In this work, we propose a robust control protocol for achieving high-fidelity control of cat-state qubits. The cat-state qubits are generated in a Kerr nonlinear cavity by a single-photon drive. For high-fidelity control of these qubits, we apply a polychromatic pulse train (PPT), which consists of a sequence of $N$ pulses with different driving amplitudes. By optimizing the parameters of individual pulses in the PPT, errors in the single-photon drive can be suppressed. The ability to suppress such errors can be further enhanced by increasing the pulse-sequence length $N$, albeit at the cost of an extended bit-flip time. Numerical simulations demonstrate that the protocol exhibits strong robustness not only against single-photon drive-strength errors but also against errors in the tunable parameter itself. Furthermore, it maintains high fidelity even under the influence of single-photon losses. We expect that this protocol may provide an effective approach for the robust control of cat-state qubits.

Pauli spin blockade (PSB) is a key paradigm in semiconductor nanostructures that gives access to the spin physics. We report the direct observation of PSB using gate-dispersive reflectometry on double quantum dots in the presence of a finite source-drain bias voltage. The reservoir charge transitions are strongly modulated, turning on and off when entering and leaving the blockaded region, consistent with a simple model. Observed in hole double quantum dots in a $\mathrm{Ge}$/$\mathrm{Si}$ core/shell nanowire and a $\mathrm{Si}$ fin field-effect transistor, the effects are enhanced at larger bias voltage and suppressed by a magnetic field. This work establishes the fundamental dispersive signature of PSB under bias as an emerging tool for probing quantum dot devices.

Doping of ${\mathrm{Hf}}_{0.5}{\mathrm{Zr}}_{0.5}{\mathrm{O}}_2$ ($\mathrm{HZO}$) films with rare-earth metals during atomic layer deposition growth has been found to significantly affect their structural and functional properties. Here, we report on the structural properties of $\mathrm{Y}\text{−}$ and $\mathrm{La}$-doped polycrystalline $\mathrm{HZO}$ films as revealed by synchrotron-based near-edge x-ray absorption fine-structure (NEXAFS) technique, and complemented by x-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques for $\mathrm{Y}:\mathrm{HZO}$. In contrast to XRD and TEM, NEXAFS analysis taken near the $\mathrm{O}$ K (1s)-edge can distinguish between orthorhombic (o-) and tetragonal (t-) phases with much better accuracy and, furthermore, provides quantitative information about phase composition. In addition, the absorption spectra taken near $\mathrm{Zr}$ ${\mathrm{M}}_3$ ($3p_{3/2}$)-edge and $\mathrm{O}$ K (1s)-edge also provide reliable information about the presence of the monoclinic (m-) phase, even in the case of highly textured samples. The structural data are further correlated with the electrical properties of $\mathrm{Y}$: and $\mathrm{La}:\mathrm{HZO}$ films sandwiched in capacitor structures, which are found to depend on the dopant concentration either, suggesting that the delicate balance of different phases in doped $\mathrm{HZO}$ (revealed by NEXAFS) defines the functional properties of devices. Despite the progress in the quantitative assessment of phase composition by NEXAFS, the unambiguous prediction of the electrical response in doped $\mathrm{HZO}$ remains challenging, and calls for the use of operando NEXAFS structural analysis in functional prototype capacitor devices to directly monitor an apparent structural evolution in this class of materials upon the electrical stress.

This study presents an approach that leverages the existing knowledge acquired in one-dimensional BDI class discrete metamaterials, such as mass-spring systems or acoustic resonators, and exploits it to realize fully continuous elastic two-dimensional topological waveguides. The design relies on the concept of evanescently coupled waveguides and defect resonances in order to qualitatively reproduce the equivalent dynamics of prototypical BDI discrete systems, such as the Su-Schrieffer-Heeger (SSH) model. Starting with a continuous plate waveguide based on a periodic distribution of pillars, local resonators and waveguides are created by eliminating selected pillars and by exploiting the concept of point and line defects. The height of selected pillars is adjusted to tune the coupling strength between different resonators. The approach is validated by designing fully continuous elastic analogs of both the SSH chain and ladder systems. Numerical simulations and experimental results confirm the validity of the design by showing the emergence of topological edge modes at the interface of topologically distinct systems. In addition, the edge modes obtained in the elastic analog of the SSH ladder are shown to be Majorana-like modes.

