Exploring materials with low lattice thermal conductivity is critical for advancing thermal barrier coatings and thermoelectrics. In this work, we reveal the significant influence of antibonding states and higher-order anharmonicity on the thermal transport properties of $M\mathrm{Te}{X}_4$ ($M=\mathrm{Zr}$, Hf; $X=\mathrm{S}$, Se) monolayers. Our results indicate that the valence bands close to the Fermi level in the Te-$X$ bonds exhibit significant antibonding states, which weaken the bonding strength and induce soft optical phonon modes in $M\mathrm{Te}{X}_4$. The softened bonding and phonon modes significantly enhance the phonon anharmonic scattering rates, thereby dramatically reducing the thermal conductivity of $M\mathrm{Te}{X}_4$. Meanwhile, the in-plane vibrational modes with quartic potential wells lead to strong four-phonon scattering, further limiting the thermal transport performance in these materials. Moreover, it is found that the abnormal increase in bond energy within the Hf system gives rise to an unusual mass dependence of thermal conductivity, that is, the thermal conductivity of the heavy atomic system $\mathrm{Hf}\mathrm{Te}{X}_4$ exceeds that of the light atomic system $\mathrm{Zr}\mathrm{Te}{X}_4$. Our results highlight the critical role of antibonding states and higher-order anharmonicity in suppressing thermal transport, and could provide fundamental insights and theoretical guidance for exploring and designing materials with low thermal conductivity.

Quantum processors based on superconducting qubits are being scaled to larger qubit numbers, enabling the implementation of small-scale quantum error-correction codes. However, catastrophic chip-scale correlated errors have been observed in these processors, attributed to, e.g., cosmic ray impacts, which challenge conventional error-correction codes such as the surface code. These events are characterized by a temporary but pronounced suppression of the qubit-energy relaxation times. Here, we explore the potential for modular quantum computing architectures to mitigate such correlated energy decay events. We measure cosmic-ray-like events in a quantum processor comprising a motherboard and two flip-chip bonded daughterboard modules, each module containing two superconducting qubits. We monitor the appearance of correlated qubit decay events within a single module and across the physically separated modules. We find that while decay events within one module are strongly correlated (over $85\mathrm{\%}$), events in separate modules only display approximately $2\mathrm{\%}$ correlations. We also report coincident decay events in the motherboard and in either of the two daughterboard modules, providing further insight into the nature of these decay events. These results suggest that modular architectures, combined with bespoke error-correction codes, offer a promising approach for protecting future quantum processors from chip-scale correlated errors.

Spin fluctuations are an important issue for the design and operation of future spintronic devices. Femtosecond noise-correlation spectroscopy (FemNoC) was recently applied to detect ultrafast magnetization fluctuations. FemNoC gives direct access to the spontaneous fluctuations of magnetization in magnetically ordered materials. In FemNoC experiments, the magnetic fluctuations are imprinted on the polarization state of two independent femtosecond probe pulses upon transmission through a magnetic sample. Using a subharmonic demodulation scheme, the cross-correlation of the signals from both pulse trains is calculated. Here, we quantitatively link the FemNoC output signal to an optical polarization rotation, and then in turn to the magnitude of the inherent spin fluctuations. To this end, three different calibration protocols are presented and compared in accuracy. Ultimately, we quantitatively determine both the variance of optical polarization noise in ${\mathrm{rad}}^2$ and that of the ultrafast magnetization fluctuations in ${(\mathrm{A}/\mathrm{m})}^2$.

We investigate the wave characteristics and homogenization theory of soft-matter layered structures in the low-frequency P-wave limit. Using the potential method, we derive a closed-form dispersion relation and identify three distinct wave modes: quasistatic, resonance, and slip. These modes are governed by equivalent interface conditions—namely, a continuous interface for the quasistatic mode, a springlike interface for the resonance mode, and a sliplike interface for the slip mode. Furthermore, we propose a simplified model that captures P-wave characteristics in the high-frequency S-wave regime. Our findings provide a unified framework for wave–structure interactions across solids, liquids, and soft-matter composites, enabling predictive design of metamaterials with programmable wave responses. This study offers insight into the fundamental understanding of layered media and provides direct design principles for applications in acoustic cloaking, vibration damping, and biomedical imaging.

