We report a distributed-feedback behavior in electron-driven dielectric gratings, arising from intrinsic forward-backward wave interactions, relevant to low-threshold coherent emission. Coupled-mode analysis reveals a quasi-stable region in the groove-depth dependence of the distributed-feedback coupling, consistently beginning at a fundamental organ-pipelike resonance. When driven by an electron beam, the guided power exhibits a corresponding resonance landscape, with a peak at the fundamental organ-pipelike resonance followed by regrowth in the quasi-stable region, highlighting a strong correlation between the intrinsic distributed-feedback behavior and electron-surface mode interaction. Based on this framework, we numerically demonstrate a silicon-grating chip-scale distributed-feedback Cherenkov free-electron laser operating in the terahertz (THz) regime and employing a micrometer-scale grating with an optimized groove depth. Small-signal and coupled-mode analyses for the optimized structure predict a milliampere-level oscillation threshold in good agreement with particle-in-cell simulations, while time-domain simulations confirm Bragg-resonant field buildup at 0.328 THz via electron microbunching with sustained guided-field growth along the grating. These results establish a general design principle for low-threshold terahertz sources based on distributed-feedback surface-mode resonances.

Spin qubits in semiconducting quantum dots are currently limited by slow readout processes, which are orders of magnitude slower than gate operations. In contrast, Andreev spin qubits benefit from fast measurement schemes enabled by the large resonator couplings of superconducting qubits but suffer from reduced coherence during qubit operations. Here, we propose fast and high-fidelity measurement protocols based on an electrically tunable coupling between quantum dot and Andreev spin qubits. In realistic devices, this coupling can be made sufficiently strong to enable high-fidelity readout well below microseconds, potentially enabling mid-circuit measurements. Crucially, the electrical tunability of our coupler permits to switch it off during idle periods, minimizing crosstalk and measurement back-action. Our approach is fully compatible with germanium-based devices and paves the way for scalable quantum computing architectures by leveraging the advantages of heterogeneous qubit implementations.

Plasmonic nanobubbles are extensively employed in many fields owing to their distinctive optical and photothermal properties. The mechanisms behind nanobubble formation have attracted growing attention. This work proposes a model combined with the Lattice Boltzmann method and multilayer Mie theory to observe the transient optical and photothermal behaviors during nanobubble formation. The thermoplasmonic effect of gold nanoparticles reduces the density of the surrounding water, generating a spatiotemporally varying refractive index field. In this condition, it is found that for nanoparticles with a 60 nm diameter, the decline in absorption cross section during nanobubble growth leads to prolonged nucleation time. Moreover, the influence of the electric field force acting on water molecules within the plasmonic near-field on nanobubble growth dynamics is investigated. The anisotropic growth of nanobubbles in plasmonic-enhanced nonuniform local electric fields is revealed. Subsequently, rational regulation strategies are designed, including ${\mathrm{SiO}}_2$ coating of nanoparticles and adjustment of incident light polarization modes, which enable precise control of the dimensional anisotropy of nanobubble thickness while maintaining the particle structural integrity. Our work provides a feasible approach for the precise regulation of nanobubble growth and mechanical effects.

Graphene nanoribbon (GNR) emerges as an exceptionally promising channel candidate due to its tunable sizable band gap (0–3 eV), ultrahigh carrier mobility (up to $4600{\mathrm{cm}}^2{\text{V}}^{-1}{\text{s}}^{-1}$), and excellent device performance (current on-off ratio of ${10}^7$). However, the asymmetry of reported $n$-type and $p$-type GNR field-effect transistors (FETs) at ultrashort gate length $(L_{\mathrm{g}})$ has become an obstacle to future complementary metal-oxide-semiconductor (CMOS) integration. Here, we conduct ab initio quantum transport simulations to investigate the transport properties of sub-5-nm $L_{\mathrm{g}}$ 7-armchair-edge hydrogened GNR (7 AGNRH) FETs. The on-state current, delay time, and power dissipation of the $n$-type and $p$-type 7 AGNRH FETs fulfill the International Technology Roadmap for Semiconductors targets for high-performance devices when $L_{\mathrm{g}}$ is reduced to 3 nm. Remarkably, the 7 AGNRH FETs exhibit superior $n$-type and $p$-type symmetry to the 7-9-7 AGNRH FETs due to the more symmetrical electron and hole effective masses. Compared with the monolayer ${\mathrm{MoS}}_2$ and ${\text{MoTe}}_2$ counterparts, the 7 AGNRH FETs have better device performance, which could be further improved via gate engineering. Our results shed light on the immense potential of 7 AGNRH in advancing CMOS electronics beyond silicon.