Error mitigation has enabled quantum computing applications with more than a hundred qubits and deep circuits. Many error mitigation methods are noise-aware, relying on a faithful characterization of the noise channels of the hardware. However, fundamental limitations lead to unlearnable degrees of freedom of the underlying noise models when considering qubits. Here, we show how to leverage noncomputational states as an additional resource to learn state-preparation errors in superconducting qubits. This allows one to fully constrain the noise models. We can thus independently and accurately mitigate state-preparation errors, gate errors, and measurement errors. Our proposed method is also applicable to dynamic circuits with midcircuit measurements. This work opens the door to improved error mitigation for measurements, both at the end of the circuit and midcircuit.

Two-dimensional (2D) $\mathrm{Ge}\mathrm{Te}$ exhibits excellent interface compatibility with $\mathrm{Si}/{\mathrm{Si}\mathrm{O}}_2$ substrates, which makes it a promising channel material for field-effect transistors beyond the silicon-based era. A recent study has indicated the viability of the exfoliation of 2D $\mathrm{Ge}\mathrm{Te}$ to monolayer (ML) thickness utilizing liquid-phase methodologies assisted by sonication. This study applies ab initio quantum transport simulations to investigate the device performance limits of sub-5-nm ML $\mathrm{Ge}\mathrm{Te}$ metal-oxide-semiconductor field-effect transistors (MOSFETs). The on-state current, subthreshold swing, switching speed, and power consumption of n- and p-type ML $\mathrm{Ge}\mathrm{Te}$ MOSFETs in both the zigzag and armchair orientations are explored. No significant anisotropy is observed. Along the zigzag and armchair directions, the optimized n-type $\mathrm{Ge}\mathrm{Te}$ transistors can well satisfy the key criteria of the International Technology Roadmap for Semiconductors for high-performance applications at a 3-nm gate length, and for low-power applications at a 5-nm gate length. The performance of the n-type transistor exceeds that of the p-type one. The ML $\mathrm{Ge}\mathrm{Te}$ MOSFETs along the zigzag and armchair directions with gate length of 5 nm possess on-state current levels reaching up to 2452 and 1917 µA/µm, accompanied by corresponding energy-delay products $6.24\times {10}^{-30}$ and $2.35\times {10}^{-29}$ Js/µm, respectively, surpassing many other 2D MOSFETs. Our work demonstrates that ML $\mathrm{Ge}\mathrm{Te}$ as a channel candidate can help push Moore’s law down to the sub-5-nm regime.

Quantum computers may one day enable the efficient simulation of strongly coupled plasmas that lie beyond the reach of classical computation in regimes where quantum effects are important and the scale separation is large. In this article, we take a first step toward efficient simulation of quantum plasmas by demonstrating linear plasma wave propagation on a superconducting quantum chip. Using high-fidelity and highly expressive device-native gates, combined with an error-mitigation technique, we simulate the scattering of laser pulses from inhomogeneous plasmas. Our approach is made feasible by the identification of a suitable local spin model whose excitations mimic plasma waves, and whose circuit implementation requires a lower gate count than other proposed approaches that would require a future fault-tolerant quantum computer. This work opens avenues to study more complicated phenomena that cannot be simulated efficiently on classical computers, such as nonlinear quantum dynamics when strongly coupled plasmas are driven out of equilibrium.

We propose a universal approach based on Hamiltonian inverse engineering to realize a set of parameterized two-qubit gates. This method possesses unique advantages to simultaneous control of transitions among four energy levels, providing a simpler and effective way to construct composite two-qubit gates with fewer operations than traditional methods. Applied to silicon double quantum dots (DQDs), one can realize a one-step fSim gate and a $B$ gate with only one pulse switch. Of note, the method can be further integrated with various optimization theories to enhance gate performance. Based on quantum optimal control theory, we develop a high-fidelity fSim gate scheme with experimentally feasible pulse shapes, featuring an average gate time of 50 ns and a theoretical fidelity of 99.95% in the presence of decoherence and approximation error. By incorporating geometric quantum gate principles, we propose a combined geometric and dynamic fSim gate scheme. Numerical simulations demonstrate that this hybrid scheme exhibits stronger robustness against systematic errors compared to the purely dynamic approach. Our method is generalizable to arbitrary two-qubit physical systems, offering a feasible pathway for rapidly and robustly constructing composite two-qubit gates.

Auxetic metamaterials are commonly thought to exhibit favorable mechanical properties, notably high-energy absorption. Here we investigate disordered metamaterials obtained from random beam networks by optimizing simultaneously auxeticity and the energy absorbed before fracture. By giving different weights to these optimization targets, we demonstrate that the optimal configurations are connected along a Pareto front where high auxeticity implies comparatively low-energy absorption and vice versa. We study the mechanical properties of the resulting metamaterials and characterize the different deformation modes obtained for distinct optimization targets. The simulation and optimization results are validated by comparison with the deformation behavior of additively manufactured samples. Our work provides an illustration of the potentials and limitations of multiobjective optimization in the design of disordered mechanical metamaterials.