Conventional chamber silencers are limited by their narrow operational bandwidth. To overcome this limitation, we propose and investigate a metamaterial chamber silencer that integrates a side-loaded acoustic metamaterial array within a contraction or expansion chamber. Through a combination of theoretical modeling and experimental validation, we demonstrate that the strategic placement of the metamaterial units is crucial to achieve broadband sound attenuation. A prototype is fabricated and tested, exhibiting a transmission loss greater than 10 dB across a 2.7-octave bandwidth (500–3300 Hz) while maintaining 50% of the baseline airflow velocity. The underlying physical mechanism for this ultrabroadband performance originates from a synergy between global destructive wave interference and localized resonant dissipation. Our work presents a systematic design methodology for compact, high-performance metamaterial chamber silencers with significant potential for practical applications in industrial duct systems where both substantial noise reduction and high-speed airflow are required.

This work provides a detailed mapping of various mechanisms of surface-trap-induced gate leakage in $\mathrm{Ga}\mathrm{N}$ HEMTs across a temperature range from room to cryogenic levels. Two-dimensional variable-range hopping is observed at small gate bias. Under higher reverse gate bias, the leakage is dominated by the Poole-Frenkel emission above 220 K, but gradually transitions to the trap-assisted tunneling below 220 K owing to the frozen-trap effect. The trap barrier height extracted from the gate leakage current under the upward gate sweep is 0.65 V, which is 12% higher than that from the downward sweep. The gate leakage current as a function of the gate bias exhibits clockwise hysteresis loops above 220 K but counterclockwise ones below 220 K. This remarkable opposite hysteresis phenomenon is thoroughly explained by the trap mechanisms.

Exotic and controllable collective magnetic excitations in a chiral helimagnet ${\mathrm{Cr}\mathrm{Nb}}_3{\mathrm{S}}_6$ make it an ideal candidate for exploring emergent electromagnetic phenomena and developing magnon-based devices. Here, we experimentally investigate the polarization properties of the magnetic excitations in a ${\mathrm{Cr}\mathrm{Nb}}_3{\mathrm{S}}_6$ single crystal using circular polarization resolved spectroscopy. An external magnetic field controlled the magnetic structure from a chiral soliton lattice (CSL), consisting of chiral soliton kinks and ferromagnetic domains, to the forced ferromagnet (FFM) phase, and conventional and circular dichroism microwave spectra are observed over a wide frequency range. The observed magnetic excitations, including a CSL phonon mode, Kittel-like mode, and band structures likely due to the excitation of magnetostatic waves, are well characterized by distinct polarization properties. These results visualize the local spin dynamics in the CSL and the influence of the Dzyaloshinskii–Moriya interaction in the FFM phase, aiding the fundamental understanding of the spin dynamics in chiral helimagnets.

