arXiv subjects

L. Huang

Publications and source records attributed to L. Huang.

At least 19 recordsLinked to original sources

arXiv2026

High-Fidelity Entangled States in a Connectivity-Four Fluxonium Quantum Processor

A central challenge in fluxonium-based quantum processors is the extension of the qubit connectivity to two-dimensional lattices compatible with quantum code-error correction. Here, we present a fluxonium quantum processor that employs lumped-element resonator couplers which realizes, for the first time, a connectivity-four unit cell with suppressed parasitic interactions. We achieve parallel single-qubit gate fidelities exceeding 99.9 % in simultaneous randomized benchmarking experiments, while maintaining residual static ZZ interactions below 1 kHz across all coupled qubit pairs. We implement resonator-induced phase (RIP) gates and benchmark two-qubit gate fidelities exceeding 99 % using interleaved randomized benchmarking. To cancel spectator errors observed in two-qubit operations, we implement a refocused RIP gate, recovering coherent control in the presence of multi-qubit connectivity. Furthermore, we prepare Greenberger-Horne-Zeilinger states of up to five qubits with a tomographic fidelity of 90 %, verifying multi-qubit entanglement within the unit cell. These results establish the fluxonium-resonator-fluxonium architecture as a viable approach to realizing densely connected fluxonium processors and provide a scalable path toward quantum error-correction-compatible processor architectures.

quant-ph↗

arXiv2026

Multibranched parametric resonance and swallowtail catastrophe in electromechanical oscillators with nonlinear friction

Parametric resonance underpins the operation of a wide range of physical systems, from nanomechanical resonators to quantum-information systems and Ising machines. As an archetypal class of driven-dissipative systems, parametric oscillators are generally expected to exhibit a single pair of stable period-two states with opposite phases. This bistable behavior enables both the simulation of spin Hamiltonians and the preparation of superconducting cat states. Whether multiple pairs of such states can coexist in a single oscillator, however, remains an open question. Here, we show experimentally and theoretically that conventional controlled nonlinear friction can induce the coexistence of two distinct pairs of period-two states in a micromechanical oscillator. The friction is implemented via a canonical approach, utilizing a drive-induced resonant coupling that transfers two vibrational quanta from the oscillatory mode to a faster decaying mode. We demonstrate that the onset of multistability is governed by a swallowtail catastrophe and quantitatively map the associated bifurcation structure. Our results broaden the understanding of parametric resonance and establish micro- and nano-mechanical oscillators as a versatile platform for studying catastrophe theory and multistable nonequilibrium dynamics.

physics.class-ph↗

arXiv2026

Experimental straintronics in nanotube quantum dots

Single-wall carbon nanotubes (SWCNTs) are narrow ribbons of graphene with atomically precise edges and a single quantum transport channel, at experimentally-relevant dopings. This makes them ideal systems to harness quantum transport straintronics (QTS), i.e. using mechanical strain to control accurately quantum transport. We present QTS data from three single-wall carbon nanotube quantum dot (SWCNT-QD) transistors over a broad range of in-situ tunable and reversible uniaxial strain ($\Delta\varepsilon_\text{mech}\approx$ 0 to 3 %). We first present the nanofabrication of the suspended SWCNT transistors whose channel lengths are $\approx$ 30 nm. The channels are strained by moving gold clamps holding firmly the nanotubes. We present detailed charge transport data, $dI/dV_{\text{B}} - V_{\text{B}} - V_{\text{G}}$ and $dI/dV_{\text{B}} - V_{\text{B}} - \Delta\varepsilon_\text{mech}$, showing a large mechanical-gating effect of the SWCNT-QDs. The precise reversibility of the data, and their agreement with QTS theory, confirms that the tubes are strained elastically. We demonstrate that the mechanical control of the QD doping is not due to capacitive-gating effects, but to quantitatively predictable bandstructure changes including a strain-tunable bandgap. This precise mechanical control of the doping and bandgap of SWCNT-QDs could find applications in qubits, condensed matter physics, and homojunction molecular transistors.

cond-mat.mes-hall↗

arXiv2026

XRF 241001A/SN 2024aiiq: A faint soft X-ray transient detected by SVOM with a broad-line type Ic supernova revealed by JWST