Axions are hypothetical particles that provide a compelling solution to two major mysteries in modern physics: the strong CP problem and the nature of dark matter. The plasma haloscope has been proposed as a promising approach for probing the higher-mass regime for dark-matter axions by employing a periodic arrangement of conducting wires. In this work, we introduce an alternative tuning mechanism for such wire-based structures by arranging the wires into a spiral configuration. This design enables continuous frequency tuning of 25% with a single central rotation while maintaining the form factor. It also achieves scanning speeds several times faster than traditional tuning approaches, primarily due to the circular perimeter geometry, making it well suited for solenoidal magnet bores. To validate the concept, we fabricated a prototype cavity with six spiral arms and experimentally demonstrated its feasibility, obtaining frequency tuning in close agreement with numerical simulations.

In hybrid microwave structures based on magnonics (so-called magnon cavities), the energy of the electromagnetic field can be transduced into the energy of magnetostatic spin excitations of a nanomagnet (Kittel magnon). This paper proposes a mechanism for transfer of coherent long-range spin excitation between nanomagnets, showing how Kittel magnons can be used for communication between magnon cavities. Analytical expressions for the magnon transport rate are obtained, and key parameters controlling off-resonant and resonant magnon tunneling regimes are indicated. Physical conditions are determined under which peak values of the rate characterizing the resonant transmission of the Kittel magnon arise either at a fixed tunneling energy with an arbitrary number of units in the ferromagnetic chain or at a fixed number of chain units with a varying tunneling energy. The features of resonant tunneling of the Kittel magnon formed in a magnon cavity at frequencies of about 10 GHz are analyzed. It is also shown that due to the strong photon-magnon coupling in the magnon cavity, at a certain magnetic field, the tunneling flow of magnons can reach an additional peak value, which reflects the process of resonant photon-to-magnon conversion.

An arrayed silicon-based nanotip optical antenna (NOA) architecture for guiding efficient near-infrared imaging detection is proposed. The NOA can be effectively actuated based on the geometric field enhancement due to the tip effect and the patterned redistribution of the surface net charges, leading to a highly localized electron accumulation at the tips, a strong field electron emission away from the tips, and continuously visible cathodoluminescence. The photoelectronic response measurements reveal an effective spectral transformation from the initial infrared region to the visible band with a central wavelength of 544 nm. Spectral characterized analyses exhibit a strong electric-field amplitude gain of 84.77 at 1000 nm and an ultralow radiation transmittance of less than 2% across a broad wavelength range from 400 nm to 14 µm. The measured output electric signal is sensitive to the incident radiation, reaching a high value of 186.05 mV under illumination of 2.47 W. The photoelectric measurements indicate an intense output voltage signal with a nanosecond-level time interval between adjacent output peaks and a shorter duration of a single peak in both the visible and near-infrared regions. The point-spread function of the emitted light beams away from a single nanotip presents a remarkably strengthened and expanded nanofocusing, which means a notable arrayed light-field enhancement in the $\mathrm{Si}$-based NOA configuration. A nanotip-based imaging detector (NID) architecture has been effectively constructed by closely coupling a common complementary metal-oxide semiconductor sensor array with a compact $\mathrm{Si}$-based NOA chip. An obvious improvement in the imaging performance has been realized using the NID construction with a wider radiation response range.

We present a proof-of-concept demonstration of an all-optical inference architecture for classification of handwritten digits using structured Bessel-like beams. By employing a single-plane phase-modulation scheme controlled by only seven trainable parameters, our system steers the beam’s intensity into class-specific regions at the detection plane. These parameters are optimized via gradient descent, enabling direct physical training of the optical platform. In experiments on the MNIST dataset, the system achieves nearly $75\mathrm{\%}$ classification accuracy, underscoring the feasibility of harnessing structured light and minimal hardware complexity for optical machine-learning tasks. This work highlights how the inherent properties of Bessel-like and structured beams can be leveraged to perform classification, offering a pathway toward compact and efficient all-optical computing.