We present a superconducting qubit, which consists of two strongly coupled modes: one for data storage and one for coupling, allowing faster, higher-fidelity entangling gates and readout. The use of a dedicated coupling mode allows nonlinear couplings of several hundred MHz between the data mode and other elements, with minimal linear coupling to the data mode. Including decoherence, simulations show that this architecture enables microwave-only cz gates with an infidelity of $8.7\times {10}^{-5}$ in 17 ns and always-on $ZZ$ interaction less than 0.4 kHz. Numerical simulations also show readout with state assignment error of $1\times {10}^{-3}$ in 38 ns (assuming quantum efficiency $\eta =0.5$). Our readout scheme naturally reduces Purcell decay to negligible levels without a Purcell filter and provides a mechanism to suppress shot noise dephasing times to the 10 ms level when not performing readout. Single-qubit gate infidelities are below $1\times {10}^{-5}$ including decoherence. These beyond experimental state-of-the-art gate and readout fidelities rely only on capacitive coupling between arm qubits, making the arm qubit a promising scalable building block for fault-tolerant quantum computers.

Exciplex-based organic light-emitting diodes (EX-OLEDs) include interfacial- and bulk-heterojunction devices, and the external quantum efficiency (EQE) of the bulk device is typically higher than that of the interfacial one when fabricated with the same donor and acceptor materials. Although photoluminescence (PL) and transient PL were used to find that this higher EQE is attributed to the enlarged electron-hole recombination zone, its further reasons are still vague. Here, organic magnetic field $(B)$ effects (OMFEs), including magneto-electroluminescence (MEL), magneto-conductance (MC), and magneto-efficiency ($\mathrm{M}\eta$), are used to find new reasons for the improved EQE. Specifically, low-field effects ($|B|\le 10\mathrm{mT}$) of both MEL and $\mathrm{M}\eta$ traces from the interfacial and bulk devices, respectively, show the $B$-mediated intersystem crossing (ISC) and reverse ISC (RISC) features. Furthermore, although both low-field effects of their MC traces exhibit the $B$-mediated ISC feature, the ISC magnitude of the bulk device is lower than that of the interfacial one under the same injection currents. That is, the low-field effects of their OMFE traces reflect that the RISC process from triplet to singlet EX states (${\text{EX}}_3\to {\text{EX}}_1$) in the bulk device is stronger than that in the interfacial one since these low-field effects are determined by the superposition of the $B$-mediated ISC and RISC processes. Moreover, all high-field effects ($10<|B|\le 300\mathrm{mT}$) of their OMFE traces show the $B$-mediated triplet-charge annihilation (TCA) between ${\text{EX}}_3$ and free charges (${\text{EX}}_3+q\to {\text{S}}_0+q^{\prime }$), but the TCA magnitudes of the bulk device are lower than those of the interfacial one under the same injection currents, indicating a weaker TCA process in the bulk device than that in the interfacial one. This is because the enlarged electron-hole recombination zone increases the quantity of the intermolecular contacts between donor and acceptor materials, causing a higher recombination efficiency in the bulk device than that in the interfacial one. The improved recombination efficiency will increase the quantity of ${\text{EX}}_3$ and reduce that of free charges, which results in the enhanced RISC and weakened TCA, respectively. The weakened TCA still increases the quantity of ${\text{EX}}_3$ and then further enhances RISC, leading to the elevated singlet/triplet ratio and the improved device EQE. Therefore, this work not only uses OMFEs to reveal novel physical mechanisms of the higher EQE from the bulk device than that from the interfacial one, but also paves the way for further developing high-efficiency bulk-heterojunction EX-OLEDs.

We present a nonperturbative tensor-network approach to the excitation spectra of superconducting circuits based on Josephson-junction arrays. These arrays provide the large lumped inductances required for qubit designs, yet their intrinsically many-body nature is typically reduced to effective single-mode descriptions. Perturbative treatments attempt to include the collective array modes neglected in these approximations, but a fully nonperturbative analysis is challenging due to the many-body structure and the collective character of these modes. We overcome this difficulty using the DMRG-X algorithm, which extends tensor-network methods to excited states. Our key advance is a construction of trial states from the linearized mode structure, enabling direct computation of excitations, even in degenerate manifolds, which was previously inaccessible. Our results reveal significant deviations from, and allow us to improve upon, previous perturbative treatments in the regime of low array junction impedance.