X-ray flashes (XRFs) are a type of gamma-ray burst (GRB) with prompt emission predominantly below 30 keV and have been poorly detected by previous missions. The advent of the SVOM mission, with its wide-field instrument ECLAIRs, provides a new way to detect soft X-ray transients. We present photometric and spectroscopic observations of XRF 241001A detected by SVOM, a soft, subluminous, and low-energetic burst located in a poorly populated region of the Amati relation. We investigated the origin of its faint, soft high-energy emission to assess its connection to the long GRB population. We analyzed the SVOM/ECLAIRs prompt emission and modeled its afterglow emission from X-ray to-radio. We present JWST/NIRSpec and SVOM/VT observations of the associated supernova (SN 2024aiiq), and we compared its properties with previously detected GRB/SNe. The event XRF 241001A is located at z = 0.573 and has a prompt emission dominated by photons below 20 keV with a duration of T90 = 3.14 seconds. Its spectrum is consistent with both thermal and nonthermal models, each implying a low Epeak < 10 keV and Eiso ~ 8x10^49 erg. The X-ray-to-radio afterglow modeling favors an origin from a relativistic jet viewed on-axis. In the optical, XRF 241001A exhibits an early blue emission, similar to that detected in some eFXTs and inconsistent with synchrotron emission. The JWST/NIRSpec observations firmly established its collapsar origin by revealing a SN Type Ic with broad lines, comparable to SN 1998bw and SN 2025kg-like events. The event XRF 241001A is a soft low-luminosity collapsar event produced by a weak relativistic jet observed on-axis, supporting the view that part of the XRF population forms the low-energy soft tail of the long GRB population. Its observation demonstrates the potential of SVOM/ECLAIRs to probe the soft regime of the high-energy transient population that remains largely unexplored.

astro-ph.HE↗

arXiv2026

Multi-wavelength Study of A Superflare on RS CVn-type Star HD22468 Triggered at Hard X-ray by SVOM

Detection of stellar flares at hard X-ray is still rare at the current stage. A transient was recently detected by the hard X-ray camera, ECLAIRs onboard the SVOM mission at 11:39:01.2UT on 2025, January 09. Simultaneous monitor in the optical band on the ground by SVOM/GWAC and follow-up spectroscopy enable us to confirm that the transient is caused by a superflare on HD~22468, a RS CVn-type star. The bolometric energy released in the flare is estimated to be $\sim7.2\times10^{37}-1.7\times10^{38}\ \mathrm{erg}$. The hard X-ray spectra of the event at the peak can be reproduced by the ``apec'' model of a hot plasma with a temperature of $106^{+27}_{-22}$~MK. In the optical range, the H$\alpha$ emission-line profile obtained at $\sim1.7$ hrs after the trigger shows a bulk blueshift of $-96\pm20\ \mathrm{km\ s^{-1}}$, which can be explained by either a chromospheric evaporation or a prominence eruption. The ejected mass is estimated to be $3.9\times10^{20}$ g for the evaporating plasma, and to be $3.2\times10^{21}\ \mathrm{g}<M_{\mathrm{p}}<8.8\times10^{21}\ \mathrm{g}$ for the erupted prominence.

astro-ph.SR↗

arXiv2026

SVOM discovery of a strong X-ray outburst of the blazar 1ES~1959+650 and multi-wavelength follow-up with the Neil Gehrels Swift observatory

On December 6, 2024, 1ES 1959+650, one of the X-ray brightest blazars known, underwent a high-amplitude X-ray outburst detected by SVOM, the first such discovery with this mission. The source was subsequently monitored with SVOM and Swift from December 2024 to March 2025. We report the detection and multi-wavelength follow-up of this event, and describe the temporal and spectral evolution observed during the campaign. Data from SVOM/MXT, SVOM/ECLAIRs, and Swift/XRT were analyzed with log-parabola models to track flux and spectral variability. The source was detected in a bright state over the 0.3-50 keV range. During the three months of monitoring, the X-ray flux varied significantly, showing episodes of spectral hardening at high flux levels. The spectral curvature evolved more irregularly and did not show a clear trend with flux. A shift of the Spectral Energy Distribution (SED) synchrotron peak to higher energies is seen when the flux increases. This constitutes the first blazar outburst discovered in X-rays by SVOM. The coordinated follow-up with Swift provided continuous coverage of the flare and highlights the strong complementarity of the two missions for time-domain studies of blazars. The flare shows no clear signatures of either Fermi I or Fermi II acceleration, suggesting a mixed Fermi I/II scenario.

