Two-dimensional (2D) materials have emerged as promising candidates for next-generation electronic and optoelectronic devices due to their high mobility, good electrostatics, and strong light-matter interaction. The 2D oxides are featured by their superior air stability and wide bandgaps, but their applications in high-performance p-type field-effect transistors (FETs) and photodetectors are lacking a systematic and detailed evaluation. In this work, we perform high-throughput screening of binary 2D oxides and identify five candidates with significant potentials for low-power logic devices, high-response ultraviolet (UV) photodetectors, polarizers, and high-k gate dielectrics. These 2D oxide candidates exhibit exceptionally high on-state ($I_{\mathrm{on}}$) current for p-type FETs at a 5-nm gate length region and excellent responsivity for UV photodetectors, outperforming the majority of the reported 2D materials. Our findings provide theoretical insights that address challenges in expanding the applicability of 2D oxides in advanced electronic and optoelectronic device technology beyond the current complementary metal-oxide-semiconductor technology.

Experimental studies of low-frequency underwater acoustic metamaterials are constrained by the need for large-scale three-dimensional anechoic environments. The lack of rigid boundaries in water further impedes the construction of planar waveguides, limiting experimental progress in characterizing such structures. Here, we propose a shallow-water waveguide with hybrid boundaries, combining the natural soft water-air interface with an absorbing bottom layer. A theoretical model based on the Helmholtz equation is developed to analyze wave propagation under three types of boundary conditions: rigid-rigid, soft-soft, and soft-absorbing. Analytical results reveal that the soft-absorbing configuration exhibits mixed propagation characteristics of the other two, which also makes it suitable for quasi-two-dimensional measurements. Numerical simulations are carried out to characterize the resulting sound field, and water-tank experiments confirm the formation of expected propagation modes using a single cylindrical source. Finally, underwater measurements of both periodic cylindrical arrays for acoustic scattering and the designed two-bit coding metasurface for axial focusing show good agreement with theoretical predictions and simulations, validating the effectiveness of the testing platform. This proposed shallow-water waveguide with hybrid boundaries provides a compact and practical solution for underwater acoustic measurements, particularly in the low-frequency regime.

We present a theoretical investigation of van der Waals heterostructures composed of out-of-plane doped $X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ monolayers (X = $\mathrm{S},\mathrm{Se}$) coupled with ${\mathrm{WTe}}_2$, ${\mathrm{Tc}\mathrm{Te}}_2$, ${\mathrm{Al}\mathrm{P}}_3$, or ${\mathrm{In}\mathrm{P}}_3$ for efficient overall water splitting via a direct Z-scheme mechanism. First-principles calculations reveal that ${\mathrm{WTe}}_2/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ and ${\mathrm{Tc}\mathrm{Te}}_2/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ exhibit high solar-to-hydrogen (STH) efficiencies, reaching up to 25.88%. However, thermodynamic analysis indicates that both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) remain energetically unfavorable. In contrast, ${\mathrm{Al}\mathrm{P}}_3/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ and ${\mathrm{In}\mathrm{P}}_3/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ heterostructures demonstrate more balanced photocatalytic behavior, achieving STH efficiencies of up to 31.95%, while the HER can be driven spontaneously. Moreover, cocatalysts are necessary for driving the OER, needing external energies of 0.94 and 1.79 eV for ${\mathrm{In}\mathrm{P}}_3/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ heterostructures. Furthermore, nonadiabatic molecular dynamics simulations reveal rapid interfacial electron-hole recombination in the ${\mathrm{Tc}\mathrm{Te}}_2/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ heterostructure, suggesting enhanced charge separation and transport pathways in the $Z$-scheme configuration. This study highlights the potential of heterostructure engineering combined with out-of-plane doping as a versatile strategy to optimize $\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$-based photocatalysts, and identifies ${\mathrm{In}\mathrm{P}}_3/X@\mathrm{g}$-${\mathrm{C}}_3{\mathrm{N}}_4$ as promising candidates for high-efficiency solar-driven water splitting.