In this work, we investigate the electronic structure and interfacial band alignment of β-$({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3/{\mathrm{Ga}}_2{\mathrm{O}}_3$ heterojunctions using a combination of synchrotron-based hard x-ray photoemission spectroscopy (HAXPES) and first-principles hybrid density functional theory calculations. β-$({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3$ films with $\mathrm{Al}$ compositions of x = 0.12, 0.19, and 0.29 were grown on $\mathrm{Fe}$-doped β-${\mathrm{Ga}}_2{\mathrm{O}}_3$ (010) substrates via pulsed laser deposition. The band gap of β-$({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3$ increases from (4.83 ± 0.05) eV (x = 0) to (5.37 ± 0.08) eV (x = 0.29), primarily driven by an upward shift of the conduction band edge due to hybridization between $\mathrm{Al}$ 3s and $\mathrm{Ga}$ 4s states, while the valence band edge exhibits a slight downward shift. Both experimental HAXPES data and theoretical calculations confirmed the formation of a “type I” (straddling) band alignment in the β-$({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3/{\mathrm{Ga}}_2{\mathrm{O}}_3$ heterojunctions. For instance, at x = 0.29, the conduction band offset and valence band offset are approximately 0.33 and 0.21 eV, respectively. These findings provide valuable insights for designing modulation-doped β-$({\mathrm{Al}}_x{\mathrm{Ga}}_{1-x}{)}_2{\mathrm{O}}_3/{\mathrm{Ga}}_2{\mathrm{O}}_3$ heterostructures, enabling the realization of a two-dimensional electron gas and its application in high-frequency electronic devices.

Josephson junctions formed in semiconductor nanowires host Andreev bound states and serve as a physical platform to realize Andreev qubits tuned by electrostatic gating. With the Andreev bound state being confined to the nanoscale weak link, it couples to a circuit-QED architecture via the state-dependent supercurrent flowing through the weak link. Thus, increasing this coupling strength is a crucial challenge for this architecture. Here, we demonstrate the fabrication and microwave characterization of a weak link which is defined in an $\mathrm{In}\mathrm{As}$-$\mathrm{Al}$ (core-half shell) nanowire and embedded in a superconducting loop with a lumped-element resonator patterned from a thin $\mathrm{Nb}\mathrm{Ti}\mathrm{N}$ film with high kinetic inductance. We investigate several devices with various weak-link lengths and performed spectroscopy that revealed pair transitions and single-quasiparticle transitions arising from spin-orbit-split Andreev bound states. Our approach offers a compact geometry and a large resonator impedance above $12\mathrm{k}\mathrm{\Omega }$ at a resonator frequency of 8 GHz, which facilitates large coupling in the system. For the pair transitions, the experimentally observed energy level splitting demonstrates the coupling to an Andreev level of 490 MHz. We apply a perturbative model that shows good agreement with the experimental data and extract the maximum coupling of 968 MHz. Moreover, we show that the coupling is even stronger to an Andreev level with a higher transmission. In addition, spectroscopy of single-quasiparticle transitions reveals spin-orbit-split Andreev bound states with the extracted spin-photon coupling of 77 MHz.

We have developed and tested an efficient mathematical model for calculating a coherent population trapping (CPT) resonance in a periodically modulated laser field when the modulation frequency $f$ is close to the fractional part of the hyperfine splitting frequency (HFS) in the ground state ${\mathrm{\Delta }}_{\mathrm{HFS}}/N$ (where $N=1,2,3,\dots$). In such a polychromatic light, only two frequency components that are most resonant with the working optical transitions in the atom are taken into account exactly, while all other off-resonant frequency components are taken into account by using the second-order perturbation theory in the field magnitude. Within the framework of our concept, an equation for the atomic density matrix is obtained, in which all off-resonant frequency components are described by two operators (which are nondiagonal in the general case): a shift operator and a relaxation operator. This model has been verified by numerical calculations for various dependencies, in which we have not found visual differences from the results of exact calculations. Thus, in our bichromatic model, the infinite variety of periodically modulated fields in CPT spectroscopy can be uniformly described by only five parameters. In addition to a significant mathematical simplification, our model provides a clear physical picture of the various features of CPT spectroscopy in a periodically modulated laser field, including some effects that have not yet been discussed in the scientific literature. In particular, we show a widespread viewpoint that the CPT resonance shift is determined by standard ac Stark shifts of the lower levels is, in general, fundamentally incorrect, since the contribution to the light shift due to beats at the frequency ${\mathrm{\Delta }}_{\mathrm{HFS}}$ between different off-resonant frequency components can be comparable to the value of standard ac Stark shift (or even dominate it). Therefore, even if we have detailed information on the spectral composition of the modulated field (e.g., using a spectrum analyzer), this is, in general, absolutely insufficient for determining the light shift of the CPT resonance.