astro-ph.HE↗

arXiv2025

Hybrid Superscattering Driven by Toroidal Dipole

The dynamic toroidal dipole is a unique radiation source beyond standard multipoles. Since its first demonstration 15 years ago, it has attracted growing theoretical and experimental interest. Research mainly aims to enhance its weak electromagnetic coupling to free space. Here we report on a surprising finding that the toroidal dipole can, in fact, be engaged in the enhancement of electromagnetic scattering per se driving the so-called superscattering the regime of anomalously strong light scattering where the total cross-section of the effect exceeds the fundamental single-channel limit. We introduce a new paradigm of hybrid superscattering enabled by the toroidal dipole, which we implement with a dielectric scatterer of a simple geometry, and demonstrate for the first time that two complementary mechanisms of superscattering the Friedrich-Wintgen mechanism and resonance overlap can act synergistically to yield the substantially enhanced effect. Using coupled-dipole theory, full-wave numerical modeling and coupled-mode theory, we identify and quantify the dominant multipolar contributions and show that the normalized scattering cross-section exceeds the dipole limit due to a toroidal dipole-magnetic quadrupole interplay. These findings are supported by experimental measurements in the GHz frequency range using a dimer of ceramic cubes, which confirm both the spectral and spatial features of toroidal superscattering. Our results open a new powerful route to engineering strong light-matter interaction via peculiar toroidal modes (never observed before) with potential applications in toroidal superscattering metamaterials and metasurfaces, photonic devices, and sensors.

physics.optics↗

arXiv2025

Imaging the Photochemistry of Cyclobutanone using Ultrafast Electron Diffraction: Experimental Results

We investigated the ultrafast structural dynamics of cyclobutanone following photoexcitation at $\lambda=200$ nm using gas-phase megaelectronvolt ultrafast electron diffraction. Our investigation complements the simulation studies of the same process within this special issue. It provides information about both electronic state population and structural dynamics through well-separable inelastic and elastic electron scattering signatures. We observe the depopulation of the photoexcited S$_2$ state of cyclobutanone with n3s Rydberg character through its inelastic electron scattering signature with a time constant of $(0.29 \pm 0.2)$ ps towards the S$_1$ state. The S$_1$ state population undergoes ring-opening via a Norrish Type-I reaction, likely while passing through a conical intersection with S$_0$. The corresponding structural changes can be tracked by elastic electron scattering signatures. These changes appear with a delay of $(0.14 \pm 0.05)$ ps with respect the initial photoexcitation, which is less than the S$_2$ depopulation time constant. This behavior provides evidence for the ballistic nature of the ring-opening once the S$_1$ state is reached. The resulting biradical species react further within $(1.2 \pm 0.2)$ ps via two rival fragmentation channels yielding ketene and ethylene, or propene and carbon monoxide. Our study showcases both the value of gas-phase ultrafast diffraction studies as an experimental benchmark for nonadiabatic dynamics simulation methods and the limits in the interpretation of such experimental data without comparison to such simulations.

physics.chem-ph↗

arXiv2025

Enhancing Fault Diagnosis in GWAC: A Monitoring System for Telescope Arrays

The Ground-based Wide-Angle Cameras array (GWAC) necessitates the integration of over 100 hardware devices, more than 100 servers, and upwards of 2500 software modules, all synchronized within a 3-second imaging cycle. However, the complexity of real-time and high concurrency processing of big data have historically resulted in a substantial failure rate, with estimated observation efficiency of less than 50% in 2023. To address these challenges, we developed a monitoring system aimed at enhancing fault diagnosis efficiency. The system features two innovative monitoring views: state evolution monitoring and transient lifecycle monitoring. These, combined with instantaneous state monitoring and key parameter monitoring views, create a comprehensive and holistic monitoring strategy. This paper details the system's architecture, data collection methods, and the design philosophy of monitoring views. After a year of practical fault diagnostics, the system has demonstrated the ability to identify and localize faults within minutes, achieving fault localization speeds nearly ten times faster than traditional methods. Additionally, the system's design exhibits high generalizability, making them applicable to other telescope array systems.

