranging (LiDAR) systems are pivotal for precise distance and velocity measurement, yet widespread deployment requires solutions that balance their performance, robustness, and simplicity. Here, we propose a novel chaotic LiDAR system based on a semiconductor vertical-cavity surface-emitting laser (VCSEL) with delayed orthogonal polarization feedback. By exploiting the intrinsic competition between the transverse electric (TE) and transverse magnetic (TM) modes, the system generates a polarization-multiplexed dynamics: a chaotic TM mode serves as the reference, while a feedback-modulated TE mode probes the target. This all-in-one source eliminates the need for external optical modulators or complex coherent detection. The system's dynamics is finely tunable via a half-wave ($\lambda$/2) plate in the feedback loop and the laser injection current, enabling real-time optimization of the cross-correlation signal-to-noise ratio. Experimental results demonstrate precise linear ranging with a resolution of approximately 1.2 cm. Furthermore, the system exhibits strong inherent resistance to external optical interference, maintaining accurate ranging even in the presence of a secondary laser source. This compact, tunable, and interference-resilient platform offers a promising pathway toward low-cost, high-performance LiDAR for applications in autonomous navigation, robotics, and industrial metrology.

physics.optics↗

arXiv2026

Deterministic Control of Extreme Events in a semiconductor VCSEL via Polarization-Engineered Optical Feedback

Extreme events, or rogue waves, are high-amplitude, rare occurrences that emerge across diverse physical systems and often defy conventional statistical predictions. While optical systems provide a controlled setting for studying these phenomena, achieving deterministic control over their generation remains challenging. Here, we demonstrate a novel approach to induce and precisely modulate extreme events in a semiconductor VCSEL using polarization-controlled optical feedback. By integrating a $\lambda$/2-waveplate into a polarization-selective external cavity, we regulate the nonlinear interaction between TE and TM modes. This setup triggers high-intensity, heavy-tailed fluctuations in the TM mode, exhibiting clear signatures of extreme events. We show that these events arise from deterministic energy exchange between modes, as evidenced by strong bipolar correlations and long-range temporal memory. The waveplate angle serves as an effective external parameter, enabling non-monotonic tuning of the event rate, intensity, and temporal clustering. Our study establish a platform for exploring extreme events in dissipative systems, with implications for nonlinear photonics and optical technologies.

physics.optics↗

arXiv2026

Inverse Design of Tunable Infrared Metasurface Absorbers via a Conditional Wasserstein Generative Adversarial Network

Narrowband perfect absorbers are interesting for spectrum sensing, molecular detection, and infrared imaging. However, their design remains constrained by intuitive, iterative methods that lack flexibility, while also facing challenges in multi-objective optimization. Here, we introduce a deep learning-enabled inverse-design framework that overcomes these limitations through a conditional Wasserstein Generative Adversarial Network (WGAN). The main contribution of this work is a dual-channel image encoding scheme that jointly represents the geometry and thickness of a Si$_3$N$_4$ meta-layer, facilitating the network to learn the distribution of viable structures for a target optical response. This approach naturally solves the inherent ``one-to-many'' design issue, giving a diverse portfolio of functional candidates from a single input spectrum. The designed absorbers achieve exceptional spectral fidelity, with resonance peak errors below 5 nm, a mean squared error (MSE) on the order of $10^{-3}$, and the capacity to produce over 10 distinct, high-performance designs per target. Furthermore, we demonstrate the model's robustness under oblique illumination, showing that it can be efficiently fine-tuned to maintain spectral accuracy across incidence angles from $10^\circ$ to $40^\circ$ by transfer learning, thus extending its practical utility to non-normal operating conditions. Full-wave simulations confirm that the generated geometries support a hybrid plasmonic-dielectric resonance, leading to near-perfect absorption and strong near-field enhancement. Our study provides a robust, physics-aware design paradigm that moves beyond conventional parametric optimization. The introduced framework establishes a versatile platform for the on-demand inverse design of advanced photonic devices for sensing, spectroscopy, and optical signal processing.

physics.optics↗

arXiv2025

UHDRes: Ultra-High-Definition Image Restoration via Dual-Domain Decoupled Spectral Modulation

Ultra-high-definition (UHD) images often suffer from severe degradations such as blur, haze, rain, or low-light conditions, which pose significant challenges for image restoration due to their high resolution and computational demands. In this paper, we propose UHDRes, a novel lightweight dual-domain decoupled spectral modulation framework for UHD image restoration. It explicitly models the amplitude spectrum via lightweight spectrum-domain modulation, while restoring phase implicitly through spatial-domain refinement. We introduce the spatio-spectral fusion mechanism, which first employs a multi-scale context aggregator to extract local and global spatial features, and then performs spectral modulation in a decoupled manner. It explicitly enhances amplitude features in the frequency domain while implicitly restoring phase information through spatial refinement. Additionally, a shared gated feed-forward network is designed to efficiently promote feature interaction through shared-parameter convolutions and adaptive gating mechanisms. Extensive experimental comparisons on five public UHD benchmarks demonstrate that our UHDRes achieves the state-of-the-art restoration performance with only 400K parameters, while significantly reducing inference latency and memory usage. The codes and models are available at https://github.com/Zhao0100/UHDRes.