State-of-the-art classical optimization solvers set a high bar for quantum computers to deliver utility in this domain. Here, we introduce a quantum-preconditioning approach based on the quantum approximate optimization algorithm. This transforms the input problem into a more suitable form for a solver, with the level of preconditioning determined by the depth of the quantum circuit. We demonstrate that best-in-class classical heuristics such as simulated annealing and the Burer-Monteiro algorithm can converge more rapidly when given quantum-preconditioned input for various problems, including Sherrington-Kirkpatrick spin glasses, random $3$-regular graph maximum-cut problems, and a real-world grid energy problem. Accounting for the additional time taken for preconditioning, the benefit offered by shallow circuits translates into a practical quantum-inspired advantage for random $3$-regular graph maximum-cut problems through quantum circuit emulations. We investigate why quantum preconditioning makes the problem easier and test an experimental implementation on a superconducting device. We identify challenges and discuss the prospects for a hardware-based quantum advantage in optimization via quantum preconditioning.

${\mathrm{Ni}\mathrm{Co}}_2{\mathrm{O}}_4$ (NCO), with an inverse spinel structure, stands out for diverse spintronic properties like perpendicular magnetic anisotropy (PMA) and anomalous Hall effect (AHE). Precise control of these properties is essential for ferrimagnetic half-metallic NCO. Here, we report the effective modulation of PMA and AHE in NCO thin films through $\mathrm{Fe}$ doping. We demonstrate that the magnetic anisotropy energy (MAE) reaches $1.03\mathrm{MJ}/{\mathrm{m}}^3$ for ${\mathrm{Ni}\mathrm{Co}}_{1.6}{\mathrm{Fe}}_{0.4}{\mathrm{O}}_4$ films with a robust PMA at room temperature, an order of magnitude enhancement over pristine NCO films and superior to most known PMA-based magnetic structures. A higher Curie temperature can be obtained in ultrathin ${\mathrm{Ni}\mathrm{Co}}_{2-x}{\mathrm{Fe}}_x{\mathrm{O}}_4$ films, compared to the pristine NCO films, due to an enhancement of the superexchange interaction from $\mathrm{Fe}$. We also observe the high tunability of AHE in ${\mathrm{Ni}\mathrm{Co}}_{2-x}{\mathrm{Fe}}_x{\mathrm{O}}_4$ films, with its underlying mechanism undergoing a crossover as x increases, transitioning from extrinsic skew scattering to intrinsic Berry curvature contribution, and finally to a bad-metal-hopping regime. This tunability of AHE is rare in other magnetic systems. These findings provide a pathway for engineering NCO-based ferrimagnetic spintronic platforms with tailored functionalities.

Data exchange across various orbital-angular-momentum (OAM) channels is a crucial interconnection process within mode-multiplexed optical communication networks. However, the versatile cross-connection of multidimensional hybrid channels, especially those involving modes and wavelengths, has been constrained in conventional monochromatic operations, impeding their advancement in multiwavelength systems. Herein, we introduce a selectable mode cross-transformation solution for OAM mode-wavelength hybrid cross-connections by constructing wavelength-dependent rotatable diffractive deep neural networks ($\mathrm{R}\text{−}{\mathrm{D}}^2$NNs). Incorporated with wavelength-sensitive free-space Fresnel diffraction, this framework achieves chromatic dispersion decoupling of three wavelength channels with an 8-nm interval. By deploying spatially engineered rotatable diffractive layers, the $\mathrm{R}\text{−}{\mathrm{D}}^2$NNs unlock switchable unitary transformations for paired OAM modes, allowing for parallel yet independent multimode interconversions across each wavelength dimension, with insertion losses under −5.82 dB and mode purities above 85.8%. As an application demonstration, dynamic data exchange of quadrature phase-shift keying signal streams is successfully implemented by selectively cross-connecting six mode-wavelength multiplexing channels, obtaining bit-error rates close to ${10}^{-5}$. The feasibility of the presented method for both partial and full channel cross-connections under seven static interconnection scenarios is validated and highlighted. Our solutions establish a scalable and miniaturized diffractive network architecture for comprehensive manipulation of both OAM modes and wavelengths, offering a foundational platform for multidimensional channel processing in optical communications and dynamic interconnections.