As superconducting quantum processors continue to scale, high-performance quantum control becomes increasingly critical. In densely integrated architectures, unwanted interactions between nearby qubits give rise to crosstalk errors that limit operational performance. In particular, direct exchange-type ($\mathit{XY}$) interactions are typically minimized by designing large frequency detunings between neighboring qubits at the hardware level. However, frequency crowding in large-scale systems ultimately restricts the achievable frequency separation. While such $\mathit{XY}$ coupling facilitates entangling gate operations, its residual presence poses a key challenge during single-qubit controls. Here, we propose a scalable pulse-level control framework, incorporating frequency modulation and dynamical decoupling to suppress $\mathit{XY}$ crosstalk errors. This framework operates independently of coupling strengths, reducing calibration overhead and naturally supporting multiqubit connectivity. Numerical simulations show orders-of-magnitude reductions in infidelity for both idle and single-qubit gates in a two-qubit system. We further illustrate scalability in a five-qubit layout, where crosstalk between a central qubit and four neighbors is simultaneously suppressed. Our crosstalk suppression framework provides a practical route toward high-fidelity operation in dense superconducting architectures.

In recent years, several architectures have been proposed for implementing two-qubit operations on fluxonium superconducting qubits. A particularly promising approach, which was demonstrated experimentally by Refs. [L. Ding et al. Phys. Rev. X 13, 031035 (2023), S. Singh et al. Phys. Rev. Appl. 25, 024020 (2026)], employs a transmon superconducting qubit as a tunable coupler between the fluxonium qubits. These experiments have shown that the transmon coupler enables fast, high-fidelity two-qubit operations while suppressing unwanted $ZZ$ crosstalk between the fluxonium qubits. In this work, we numerically study the scalability of this architecture. We find that, when trivially scaling this architecture, crosstalk from spectator qubits limits the gate fidelity to below 90%. We show that these spectator errors can be reduced to below ${10}^{-4}$ by reducing the coupling strength and by dynamically tuning transmons that are not used for a two-qubit operation to an off position. We further investigate the resilience of the operation to direct capacitive coupling between the transmon couplers and to microwave crosstalk.

Surface-acoustic-wave (SAW) resonators are a promising platform for constructing hybrid quantum systems, where confined acoustic waves enable strong interactions with various physical systems. Focusing SAW resonators, which reduce mode volume while suppressing diffraction losses, have recently been investigated for applications in such hybrid systems. However, the resonator leads to additional transverse-mode resonances, which cause undesired responses. In this work, we develop focusing SAW resonators using a thin-film lithium niobate on sapphire. A film thinner than the SAW wavelength allows a highly confined acoustic-wave mode to be localized on the substrate surface. By using contoured electrodes following a two-dimensional Gaussian beam shape, we focus the SAW mode to near the diffraction limit and confirm this focusing via optical imaging. Furthermore, by engineering the spatial mode overlap of the interdigital transducer electrodes, we suppress the excitation of higher-order transverse modes.

Controlled disorder in correlated materials provides a new route to emergent stochastic dynamics in neuromorphic hardware. Here we show that focused ion beam irradiation in ${\text{VO}}_2$- and ${\mathrm{V}}_2{\mathrm{O}}_3$-based resistive-switching oscillators induces a transition from regular periodic oscillations to strongly irregular stochastic firing, while simultaneously reducing the required switching energy by orders of magnitude. Under an applied electric field, these materials undergo a volatile insulator-to-metal transition characterized by the formation of percolating metallic filaments within an insulating bulk. Using numerical simulations based on the Mott resistor network, we demonstrate that defect-induced modifications to filament nucleation and stability drive these devices into stochastic oscillatory regimes. These results are validated by experimental measurements on irradiated ${\text{VO}}_2$ and ${\mathrm{V}}_2{\mathrm{O}}_3$ devices.

