Acoustic droplet ejection (ADE) technology has gained significant attention in synthetic biology and drug discovery due to its noncontact dispensing, low contamination risk, and high-accuracy droplet handling capabilities. However, current focused-field-based ADE technologies are limited in throughput compared to traditional pipetting workstations. To address this limitation, we propose an artificial-structure-based holographic acoustic field with multiple focal spots, enabling the parallel ejection of multiple droplets with nanoliter-scale volumes, thereby enhancing throughput. By utilizing computer-generated holography, we can generate focal spots at desired positions, facilitating on-demand droplet ejection patterns. Given the common use of multiwell plates in liquid handling, we present a modified iterative angular spectrum approach to design the holographic acoustic fields, achieving precise and parallel droplet ejection from distinct wells of a multiwell plate. Our research introduces an innovative ADE system for parallel liquid sample transfer, providing a noncontact, straightforward, and cost-effective strategy for high-throughput and on-demand ADE-based liquid transfer technology.

Addressing combinatorial optimization problems (COPs) using conventional computational approaches is often resource intensive in terms of time and power consumption. The oscillator-based Ising machine, which combines oscillator units with the Ising model, presents a promising avenue for efficiently solving COPs. In this context, we explore the viability of leveraging self-sustained magnetic oscillations, specifically the spin Hall nano-oscillator (SHNO), to establish an electrically coupled oscillator Ising machine. To evaluate the potential applications of such Ising machines, we theoretically construct networks of SHNOs and deploy them to address two prevalent COPs: the max-cut problem and the traveling salesman problem (TSP). For the max-cut problem, we propose an optimized annealing schedule that can significantly enhance the success probability of finding the optimal solution. In the case of the TSP, we showcase the capability of the SHNO-based Ising machine to address this problem by introducing a Zeeman coupling term to account for penalty considerations, along with a suitable normalization strategy to effectively incorporate distance-related issues inherent in the TSP. Our study offers comprehensive investigations into the coupled SHNO networks, providing insights for the design and the development of unconventional computing architectures based on SHNOs for quantum-inspired applications.

We have fabricated a doubly clamped microelectromechanical system (MEMS) beam resonator and investigated the bending-bending and bending-torsional internal mode-coupling (MC) effects, which can be separately excited by choosing the driving phase of the phase-locked loop. We have found that the linewidths of the coupled modes become much sharper owing to the frequency stabilization effect in the MC condition. Furthermore, when the MEMS resonator is driven in the bending-bending MC condition, strong coherent amplitude exchange between the first bending mode (4%) and the third bending mode (17%) is observed, indicating a very strong MC effect. In contrast, such a coherent amplitude exchange is not clearly visible for the coupling between the first bending mode and the first torsional mode. The result suggests that the bending-bending MC is much stronger than the bending-torsional MC, probably because of the similarity in the mode shape for the bending-bending MC. In addition, we found that the thermal responsivity of the MEMS resonator is dramatically enhanced when an external heat modulated at the amplitude exchange frequency is applied to the beam. We provide a mathematical model that explains the observed MC effects and damping behaviors. The theory shows an excellent agreement with the experimental results.

A controlled noise environment provides a unique platform for the investigation of various quantum technologies. Here, we demonstrate a technique to engineer arbitrary unitary baths in quantum systems with solid-state spin systems. A wide variety of classical noise models, including the generation of dephasing noise and amplitude-damping noise was realized through precise modulation of microwave signals. By measuring the power spectral density of the noise with the aid of single nitrogen-vacancy (N-$V$) color centers in diamond, we confirm that the generated noise closely matches the theoretical expectations. This technique serves as a powerful toolkit for validating quantum control protocols, simulating decoherence processes in other quantum systems, and generating baths essential for studying quantum thermodynamics.

The simplified scaling of the orbital upper critical field, $H_{c2}(T)$, for an isotropic $s$-wave superconductor is introduced. To facilitate the analysis of the experimental data, we suggest a simple but accurate approximation of the Helfand-Werthamer upper critical field in the entire temperature range valid for any transport scattering rate: $H_{c2}/H_{c2}(0)\approx (1-t^2)/(1+0.42t^{1.47})$.

Because of their long mean free path and superior current-carrying capabilities, carbon nanotubes (CNTs) are considered as an alternative for $\mathrm{Cu}$ in future interconnects. To simulate their dynamical properties, a linear equivalent-circuit model is usually invoked containing, among other things, a kinetic inductance and a quantum capacitance. As this equivalent circuit has been derived for perfect CNTs, the effect of imperfections is lacking. Still, imperfections considerably change the CNTs’ characteristics, necessitating the development of novel accurate simulation techniques to aid the electronic interconnect designer. Therefore, in this paper, an ac nonequilibrium Green’s function modeling technique is constructed for CNT interconnects, yielding a fully quantum mechanical first-principles method. The implemented method abandons the often-used small-signal requirement and includes the self-consistent solution with the Poisson equation. Additionally, a new, generally valid approach to partition a CNT into small units is presented. This allows us to rewrite the Hamiltonian into a block tridiagonal form with small submatrices and, subsequently, to employ the recursive Green’s function algorithm in an efficient way. Comparison with the equivalent-circuit model serves as validation of the constructed technique, which is an essential, but challenging, task for periodically driven quantum transport problems. The results show that, in order to accurately model the kinetic inductance, the self-consistent solution with the Poisson equation is a fundamental requirement. The constructed method is used to investigate finite-size effects and vacancies, from which it is argued that local defects can, in the linear equivalent-circuit model, be approximated by means of an additional series resistance as long as the applied bias is small. For a large bias, however, nonlinear effects come into play and the circuit model is no longer valid. Lastly, it is demonstrated, both analytically and numerically, that the even harmonics of the current and the potential are absent within the nearest-neighbor tight-binding approximation for the Hamiltonian of the CNTs.