Photonic topological insulators and self-induced nonreciprocity based on nonlinear effects in asymmetric structures have garnered increased attention due to their potential applications in quantum information technologies and advanced photonic integrated circuits. In this study, we combine these two fields and present asymmetric photonic crystal designs based on all-dielectric checkerboard structures forming topological interfaces. The resulting topological photonic structures lead to the emergence of a narrowband leaky mode in their linear transmission response, accompanied by an edge state with topological protection. The incorporation of the nonlinear optical Kerr effect in the system results in spectral tunability and transmission nonreciprocity in the induced topological edge states, as the input beam intensity is increased, due to the introduction of asymmetric defects along the interface. We envision that the findings presented in our work will lead to tunable photonic topological insulators with a nonreciprocal response that promise to provide new avenues for the development of next-generation photonic devices and quantum optical technologies.

We propose a sequential measurement protocol for accurate low-temperature estimation based on Ramsey interferometry. The resulting correlated outputs significantly enhance the low-temperature precision compared to that of the independent measurement scheme. This enhancement manifests a Heisenberg scaling of the signal-to-noise ratio for small measurement numbers $N$. Detailed analysis reveals that the final precision is determined by the pair correlation of the sequential outputs induced by the low-frequency noise of the thermal sample, which produces a dependence $N^2$ on the signal-to-noise ratio. Remarkably, we find that quantum thermometry within the sequential protocol functions as a high-resolution quantum spectroscopy of the thermal noise, underscoring the pivotal role of the sequential measurements in enhancing the spectral resolution and the temperature-estimation precision. Our methodology signifies the role of the temporal correlation induced by the thermal sample in low-temperature quantum thermometry, which represents an advancement in low-temperature measurement.

Nowadays $\mathrm{Nb}$-based superconducting radio-frequency cavities represent fundamental tools used for (Standard Model) particle acceleration, (beyond Standard Model) particle probing, and long-lifetime photon preservation. We study the superconducting radio-frequency shift in the vicinity of the critical temperature $T_c$ and the quality factor mainly at low temperatures within the Dynes superconductor model. We scrutinize and use the local limit response to the external electromagnetic field. Our approach allows for a finer analysis of the peculiar behavior of the resonant frequency shift immensely close to $T_c$, observed in recent experiments. In several regimes, we analytically elaborate on the width and depth of the resulting dip. Studying the sign of the slope of the resonant frequency shift at $T_c$ in the moderately clean regime clarifies the role of the pair-breaking and pair-conserving disorder. Next, to find the relevance of our description, we compare and also fit our results with the recent experimental data from the $\mathrm{N}$-doped $\mathrm{Nb}$ sample presented by Zarea et al. [Front. Supercond. Mater. 3, 1 (2023)]. Our analysis complies with the experimental findings, especially concerning the dip width. We offer a straightforward, homogeneous-disorder-based interpretation within the moderately clean regime. Comparative analysis for three other cavities with different resonant frequencies reported by Ueki et al. [Prog. Theor. Exp. Phys. 5, 053I02 (2025)] points toward a similar regime. Assuming the same regime at low temperatures, we address details of the high-quality plateaus. Summing all up, this work presents (and studies the limits of) the simple, effective description of the complex problem corresponding to the electromagnetic response in the superconductors, combining homogeneous conventional pairing and two different kinds of disorder scattering.