Energy dissipation in solids under gigahertz (GHz) vibrations is critical to the performance of advanced devices and materials, for example, in nanoresonators used in quantum information systems. Here, we investigate energy loss from forced vibrations due to phonon scattering and thermalization. Our time-resolved models, based on the full phonon scattering matrix, show that intermode temperature differences compete with the effects of underrelaxed nonequilibrium phonons when the period of the forced oscillations is shorter than the phonon scattering rates, leading to the usual unimodal damping behavior as a function of oscillator frequency. In addition, the Akheizer damping mechanism used with the time-dependent phonon dynamics models captures the damping response in closer agreement with fully atomistic models in the ultrasonic to mid-GHz regime than phonon models that rely on the relaxation time approximation. These findings are shown to generalize to multiple single crystals, including silicon, diamond, and nickel.

We demonstrate high-contrast, edge-enhanced proton imaging using a relativistic hollow Laguerre-Gaussian laser (approximately ${10}^{20}\text{W}/{\text{cm}}^2$) incident on nanometer-scale CH foils. In contrast to conventional Gaussian drive, which produces a dotlike proton source, the Laguerre-Gaussian beam generates a ring-shaped proton beam that preferentially enhances peripheral features and enables high-contrast boundary imaging. As a proof of principle, we obtain a clear outline of low-($Z$) soft tissue in a beetle specimen, benefiting from the strong sensitivity of proton energy loss to modest density variations. By comparison, x-ray radiography in the same geometry primarily emphasizes high-($Z$) components (e.g., skeletal structures). Our results establish Laguerre-Gaussian-laser-driven proton radiography as a promising, complementary modality to x-ray imaging, offering improved soft tissue contrast and potential utility for medical diagnostics and radiotherapy guidance.

Here, we present a proof-of-principle high-dimensional quantum key distribution (QKD) protocol utilizing the position and momentum entanglement of photon pairs. The protocol exploits the fact that position and momentum form mutually unbiased bases, linked via a Fourier transform. One photon of the entangled pair is measured by the sender in a randomly chosen basis—either position or momentum—selected passively via a beam splitter. This projective measurement remotely prepares the partner photon in a corresponding spatial mode, which is sent to the receiver, who similarly performs a random measurement in one of the two bases. In this implementation, we achieve a photon information efficiency of 5.07 bits per photon using 90 spatial modes and a maximum bit rate of $0.9\mathrm{Kb}/\mathrm{s}$ with 361 modes. To assess the scalability of this spatial mode encoding scheme, we theoretically show that using a brighter entangled photon source along with next-generation single-photon cameras—featuring improved quantum efficiency, timing, and spatial resolution—this approach could achieve 9 bits per photon at 2000 spatial modes and a bit rate of over $700\mathrm{Mb}/\mathrm{s}$ at 4400 modes while accounting for finite-key effects. These results quantify the opportunities and performance bounds of spatially encoded, entanglement-based QKD and provide a benchmark for future high-dimensional quantum communication systems.

Interfacial electric fields are widely exploited in heterojunction photocatalysts to promote charge separation. However, conventional type-II heterojunctions inevitably suffer from severe loss of redox potential, while Z-/S-scheme architectures retain strong redox capability only at the expense of substantial carrier consumption. Here, we propose a polarization-driven $\Upsilon$-scheme heterojunction that harnesses two oppositely oriented polarization fields to establish an unconventional charge-transfer pathway. Specifically, polarized Janus monolayers ($\mathrm{M}\text{−}{\mathrm{M}}^{\prime }\text{−}\mathrm{C}\text{−}\mathrm{X}\text{−}{\mathrm{X}}^{\prime }$; $\mathrm{M}/{\mathrm{M}}^{\prime }=\mathrm{Sc}$, Y; $\mathrm{X}/{\mathrm{X}}^{\prime }=\mathrm{F}$, Cl, Br, H) are integrated with ferroelectric MXenes (${\mathrm{M}}_2{\mathrm{CO}}_2$; M $=$ Sc, Y), enabling intralayer electron migration toward high-potential regions and hole migration toward low-potential regions. This mechanism preserves intrinsic redox potentials while suppressing interfacial recombination, thereby facilitating near-complete utilization of photogenerated carriers. Consequently, oxidation and reduction reactions are spatially separated at the surface and interface, respectively. Our strategy resolves the long-standing dilemma between maintaining strong redox potentials and maximizing carrier utilization, offering a robust design principle for next-generation high-efficiency photocatalysts.