Achieving strongly nonreciprocal scattering in compact linear acoustic devices is a challenging task. One possible solution is the use of time-modulated resonators; however, their implementation in the realm of audible airborne acoustics is typically hindered by the difficulty of obtaining large modulation depth and speeds while managing noise issues. Here, we propose a practical and cost-efficient route to realize simple modulated resonators and observe experimentally the strong nonreciprocal behavior of an acoustic circulator. We propose to modulate the neck cross-section areas of three coupled Helmholtz resonators using rotating circular plates actuated by an electrical motor, and control their phase difference via meshed gears, thereby implementing a modulation scheme with broken time-reversal symmetry that effectively imparts angular momentum to the system. We experimentally demonstrate tunable nonreciprocal behavior with a high nonreciprocal isolation of 34 dB and reflection as low as −9 dB, with insertion losses of 5 dB and parasitic signals below −20 dB. All the experimental results agree well with theoretical and numerical predictions.

External disturbances exciting a mechanical resonator can be exploited to gain information on the environment. Many of these interactions manifest as momentum kicks, such as the recoil of residual gas, radioactive decay, or even hypothetical interactions with dark matter. These disturbances are often rare enough that they can be resolved as singular events rather than cumulated as force noise. While high-$Q$ resonators with low masses are particularly sensitive to such momentum kicks, they will strongly excite the resonator, leading to nonlinear effects that deteriorate sensing performance. Hence, this paper utilizes optimal estimation methods to extract individual momentum kicks from measured stochastic trajectories of a mechanical resonator kept in the linear regime through feedback control. The developed scheme is illustrated and tested experimentally using a prestressed silicon nitride trampoline resonator. Apart from enhancing a wide range of sensing scenarios mentioned above, our results indicate the feasibility of novel single-molecule mass spectrometry approaches.

The hinge and edge states of topological materials have garnered significant attention due to their extraordinary capacity to transmit current against energy loss. In particular, the step edge states (SESs) offer an intriguing avenue for robust and tunable sensing as well as information processing, greatly surpassing existing materials. However, these SESs have not been explored in classical wave systems. Here, we delve into the two-dimensional (2D) system, identifying the resulting step states (SSs) and further elucidating their counterparts as SESs in three-dimensional (3D) acoustic systems. We illustrate two zero-dimensional (0D) SSs within a 2D quadrupole topological insulator, revealing a tendency toward a second-order topology phase as the number of stepped layers increase. The tunable nature of these SSs enables us to manipulate wave transmission by adjusting the geometry of the step boundaries. Furthermore, by simply stacking the 2D models, we successfully achieve the 1D SESs in 3D second-order topological insulators. Our research presents a new pathway for generating 0D localized modes and 1D transmission channels in higher-order topological insulators. The stable SSs and SESs hold potential applications, particularly in wave sensing and trapping.

Low-frequency noise (LFN) is a critical figure of merit for characterizing the performance and application limits of electronic devices and circuits. In two-dimensional (2D) material-based transistors, their higher amplitudes of LFN than those of silicon counterparts are generally attributed to the atomically thin body, which is more susceptible to interfacial scattering. However, with advancing miniaturization of 2D transistors, the quantum capacitance ($C_{\mathrm{q}}$) arising from the confined density of states of the ultrathin channel can impose limitations on electrical performance and inevitably influence the LFN behavior. Herein, to elucidate the fundamental physics of how quantum capacitance impacts LFN, we present a comprehensive study of the LFN characteristics in ${\mathrm{Mo}\mathrm{S}}_2$ field-effect transistors (FETs). It is found that $C_{\mathrm{q}}$ significantly limits transconductance and carrier density, thereby affecting the LFN performance. For monolayer devices, the drain current fluctuations can be explained by the carrier number fluctuation featuring correlated surface mobility fluctuation, and the normalized noise amplitude $(S_{\mathrm{I}}/I_{\mathrm{ds}}^2)$ becomes effectively suppressed in the subthreshold region while enhanced in accumulation because of the influence of $C_{\mathrm{q}}$ on transconductance efficiency. On the other hand, the LFN characteristics inside multilayer transistors follow Hooge’s mobility fluctuation model and are impacted by $C_{\mathrm{q}}$ mainly in strong accumulation. In this regime, $C_{\mathrm{q}}$ leads to an increment of $S_{\mathrm{I}}/I_{\mathrm{ds}}^2$ due to the restrained carrier density in semiconductor channels. Our findings provide unique insight into quantum capacitance effects on LFN characteristics in 2D FETs, and can facilitate their device design, performance optimization, and electronic applications.