astro-ph.IM↗

arXiv2024

A distance measurement of galaxies from JWST using star formation rate-stellar mass relation

We use the star formation rate-stellar mass relation ($SFR - {M_ * }$) of galaxies to measure their luminosity distances as well as estimate cosmological parameters. We compile a sample of 341 high-redshift galaxies at $5 < z < 14$ and an additional 51 galaxies at $1.8 < z < 3.5$ from the JWST observations, which can be used to investigate the correlation between the star formation rate and stellar mass, and determine their cosmological distance. The relation $SFR \propto {\kern 1pt} {({M_ * }/{M_ \odot })^\gamma }$ can be applied to check the nonlinear correlation between the star formation rate and stellar mass ${M_ * }$ of galaxies and give their distance. Additionally, it also can be used to test if the $SFR - {M_ * }$ relation depends on redshift, and the data suggest that the $SFR $ is positively correlated with stellar mass, the $SFR - {M_ * }$ relation of the high-redshift galaxies has a redshift dependence. Finally, we combine the galaxy sample with Type Ia supernova (SNIa) data from the Pantheon compilation to test the property of dark energy, specifically addressing whether its density deviates from the constant, and give the statistical analysis results.

astro-ph.CO↗

arXiv2024

Quantum Transport Straintronics and Mechanical Aharonov-Bohm Effect in Quasi-metallic SWCNTs

Single-wall carbon nanotubes (SWCNTs) are effectively narrow ribbons of 2D materials with atomically precise edges. They are ideal systems to harness quantum transport straintronics (QTS), i.e. using mechanical strain to control quantum transport. Their large subband energy spacing ($\sim$ 0.8 eV) leads to transistors with a single quantum transport channel. We adapt an applied model to study QTS in uniaxially-strained quasi-metallic-SWCNT transistors. The device parameters are based on an existing experimental platform, with channel lengths of $L=$ 50 nm, diameters $d\approx$ 1.5 nm, and strains up to $\varepsilon_{\text{tot}}\approx$ 7 $\%$. We demonstrate that the charge carrier's propagation angle $\Theta$ is fully tunable with $\varepsilon_{\text{tot}}$. When $\Theta$ reaches 90$^o$, the conductance $G$ is completely suppressed. A strain-generated band gap can be tuned up to $\approx$ 400 meV. Mechanical strain adds both scalar $\phi_{\varepsilon}$ and vector $\textbf{A}$ gauge potentials to the transistor's Hamiltonian. These potentials create a rich spectrum of quantum interferences in $G$, which can be described as a mechanical Aharonov-Bohm effect. The charge carriers' quantum phase can be controlled by purely mechanical means. For instance, a full 2$\pi$ phase shift can be induced in a (12,9) tube by a 0.7 $\%$ strain change. This work opens opportunities to add quantitative quantum transport strain effects to the tools box of quantum technologies based on 2D materials and their nanotubes.

cond-mat.mes-hall↗

arXiv2024

Exotic thermoelectric properties of coronene-cyclobutadienoid graphene nanoribbons

Thermoelectric materials traditionally incorporate heavy metals to achieve low lattice thermal conductivity. However, elements such as Te, Bi, and Pb are costly and pose environmental hazards. In this study, we introduce a novel design strategy for thermoelectric materials, focusing on room-temperature, light-element, and high-ZT materials such as coronene-cyclobutadienoid graphene nanoribbons (cor4GNRs). This material demonstrates a ZT value exceeding 2.1, attributed to its exceptionally low phonon thermal conductivity resulting from its unique edge structure. Importantly, its electrical conductance and Seebeck coefficient remain relatively high and nearly unaffected by the edge structure. This distinct behavior in phonon and electronic transport properties leads to a remarkably high ZT value. Additionally, we discover that applying strain can significantly reduce phonon thermal conductivity, potentially increasing the ZT value to over 3.0. Our findings provide innovative insights for the design and application of advanced thermoelectric materials.