A strongly coupled cavity-quantum-electrodynamics (CQED) system can serve as a powerful platform for quantum optics and quantum information processing; however, the excitation of high-order optical modes can lead to linewidth broadening and diminished mode-matching efficiency, constraining the system’s performance. A degenerate optical cavity, in which all supported modes resonate at the same frequency, provides a means to break through these limitations, facilitating unified interactions between high-order modes and atoms. In this work, we theoretically and experimentally investigate the coupling between high-order optical orbital angular momentum modes and atoms in a degenerate cavity. The cavity consists of a $4f$ system, which possesses a stable self-imaging property that effectively suppresses atom-induced cross-mode coupling. The mode volume of the degenerate cavity and the coupling strength are analytically calculated. The interaction strength between high-order modes and atoms is measured using mode-splitting spectroscopy. The results demonstrate that the collective coupling strength $g\sqrt{N}$ of the atomic ensemble remains independent of the transverse mode distribution. This study establishes a foundation for further exploration of multimode light-matter interactions in CQED systems.

In ultraintense laser experiments, optimizing on-target high-power focal spots to maximize peak intensity is critical for achieving optimal outcomes such as maximized accelerated ion energy. This requires minimizing laser aberrations, which remains challenging due to the lack of in situ, real-time, on-target focal diagnostics at ultrahigh intensity. In this study, we systematically investigated the far-field patterns of a second-order harmonic ($2{\omega }_L$) emitted from thin foil interaction with typical astigmatic laser. Aberrated laser wave fronts and nonuniform intensity profiles jointly shape the accelerated electron sheets together, thereby imprinting astigmatism information in their $2{\omega }_L$ emission far-field patterns. Based on this, we propose an easy-to-implement scheme that utilizes real-time $2{\omega }_L$ far-field-pattern feedback to guide astigmatism compensation via off-axis parabolic mirror (OAP) tuning. Optimized focal spots following this scheme yields higher proton cutoff energy, increased proton number, and more symmetrical beam profiles in laser-driven ion-acceleration experiments.

We propose and experimentally demonstrate an alternative optical method for trapping and cooling dielectric nanospheres at (sub)micron distances from a reflective metallic surface. By translating a tilted mirror towards the focus of a single-beam optical tweezer, the optical trap transitions into an off-axis standing-wave configuration due to interference between the incident and reflected beams. Stable potential minima emerge within a finite overlap region close to the surface, with their number, shape, and distance from the surface tunable via the incidence angle, waist, and polarization of the incoming beam. This configuration enables deterministic selection of trapping sites as the system transitions from the single-beam trap to the off-axis standing-wave trap. We validate this approach using a 170-nm diameter silica sphere in a single-beam trap with a 1.5-$\text{μ}\mathrm{m}$ waist and transitioning it into the second or first potential minimum of the standing-wave trap, located $1.61$ or $0.55\text{μ}\mathrm{m}$ from the surface, respectively. The experimental results align well with our theoretical model, supported by numerical simulations of the Langevin equations of motion. Additionally, we perform optical parametric feedback cooling and electrostatic feedback cooling of all three motional degrees of freedom in a high-vacuum environment. This method provides a robust platform for ultra-sensitive scanning surface force sensing with neutral and charged particles at micron distances from a reflective surface in high vacuum and may open other pathways for short-range gravity or Casimir effect measurements.

The second-harmonic method is an important approach for studying the traditional spin-orbit torques (SOTs). In recent years, research on unconventional SOTs has provided a new approach for zero-field switching of the perpendicular magnetization and thus has received extensive attention. In this work, we theoretically extend the second-harmonic method to include the unconventional SOTs. For the four common magnetic configurations, we have derived the analytical relationship between the second-harmonic Hall (longitudinal) resistance and the (un)conventional SOT coefficients. We have comprehensively taken into account the effects of the anomalous Hall effect, the planar Hall effect, anisotropic magnetoresistance, the spin Hall magnetoresistance effect, the anomalous Nernst effect, the planar Nernst effect, and thermal fluctuations. The fitting results obtained from the numerical simulation verify the correctness of the analytical formula. This work provides a theoretical framework for measuring unconventional SOTs using the second-harmonic method, which is conducive to the development of new all-electrical spintronic devices.

The detection and localization of a source hidden outside the line-of-sight (LOS) traditionally rely on the acquisition of indirect signals, such as those reflected from visible relay surfaces such as floors or walls. These reflected signals are then utilized to reconstruct the obscured scene. In this study, we present an approach that utilizes signals diffracted from an obstacle edge to achieve three-dimensional localization of an acoustic point source situated outside the LOS. The key to the present method is that it removes the dependency on a relay surface for localization. We address two scenarios—a doorway and a convex corner—and propose a localization method for each of them. For the first scenario, we utilize the two edges of the door as virtual detector arrays. For the second scenario, we exploit the spectral signature of a knife-edge diffraction, inspired by the human perception of sound location by the head-related transfer function. In both methods, knife-edge diffraction is utilized to extend the capabilities of non-line-of-sight (NLOS) acoustic sensing, enabling localization in environments where conventional relay-surface based approaches may be limited.