Achieving deterministic placement of self-assembled quantum dots (QDs) during epitaxial growth is essential for the reliable and efficient fabrication of high-quality single-photon sources and solid-state cavity quantum electrodynamics (cQED) systems, yet it remains a significant challenge, owing to the inherent stochasticity of QD nucleation processes. In this work, we theoretically and numerically demonstrate that deterministic QD nucleation within a pristine growth region, e.g., $\mathrm{In}\mathrm{As}$ on a (001)-oriented $\mathrm{Ga}\mathrm{As}$ substrate, can be achieved by engineering the boundary geometry of that region. During epitaxial growth, adatoms initially move toward the boundary and promote the formation of primary QDs along the boundary, driven by curvature and diffusion anisotropy. The resulting primary QD distribution will generate many-body interactions that dynamically reshape the chemical potential landscape for subsequently deposited adatoms, enabling the formation of secondary QDs within the pristine growth region. These findings provide a theoretical foundation for reliable patterning of high optical-quality QDs, with potential applications in next-generation quantum photonic devices.

We present a compact design for a dual-beam Zeeman slower, optimized for efficient production of cold-atom applications. Traditional single-beam configurations face challenges from substantial residual atomic flux impacting downstream optical windows, resulting in increased system size, atomic-deposition contamination, and a reduced operational lifetime. Our approach employs two oblique laser beams and a capillary-array collimation system to address these challenges while maintaining efficient deceleration. For rubidium (${}^{87}\mathrm{Rb}$), simulations demonstrate a significant increase in the fraction of atoms captured by a two-dimensional magneto-optical trap and nearly eliminate contamination of the optical windows by atoms, all within a compact Zeeman-slower length of around $44$ cm. Experimental validation with $\mathrm{Rb}$ and $\mathrm{Yb}$ demonstrates highly efficient atomic loading within the same compact design. This advancement represents a substantial improvement for high-flux cold-atom applications, providing reliable performance for high-precision metrology, quantum computation, and simulation.

The Bennett-Brassard 1984 (BB84) protocol is one of the simplest protocols for implementing quantum key distribution (QKD). In the protocol, the sender and the receiver iteratively choose one of two complementary measurement bases. Regarding the basis choice by the receiver, a passive setup has been adopted in a number of its implementations, including satellite QKD and time-bin encoding. However, conventional theoretical techniques to prove the security of the BB84 protocol are not applicable if the receiver chooses their measurement basis passively, rather than actively, with a biased probability, followed by measurement with threshold detectors. Here we present a fully analytical security proof against coherent attacks for such a decoy-state BB84 protocol with the receiver’s passive basis choice and measurement with threshold detectors. Numerical simulations under practical situations show that the difference in secure key rate between the active and passive implementations of the protocol is negligible except for long communication distances.

Scaling superconducting quantum processors to large qubit counts faces challenges in control-signal delivery, thermal management, and hardware complexity, particularly in achieving microwave signal multiplexing and long-distance quantum information routing at millikelvin temperatures. We propose a space-time modulated Josephson-junction metasurface architecture to generate and multiplex microwave control signals directly at millikelvin temperatures. Theoretical and numerical results demonstrate the generation of multiple frequency tones with controlled parameters, enabling efficient and scalable qubit control while minimizing thermal loads and wiring overhead. We derive the nonlinear wave equation governing this system, simulate beam steering and frequency conversion, and discuss the feasibility of experimental implementation. These results lay the groundwork for a next-generation cryogenic signal-delivery paradigm that may enable scaling of superconducting quantum processors to thousands of qubits without overwhelming limited dilution-refrigerator cooling power.

Reservoir computing has proven effective for tasks such as time-series prediction, particularly in the context of chaotic systems. However, conventional reservoir-computing frameworks often face challenges in achieving high prediction accuracy and adapting to diverse dynamical problems due to their reliance on fixed-weight structures. A concept of an attention-enhanced reservoir computing has been proposed, which integrates an attention mechanism into the output layer of the reservoir-computing model. This addition enables the system to prioritize distinct features dynamically, enhancing adaptability and prediction performance. In this study, we demonstrate the capability of the attention-enhanced reservoir computing to learn and predict multiple chaotic attractors simultaneously with a single set of weights, thus enabling transitions between attractors without explicit retraining. The main result shows that the attention-enhanced reservoir computing is able to distinguish different attractors just by learning from time-series samples. The method is validated using benchmark tasks, including the Lorenz system, the Rössler system, the Hénon map, the Duffing oscillator, and the Mackey-Glass delay-differential equation. Our results indicate that the attention-enhanced reservoir computing achieves superior prediction accuracy, valid prediction times, and improved representation of spectral and histogram characteristics compared to traditional reservoir-computing methods, establishing it as a robust tool for modeling complex dynamical systems.