cond-mat.mtrl-sci↗

arXiv2024

High-field magnetoelectric coupling and successive magnetic transitions in Mn-doped polar antiferromagnet Ni3TeO6

Among the 3d transition metal ions doped polar Ni3TeO6, Mn-doped Ni3TeO6 has stimulated great interest due to its high magnetic ordering temperature and complex magnetic phases, but the mechanism of magnetoelectric (ME) coupling is far from understood. Herein we report our systematic investigation of the chemical control of magnetism, metamagnetic transition, and ME properties of Ni3-xMnxTeO6 single crystals in high magnetic field (H) up to 52 T. We present a previously unreported weak ferromagnetic behavior appeared in the ab plane below 9.5 K in addition to the incommensurate helical and commensurate collinear antiferromagnetic states. In the low-field region, a spin-flop type metamagnetic transition without any hysteresis occurs at Hc1 for H // c, while another metamagnetic transition accompanied with a change in electric polarization is observed at Hc2 in the high-field region both for H // c and H // ab above 30 K, which can be attributed to the sudden rotation of magnetic moments at Ni2 sites. The ME measurements reveal that a first-order ME effect is observed in the low-T and low-H regions, while a second-order ME coupling term appears above 30 K in the magnetic field range of Hc1 < H < Hc2 for H // c and H < Hc2 for H // ab, both becoming significant with increasing temperature. Eventually, they are dominated by the second-order ME effect near the antiferromagnetic transition temperature. The present work demonstrates that Ni3-xMnxTeO6 is an exotic magnetoelectric material compared with Ni3TeO6 and its derivatives, thereby providing insights to better understand the magnetism and ME coupling in Ni3TeO6 and its derivatives.

cond-mat.mtrl-sci↗

arXiv2024

Magnetic structure and magnetoelectric coupling in antiferromagnet Co5(TeO3)4Cl2

The van der Waals (vdW) layered multiferroics, which host simultaneous ferroelectric and magnetic orders, have attracted attention not only for their potentials to be utilized in nanoelectric devices and spintronics, but also offer alternative opportunities for emergent physical phenomena. To date, the vdW layered multiferroic materials are still very rare. In this work, we have investigated the magnetic structure and magnetoelectric effects in Co5(TeO3)4Cl2, a promising new multiferroic compound with antiferromagnetic (AFM) Neel point TN = 18 K. The neutron powder diffraction reveals the non-coplanar AFM state with preferred Neel vector along the c-axis, while a spin re-orientation occurring between 8 K and 15 K is identified, which results from the distinct temperature dependence of the non-equivalent Co sites moment in Co5(TeO3)4Cl2. What is more, it is found that Co5(TeO3)4Cl2 is one of the best vdW multiferroics studied so far in terms of the multiferroic performance. The measured linear ME coefficient exhibits the emergent oscillation dependence of the angle between magnetic field and electric field, and the maximal value is as big as 45 ps/m. It is suggested that Co5(TeO3)4Cl2 is an appreciated platform for exploring the emergent multiferroicity in vdW layered compounds.

cond-mat.mtrl-sci↗

arXiv2023

Mechanical control of quantum transport in graphene

Two-dimensional materials (2DMs) are fundamentally electro-mechanical systems. Their environment unavoidably strains them and modifies their quantum transport properties. For instance, a simple uniaxial strain could completely turn off the conductivity of ballistic graphene or switch on/off the superconducting phase of magic-angle bilayer graphene. Here we report measurements of quantum transport in strained graphene which agree quantitatively with models based on mechanically-induced gauge potentials. We mechanically induce in-situ a scalar potential, which modifies graphene's work function by up to 25 meV, and vector potentials which suppress the ballistic conductivity of graphene by up to 30 % and control its quantum interferences. To do so, we developed an experimental platform able to precisely tune both the mechanics and electrostatics of suspended graphene transistors at low-temperature over a broad range of strain (up to 2.6 %). This work opens many opportunities to experimentally explore quantitative strain effects in 2DM quantum transport and technologies.