We experimentally demonstrate an effective interaction between telecommunication-wavelength optical photons and microwave photons, mediated by Rydberg atoms. A microwave-induced giant cross-Kerr effect is observed in a ${}^{85}\mathrm{Rb}$ vapor cell by our probing higher excited atomic states at the optical telecommunication band, and the measured third-order cross-Kerr coefficient ${\chi }^{(3)}$ can reach approximately $1\times {10}^{-10}{\mathrm{m}}^2/{\mathrm{V}}^2$. These results can be applied to information processing of the integration of wireless and fiber-optic networks in the classical regime or the quantum regime.

With the rapid development of data science, higher performance hardware, such as resistive-switching memory with alternative ultrathin materials, emerges. Although the dielectric constant is an important parameter for photoelectric devices, its tunability in a thin film is needed, a method for its measurement in an ultrathin film is lacking, and its relationship with resistive-switching behavior is rarely investigated. Here, a dielectric-property-tunable thickness-controllable continuous $\mathrm{Co}$-$\mathrm{Ni}$ layered double hydroxide (LDH) film is achieved by bulk-phase doping of polyvinyl alcohol (PVA) using an electrodeposition method, and a general method for dielectric constant measurement of a thin film based on a parallel-plate capacitor is suggested. The $\mathrm{Co}$-$\mathrm{Ni}$ LDH-PVA significantly suppresses dielectric loss by 99%, and an enhanced resistive-switching performance is achieved with an increased initial resistivity, a suppressed leakage current, a reduced set power by 79%, a data retention over ${10}^4$ s, an endurance up to 200 cycles, and a synapselike capability, compared with pure LDH material. The enhanced electrical performance comes from an improved inherent trade-off of dielectric constants inside an electrodeposited LDH film that is tuned by PVA; this is supported by density-functional calculations. This work provides a reference for the selection and modification of resistive-switching materials in relation to dielectric constants.

A key requirement for quantum technologies based on atoms, ions, and molecules is the ability to realize precise phase- and amplitude-controlled quantum operations via coherent laser pulses. However, for generating pulses on the submicrosecond timescale, the characteristics of the optical and electronic components can introduce unwanted distortions that have a detrimental effect on the fidelity of quantum operations. In this paper, we present a compact arbitrary optical waveform modulator that integrates a double-pass acousto-optic modulator for user-specified laser amplitude and phase modulations. Additionally, the module integrates an optical heterodyne detector to extract the precise laser pulse shape in real time. The measured pulse shape is then fed into a digital feedback loop used to estimate the complex-valued transfer function and predistorted input pulses. We demonstrate the performance by generating shaped laser pulses suitable for realizing quantum logic gates with durations down to 180 ns, requiring only a small number of feedback iterations.

The investigation of plane wave to surface wave (or guiding wave) conversion reveals that a highly efficient converter can only be designed as an aperiodic structure. This requirement arises from the momentum mismatch between the plane wave and the surface wave (or guiding wave). Because of this aperiodicity, the design of such highly efficient converters becomes inevitably complex, particularly when the radiation aperture is large, posing a significant challenge to structural engineering. In this work, we propose a straightforward and effective approach for designing a highly efficient converter, which consists of a cascaded metasurface assembled from successively and individually designed subunits. Unlike previous methods, which typically attempt to design the entire structure in a single step, our method designs the structure in two separate steps, thereby significantly reducing design complexity. As a demonstration, a plane-wave-to-guiding-wave metasurface for acoustic waves with 12 units in length is designed. The high efficiency of the structure, operating in a reciprocal state (i.e., functioning as a guiding-wave-to-plane-wave radiator), is validated through both numerical simulations and experimental measurements. This work not only provides a design guideline for a plane-wave-to-guiding-wave converter but also presents a general understanding of the coupling mechanisms between uniform and nonuniform wave fronts.

The emergence of acoustic metamaterials has facilitated the anomalous manipulation of acoustic waves over the past decades. Recently, attention has shifted toward asymmetric acoustic energy transfer. In this study, we design a composite waveguide structure that consists of three waveguide units, which support three odd-symmetric supermodes with dynamically detuned propagation constants. Utilizing the rapid adiabatic passage technique, we numerically and experimentally demonstrate three distinct adiabatic transfers of acoustic energies in the designed composite waveguide structures. For the absence of crossing points in the detuned supermode propagation constants, a complete recovery of the acoustic energy is achieved in the excited waveguide unit. When three detuned supermode propagation constants are configured with either one or two crossing points throughout the entire adiabatic process, the composite waveguide structure can be used to selectively realize the symmetric transfer or asymmetric cyclic transfer of the acoustic energy among the three waveguide units. Furthermore, the asymmetric cyclic transfer of the acoustic energy renders the broadband and robust characteristics. Our findings offer promising applications in the design of acoustic circulators and underwater communication systems.