eess.IV↗

arXiv2025

FAST Pulsar Database: II. Scattering profiles of 149 Pulsars

The turbulent ionized interstellar medium diffracts radio waves and makes them propagate in multiple paths. The pulse-broadening observed at low frequencies results from the scattering effect of interstellar clouds of ionized gas. During the Galactic Plane Pulsar Snapshot (GPPS) survey and other projects by using the Five-hundred-meter Aperture Spherical radio Telescope (FAST), we detect the pulse-broadening for 149 pulsars in the radio frequency band between 1.0 and 1.5 GHz, including 68 newly discovered pulsars in the GPPS survey and 81 previously known pulsars. We find that a more accurate dispersion measure can be obtained from aligning the front edge of the scattered subband pulses at the 1/4 or 1/2 peak level for most pulsars with one dominant component in the intrinsic profile, and the best DM values from aligning the intrinsic profile components from the model-fitting. From the pulse profiles at a few subbands we derive the pulse-broadening timescale and the scattering spectral index. These scattering parameters are measured for the first time for 113 pulsars. For 36 pulsars with previously detected scattering features, our measurements of the pulse-broadening timescale are consistent with results in the literature. We find that pulsars behind spiral arms show a stronger scattering effect due to greater density fluctuations in the arm regions. With a properly derived dispersion measure and careful calibration, we also present polarization profiles for 82 pulsars in three subbands of FAST observations.

astro-ph.HE↗

arXiv2025

A pulsar-helium star compact binary system formed by common envelope evolution

A stellar common envelope occurs in a binary system when the atmosphere of an evolving star expands to encompass an orbiting companion object. Such systems are predicted to evolve rapidly, ejecting the stellar envelope and leaving the companion in a tighter orbit around a stripped star. We used radio timing to identify a pulsar, PSR J1928+1815, with a spin period of 10.55 ms in a compact binary system with an orbital period of 3.60 hours. The companion star has 1.0 to 1.6 solar masses, eclipses the pulsar for about 17% of the orbit, and is undetected at other wavelengths, so it is most likely a stripped helium star. We interpret this system as having recently undergone a common envelope phase, producing a compact binary.

astro-ph.HE↗

arXiv2025

Mode locking via delayed orthogonal-polarization reinjection in semiconductor VCSELs

We demonstrate harmonic mode-locking in a semiconductor VCSEL using polarization-controlled delayed feedback. By integrating a rotatable $\lambda$/2-plate within an external cavity, we achieve precise control over pulse multiplicity and repetition rates in TE and TM modes. For the TE mode, increasing the $\lambda$/2-plate angle ($\theta$) transitions the system from disordered quasi-periodic states to stable fundamental (single-pulse) and harmonic dual-pulse mode-locking. Polarization-resolved measurements and cross-correlation analyses reveal coherent pulse alignment at half the cavity roundtrip time, enabled by polarization-mediated nonlinear dynamics. This work establishes cross-polarization feedback as a fundamental mechanism for ultrafast pulse engineering, advancing the understanding of polarization-mediated nonlinear dynamics in laser physics.

physics.optics↗

arXiv2025

Enhanced shot noise in graphene quantum point contacts with electrostatic reconstruction

Shot noise measurements in quantum point contacts are a powerful tool to investigate charge transport in the integer and fractional quantum Hall regime, in particular to unveil the charge, quantum statistics and tunneling dynamics of edge excitations. In this letter, we describe shot noise measurements in a graphene quantum point contact in the quantum Hall regime. At large magnetic field, the competition between confinement and electronic interactions gives rise to a quantum dot located at the saddle point of the quantum point contact. We show that the presence of this quantum dot leads to a $50-100~\%$ increase in the shot noise, which we attribute to correlated charge tunneling. Our results highlight the role played by the electrostatic environment in those graphene devices.

cond-mat.mes-hall↗

arXiv2025

Design and Commissioning of Readout Electronics for a $K_L^0$ and $\mu$ Detector at the Belle II Experiment

The K-long and muon detector (KLM) constitutes the outer-most volume of the Belle II spectrometer at the interaction region of the SuperKEKB collider in Tsukuba, Japan. The KLM detector was partially upgraded since the Belle experiment by replacing many of its resistive-plate chambers with scintillators containing wavelength-shifting fibers and instrumenting it with silicon photomultipliers. We describe the readout electronics, firmware, and software created to control and acquire data from the scintillators and resistive-plate chambers.

hep-ex↗

arXiv2024

DeepSeek-V3 Technical Report

We present DeepSeek-V3, a strong Mixture-of-Experts (MoE) language model with 671B total parameters with 37B activated for each token. To achieve efficient inference and cost-effective training, DeepSeek-V3 adopts Multi-head Latent Attention (MLA) and DeepSeekMoE architectures, which were thoroughly validated in DeepSeek-V2. Furthermore, DeepSeek-V3 pioneers an auxiliary-loss-free strategy for load balancing and sets a multi-token prediction training objective for stronger performance. We pre-train DeepSeek-V3 on 14.8 trillion diverse and high-quality tokens, followed by Supervised Fine-Tuning and Reinforcement Learning stages to fully harness its capabilities. Comprehensive evaluations reveal that DeepSeek-V3 outperforms other open-source models and achieves performance comparable to leading closed-source models. Despite its excellent performance, DeepSeek-V3 requires only 2.788M H800 GPU hours for its full training. In addition, its training process is remarkably stable. Throughout the entire training process, we did not experience any irrecoverable loss spikes or perform any rollbacks. The model checkpoints are available at https://github.com/deepseek-ai/DeepSeek-V3.

cs.CL↗