cond-mat.mes-hall↗

arXiv2023

Cosmological constraints from Type I radio-loud quasars

We obtain a new sample of 1192 Type I quasars with the UV-optical, radio and X-ray wavebands coverage by combining \citet{Huang2022} and other matching data of SDSS-DR16 with FIRST, XMM-Newton, and Chandra Source Catalog, and a sample of 407 flat-spectrum radio-loud quasars (FSRLQs) of blazars from the Roma-BZCAT, which can be used to investigate their multi-band luminosity correlations and measure the luminosity distances of these Type I radio-loud quasars (RLQs) samples. We check the correlation between X-ray, UV-optical, and radio luminosity for various groupings of radio-quiet quasars (RQQs) and RLQs by parameterizing X-ray luminosity as a sole function of UV-optical or radio luminosity and as a joint function of UV-optical radio luminosity, which also can be employed to determine these cosmological distances. By Bayesian information criterion (BIC), the data suggest that the X-ray luminosity of RQQs is indirectly correlative with radio luminosity because of the connection between UV-optical and radio luminosity. But for RLQs, the X-Ray luminosity is directly related to radio luminosity, and the correlations between X-ray, optical/UV, and radio luminosity increase with the ratio of monochromatic luminosities logR. Meanwhile, we compare the results from RLQs with different UV-optical power law index ${\Gamma _{UV}}$, the goodness of fit for RLQs with ${\Gamma _{UV}}\le 1.6$ seems to be better. Finally, we apply a combination of Type I RLQs and SN Ia Pantheon to verify the nature of dark energy concerning whether or not its density deviates from the constant, and give the statistical results.

astro-ph.CO↗

arXiv2022

Energy Transfer into Period-Tripled States in Coupled Electromechanical Modes at Internal Resonance

Efficient energy transfer often occurs between oscillation modes in a resonator when they are tuned to internal resonance. We design the eigenfrequencies of two vibrational modes of an electromechanical resonator to be close to a ratio of 3:1 and demonstrate that the energy supplied to the upper mode can be controllably transferred to the lower mode. With the lower mode vibrating with a period tripled that of the upper mode, the discrete time-translation symmetry imposed by the periodic drive is broken. The lower mode settles into one of three stable period-tripled states with different phases. This channel for energy transfer from the upper mode can be turned on or off without changing system parameters. When the upper mode itself becomes multistable under strong resonant or parametric drive, additional sets of coexisting period-tripled states emerge in the lower mode. In the latter case, we measure a total of 6 coexisting vibration states with identical amplitude but phases differing by $π$/3. Excitation of coexisting states with three different phases could open new opportunities in designing mechanical memory based on ternary logic. Coupled resonators with period-tripled states can also be used to model complex interacting systems with spin equals one.

cond-mat.mes-hall↗

arXiv2022

A measure of cosmological distance using the \civ\ Baldwin effect in quasars

We use the anticorrelation between the equivalent width (EW) of the C\,\textsc{iv} 1549 {\AA} emission line and the continuum luminosity in the quasars rest frame (Baldwin effect) to measure their luminosity distance as well as estimate cosmological parameters. We obtain a sample of 471 Type I quasars with the UV/optical spectra and EW (C\,\textsc{iv}) measurements in the redshift range of $2.3< z< 7.1$ including 25 objects at $5 < z < 7.1$, which can be used to investigate the C\,\textsc{iv} Baldwin effect and determine cosmological luminosity distance. The relation $EW(C\,\textsc{iv}) \propto {(\lambda {L_\lambda })^\gamma }$ can be applied to check the inverse correlation between the C\,\textsc{iv} EW and ${L_\lambda }$ of quasars and give their distance, and the data suggest that the EW of C\,\textsc{iv} is inversely correlated with continuum monochromatic luminosities. On the other hand, we also consider dividing the Type I quasars sample into various redshift bins, which can be used to check if the C\,\textsc{iv} EW-luminosity relation depends on the redshift. Finally, we apply a combination of Type I quasars and SNIa Pantheon to test the property of dark energy concerning whether or not its density deviates from the constant, and give the statistical results.

astro-ph.CO↗