Parametric modulation, valued for its versatility, is widely employed in superconducting circuits for quantum simulations and high-fidelity two-qubit gates. Conventionally, the qubit coupling strength is determined by the amplitude of the parametric flux pulse, which affects the qubit parameters dramatically. In this paper, we propose and implement a phase-modulation scheme to tune the interaction strength via adjustment of the relative phase between the parametric flux pulses applied to two coupled qubits. We characterize this modulation for sideband couplings, at both sweet and off-sweet spots, achieving a broad range of coupling strengths, as confirmed by both population dynamics and spectroscopy methods. This approach enables phase-controlled modulation of coupling strength, providing a promising candidate for parametrically driven quantum simulations and gate operations.

Amorphous semiconductors are important channel semiconductors in thin-film transistors (TFTs), which serve not only active-matrix displays, but also flexible electronics for Internet of things applications. Nevertheless, a great limitation of amorphous semiconductors is their low carrier mobilities relative to their monocrystalline counterparts. Based on a recently established band-fluctuation framework [Y. Luo and A. Flewitt, Phys. Rev. B 109, 104203 (2024)], this paper shows that the intrinsic carrier mobility of amorphous semiconductors can significantly increase simply through device downscaling, without any material-level optimizations. Specifically, it is revealed that the intrinsic electron mobility of hydrogenated amorphous silicon in a 10-nm-long gap can increase by about 12 times, and this does not compromise device-to-device uniformity. This mobility improvement is a result of reduced localized band-tail states due to the ultrashort gap length relative to the band-fluctuation length scale before downscaling; the latter is determined by the short- and medium-range structural order of the amorphous semiconductor.

Decoherence is a major challenge for quantum technologies, whose negative effects can be mitigated by quantum optimal control. The decoherence dynamics significantly varies depending on the characteristics of the system’s environment, consequently affecting the optimization outcomes. In this work, we investigate the optimization of a negatively charged nitrogen-vacancy (${\mathrm{NV}}^{-}$) center qubit-spin-inversion control pulse, and observe two error-compensation mechanisms, depending on how long the correlation time is compared to the pulse duration. Additionally, we analyze the effects of control space constraints and optimization options to identify a strategy to improve the optimization performance. Finally, we present experimental realizations of the optimized pulses, exhibiting the applicability of the procedure. Our work serves as a generic yet essential guide to implementing optimal control in the presence of realistic noise.

Efficient coupling between quantum emitters and optical cavities is essential for scalable quantum photonic technologies. Group-IV vacancy centers in diamond, particularly the negatively charged tin-vacancy center, have emerged as promising candidates due to their spectral stability, high Debye-Waller factor, and large orbital splitting in ground states. Here, we demonstrate controlled coupling of a single negatively charged tin-vacancy center hosted in a nanodiamond to a fully tunable Fabry-Pérot microcavity. At cryogenic temperatures, we access the weak-coupling regime and observe a transition from the bad-emitter regime to the bad-cavity regime as the optical transition of the color center narrows. At 4 K, a Purcell factor exceeding 1.7 is measured, confirming cavity-enhanced emission. The obtained results demonstrate the potential of $\mathrm{Sn}\text{−}{V}^{-}$ centers in nanodiamonds as a coherent single-photon source for quantum networks.

The integration of elementary quantum objects (atoms, molecules, and quantum dots) with solid-state nanostructures lies at the forefront of nano-optics, nanophotonics, and quantum information science. However, the advancement of this field is hindered by the lack of a rigorous and feasible theoretical framework for describing atom-nanostructure interactions, which are inherently complex and multiparametric. In this work, we develop a theory of light transmission through a zero-mode waveguide (ZMW) containing a single atom. It is shown that the presence of a single atom inside the ZMW can lead to either a significant enhancement or suppression of light transmission, depending on the detuning of the excitation field frequency from the atomic resonance. This extraordinary transmission and blocking effect can be employed for studying the spatiotemporal dynamics of atoms in complex nanoscopic environments, probing quantum optical phenomena, and developing novel nano-optical devices.