Metal-organic frameworks (MOFs) have been regarded as promising candidates for gas fuel storage. It is known that a large amount of heat will be released (exothermic) or adsorbed (endothermic) during the gas storage process, which leads to a large temperature change in the system and, in turn, affects the usable gas uptake capacity. It is therefore necessary to investigate thermal transport in gas-adsorbed MOFs. By using atomistic simulations, we here systematically study the thermal transport in ${\mathrm{CH}}_4$-, ${\mathrm{C}}_2{\mathrm{H}}_6$-, and ${\mathrm{H}}_2$-adsorbed MOF-199, which usually refers to HKUST-1. We find that the room temperature thermal conductivity of ${\mathrm{CH}}_4$- and ${\mathrm{C}}_2{\mathrm{H}}_6$-adsorbed systems first decreases greatly to approximately 40% of the original value and then converges with the amount of adsorbed gas molecules. However, for ${\mathrm{H}}_2$-adsorbed systems at room temperature, the corresponding thermal conductivity decreases from approximately 1.37 W/mK to approximately 0.69 W/mK and then increases to approximately 1.16 W/mK with increase of the amount of adsorbed ${\mathrm{H}}_2$ molecules. It is further shown that the thermal conductivity contributed by the HKUST-1 framework decreases monotonously with increase of the amount of adsorbed gas molecules owing to the increased scattering between the HKUST-1 framework and adsorbed gas molecules. The thermal energy transferred by the adsorbed ${\mathrm{CH}}_4$ and ${\mathrm{C}}_2{\mathrm{H}}_6$ (${\mathrm{H}}_2$) molecules increases a little (greatly) with increase of the amount of adsorbed gas molecules. This is because the adsorbed ${\mathrm{H}}_2$ molecules can diffuse farther in HKUST-1 than the adsorbed ${\mathrm{CH}}_4$ and ${\mathrm{C}}_2{\mathrm{H}}_6$ molecules, which is caused by the small size of ${\mathrm{H}}_2$ molecules and weak interactions between the HKUST-1 framework and ${\mathrm{H}}_2$ molecules. Therefore, the adsorbed ${\mathrm{H}}_2$ molecules can effectively transfer thermal energy through both conductive and diffusive pathways, and the thermal conductivity of the saturated-${\mathrm{H}}_2$ system is much higher than that of the saturated-${\mathrm{CH}}_4$ and saturated-${\mathrm{C}}_2{\mathrm{H}}_6$ systems. Our results provide a physical picture of thermal transport in gas-adsorbed MOFs, which should facilitate the design of high-performance MOF-based gas storage systems.

We model a periodic thin-film superconducting system containing two differently shaped antidots: circular and equilateral-triangular. In the absence of an external field, the system displays two stable states as a function of the applied current: (i) a vortex-free state at low current and, (ii) above some critical current, a state involving both a vortex and an antivortex pinned to the two respective pinning sites. At still higher currents, the system becomes unstable to repeated nucleation and annihilation of moving vortex-antivortex pairs. The two states have distinct inductive responses. It is noted that these properties open the possibility for these systems to be used as cryogenic circuit or memory elements.

Privacy amplification (PA) is a vital step in the postprocessing stage of quantum key distribution, which can extract a secure key from a source partially leaked to the environment. We propose a PA scheme that uses the square hash (SQH)–modular arithmetic hash (MH) function. In consideration of a potential quantum attacker, we use the trace distance as a metric to measure the closeness between two classical-quantum states. We transform a raw key state to a processed state using this scheme and derive the trace distance between the processed state and the ideal target state. It is proven that the trace distance can be reached as small as desired. Additionally, our approach accelerates the SQH-MH function through the number-theoretic transform, reducing the computational complexity to $O(n\log n)$. On the basis of a CPU, a maximum throughput rate of 1.06 Gbit/s is achieved, and the results show that our algorithm demonstrates good stability of the throughput rate when handling tasks with different compression ratios.

Topological insulator spin-momentum locked surface states have been of interest for their contribution to highly efficient charge-to-spin conversion. However, the potential interactions between spin states in topological insulators and orbital momentum from light metals remain unexplored. Here, leveraging orbital and spin torques in the ferromagnet/$\mathrm{Cu}/{\mathrm{Bi}}_{0.85}{\mathrm{Sb}}_{0.15}$ heterostructure, a significant enhancement in dampinglike spin efficiency of up to six times is observed. We establish that the underlying mechanism for the improvement is due to the enhanced crystallinity of the topological insulator when $\mathrm{Cu}$ is used as an interlayer, coupled with substantial bulk orbital momentum generated by the light metal $\mathrm{Cu}$. This complementary combination of topological insulators and light metals exceeds their individual contributions, laying critical groundwork for effective performance.