We demonstrate a pump-probe strobe light spectroscopy for sensitive detection of magneto-optical dynamics in the context of hybrid magnonics. The technique uses a combinatorial microwave-optical pump-probe scheme, leveraging both the high-energy resolution of microwaves and high-efficiency detection using optical photons. In contrast with conventional stroboscopy using continuous-wave light, we apply microwave and optical pulses with varying pulse widths, and demonstrate magneto-optical detection of magnetization dynamics in ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ films. The detected magneto-optical signals depend strongly on the characteristics of both the microwave and the optical pulses, as well as their relative time delays. We show that good magneto-optical sensitivity and coherent stroboscopic character are maintained, even at a microwave pump pulse of 1.5 ns and an optical probe pulse of 80 ps, under a 7 MHz clock rate, corresponding to a pump-probe footprint of approximately $1\mathrm{\%}$ in one detection cycle. Our results show that time-dependent strobe light measurement of magnetization dynamics can be achieved in the gigahertz frequency range under a pump-probe detection scheme.

Noise resilience of quantum information processing is a crucial precondition to reach the fault-tolerance threshold. While resilience to many types of noise can be achieved through suitable control schemes, resilience to amplitude noise seems to be elusive within the common harmonic approximation for the bus mode of trapped ions. We show that weak anharmonicities admit control schemes that achieve amplitude-noise resilience consistent with state-of-the-art experimental requirements and that the required anharmonicities can be achieved with current standards of microstructured traps or even the intrinsically anharmonic Coulomb interaction. This approach applies broadly to any platform that employs a bosonic bus as a qubit coupler.

We propose a machine-learning-based approach enhanced by quantum reservoir computing (QRC) to estimate the zero-time second-order correlation function $g^{(2)}(0)$. Typically, measuring $g^{(2)}(0)$ requires single-photon detectors and time-correlated measurements. Machine learning may offer practical solutions by training a model to estimate $g^{(2)}(0)$ solely from average intensity measurements. In our method, emission from a given quantum source is first processed in QRC. During the inference phase, only intensity measurements are used, and these are then passed to a software-based decision-tree ensemble model. We evaluate this hybrid quantum-classical approach across a variety of quantum optical systems and demonstrate that it provides accurate estimates of $g^{(2)}(0)$. We further extend our analysis to assess the ability of a trained model to generalize beyond its training distribution, both to the same system under different physical parameters and to fundamentally different quantum sources. While the model may yield reliable estimates within specific regimes, its performance across distinct systems is generally limited.

Irreversible cyclic strain and stress in battery electrodes during ion intercalation or deintercalation drives mechanical energy dissipation, accelerating lifecycle degradation. However, the lack of quantitative methods to assess this dissipation hinders a mechanistic understanding of mechanical behavior in electrochemical systems. Here, we present a theoretical framework integrated with operando strain measurements to quantify stress and strain energy evolution in practical heterogeneous composite electrodes, validated using a ${\mathrm{VO}}_2$-based zinc-ion battery cathode. Under assumptions of plane stress and elastic deformation, spatially resolved stress distributions and average stress or strain energy per cycle are derived and calculated for ${\mathrm{VO}}_2$-based cathodes during dynamic ${\mathrm{Zn}}^{2+}$ insertion or extraction. Experimental validation reveals that biphasic ${\mathrm{VO}}_2$ exhibits lower stress or strain energy magnitude than single-phase ${\mathrm{VO}}_2$ during prolonged cycling, correlating with its superior cycling stability.

Spins in solids and molecules are promising for applications of quantum sensing technology. The sensitivity of quantum sensing depends on how precisely spin observables can be determined in the measurement and is intrinsically limited by the uncertainties of the observables. The use of a spin-squeezed state in a quantum sensor can reduce the uncertainty below the standard quantum limit when combined with an appropriate measurement procedure. Here, we discuss a simulation study of the generation of a squeezed state in an interacting spin system. We show that a spin system coupled via the magnetic dipole interaction can create a squeezed state. Model systems to realize the spin squeezing experimentally are also discussed. In addition, we find that a squeezed state is a type of entangled state. The present work paves the way to realizing a squeezed state using a spin system to build a quantum sensor network with improved sensitivity and to use it for the detection of quantum entanglement.