Quantum information processing faces a significant hurdle: noise. Different noise sources induce varying errors in quantum operations depending on the underlying dynamics. To gain a deeper understanding of these error mechanisms, we introduce the concept of quantum error evolution diagrams (QEEDs). QEEDs establish a dual correspondence between driven noisy quantum dynamics and geometric space curves, providing quantitative geometric metrics to assess the severity of the noises. This framework enables the design of universal robust quantum gates that correct errors induced by generic noise. Additionally, we present a protocol for constructing a universal set of single- and two-qubit robust quantum gates with simple and smooth control pulses of arbitrary length and fidelities exceeding 99.99% across a wide range of noise strengths. Our work provides new insights into the geometric nature of noisy quantum dynamics and paves the way for developing strategies to dynamically correct quantum errors.

Imaging spin-wave propagation in magnetic materials in a wide frequency range is crucial for understanding and applying spin-wave dynamics. Recently, nitrogen-vacancy (N-V) centers in diamond have attracted attention as sensors capable of quantitatively measuring the amplitude and phase of coherent spin waves. However, the conventional sensing protocol has been limited to detecting spin waves whose frequencies match the resonance frequency of the N-V spins. We demonstrate that by utilizing the ac Zeeman effect, it is possible to image spin waves propagating in an yttrium iron garnet thin film over a wide frequency range up to a maximum detuning of $567\mathrm{M}\mathrm{Hz}$ without changing the external magnetic field. Our results expand the applicability of N-V centers for spin-wave sensing and pave the way for quantitative investigations of the dynamics in various magnetic materials, such as metallic ferromagnets and van der Waals magnets.

For magnetic-resistant and ultrafast transverse thermoelectric converters, antiferromagnets with a collinear Néel vector have unique advantages but their anomalous Nernst effect (ANE), as the fundamental requirement, remains unachieved due to the spin-degenerated bands. Here, we realize the nonvolatile ANE in an altermagnet from ${\mathrm{Mn}}_5{\mathrm{Si}}_3$ thin films with a collinear Néel vector under strain, where the Berry curvature from the intersections of spin-splitting bands (instead of a tiny net moment) determines the anomalous Nernst conductivity. The ANE undergoes a sixfold enhancement via doping, most likely due to the raised Fermi level. Order parameter fluctuations induce unique temperature dependence, which also applies to other suitable altermagnets. Our work not only fills a longstanding gap by observing the nonvolatile ANE in material with a collinear Néel vector but also enlightens thermoelectric physics related to spin-splitting bands.

Recent experimental studies demonstrated the non-Hermitian skin effect in an electric circuit network made of lumped elements that usually work work below megahertz frequencies. To realize the non-Hermitian skin effect at gigahertz frequencies, we design a distributed-element circuit network by using microwave transmission lines. The circuit proposed in this work can easily embed a ferromagnetic magnon mode in it. By further considering magnon-photon coupling, one can achieve the non-Hermitian skin effect of a hybridized quasiparticle, i.e., a cavity magnon polariton. As the driving frequency increases, the eigenstates of dissipative magnon-photon coupling are first localized at the left boundary and then at the right boundary, forming a single left-right transition. However, for the coherent coupling, multiple left-right-left-right transitions occur. The results given in this work open up promising roads for the design of distributed-element microwave circuits and exploration of the non-Hermitian physics in a polariton.

Fluxonium qubits are recognized for their high coherence times and high operation fidelities. These are attributed to their unique design incorporating a superinductor, which is typically implemented using an array of over 100 Josephson junctions; however, this complexity poses significant fabrication challenges, particularly in achieving high yield and junction uniformity with traditional methods. Here, we introduce an overlap process for Josephson-junction fabrication that achieves nearly 100% yield and maintains uniformity across a 2-inch (50.8-mm) wafer with less than 5% variation for the phase-slip junction and less than 2% for the entire junction array. We use a compact junction array design that achieves state-of-the-art dielectric loss tangents and flux noise levels, as confirmed by multiple devices. This enables fluxonium qubits to reach energy relaxation times exceeding 1 ms at the flux-frustration point. This work paves the way for scalable, high-coherence fluxonium processors using processes compatible with complementary metal-oxide semiconductor manufacturing, marking a significant step toward practical quantum computing.