We investigate the presence of topological gaps in a twist-modulated quasiperiodic, locally resonant metastructure. This work considers an elastic plate featuring a square lattice of resonators modulated by a twisted potential, which renders the formation of moiré superlattices within a single resonant layer. This setup provides a platform to explore the topological properties of the emerging 2D quasiperiodic patterns. Our theoretical simulations reveal a fractal-like spectrum dependent on the twist angle and bandgaps characterized by nonzero topological invariants reminiscent of the 4D quantum Hall effect. The model is then physically implemented in a ${\mathrm{LEGO}}^{\text{®}}$ metastructure with reconfigurable resonators whose heights can be independently adjusted according to the twist angle. The experimentally observed bandgaps and fractal-like spectrum are supported by finite element simulations, confirming the appearance of topological gaps in the 2D quasiperiodic lattices. This twist-induced quasiperiodic metastructure serves as a convenient platform to explore diverse topological phenomena inspired by twistronics and quasiperiodic patterning without multilayered fabrication requirements.

The integration of memristor-based devices in large-scale passive arrays necessitates the development of self-rectifying memristors (SRMs). However, existing SRMs face significant challenges in achieving high on:off and self-rectification ratios while maintaining complementary metal-oxide semiconductor (CMOS) compatibility. Here, we present a SRM with a $\mathrm{Pt}/{\mathrm{WO}}_3/{\mathrm{WO}}_{3-x}/\mathrm{Ti}\mathrm{N}$ structure, which exhibits an impressive rectification ratio (approximately ${10}^5$), satisfactory on:off ratio (around ${10}^3$), low operation voltage (2 V), and high stability (>${10}^6$ s, ${10}^4$ cycles). When incorporated into a 100 × 100 array, this device achieves a remarkable resistance reading accuracy of 97.3%. Furthermore, by setting the read margin to 10%, the passive array integrated with this device can reach a storage capacity of up to 180.3 Gb. At the same time, we simulate an on-chip convolutional neural network based on a 32 × 32 passive array, achieving a recognition accuracy of 99.1% for the handwritten digits “0,” “1,” and “2.” The use of CMOS-compatible materials and a simple single-oxide-layer structure can significantly reduce industrial costs. These advancements offer valuable insights for the development of practical and scalable SRMs, paving the way for their widespread integration in large-scale in-memory computing applications.

We introduce a quantum-inspired algorithm for graph coloring problems (GCPs) that utilizes qudits in a product state, with each qudit representing a node in the graph and parameterized by $d$-dimensional spherical coordinates. We propose and benchmark two optimization strategies: qudit gradient descent, initiating qudits in random states and employing gradient descent to minimize a cost function; and qudit local quantum annealing, which adapts the local quantum annealing method to optimize an adiabatic transition from a tractable initial function to a problem-specific cost function. Our approaches are benchmarked against established solutions for standard GCPs, showing that our methods not only rival but frequently surpass the performance of recent state-of-the-art algorithms in terms of solution quality and computational efficiency. The adaptability of our algorithm and its high-quality solutions, achieved with minimal computational resources, point to an advancement in the field of quantum-inspired optimization, with potential applications extending to a broad spectrum of optimization problems.

We theoretically propose how to achieve nonreciprocal enhancement of bipartite and tripartite entanglement using an optomechanical resonator coupled to a nonlinear optical resonator. We find that by our pumping the nonlinear resonator, directional optical squeezing can occur along the pump direction, resulting in an asymmetric detuning and chiral photon interaction between the two resonators. As a result, nonreciprocal enhancement of bipartite and tripartite entanglement can be achieved, exhibiting robustness regarding bath temperature. Specifically, in one direction, bipartite entanglement can be enhanced by about 2 times and tripartite entanglement can be enhanced by about 3.5 times compared with the opposite direction. Our work provides a route to manipulate and enhance nonreciprocal bipartite and tripartite entanglement using directional quantum squeezing, which may find potential applications in constructing chiral quantum networks.

Local local oscillator (LLO) continuous-variable quantum key distribution (CVQKD) systems have gained prominence due to their security advantages with LO generated locally. However, the nonsynchronization of two lasers leads to phase drift, a detrimental phenomenon that restricts excess noise suppression. Prevailing solutions, such as pilot-multiplexing schemes, offer better recovery results than pilot-sequential schemes, but at the expense of increased system complexity and demanding technical requirements. In this work, we introduce an innovative carrier-recovery strategy employing the long-short-term memory (LSTM) neural network, aiming to optimize the recovery performance in the simple self-referenced CVQKD systems with the pilot-sequential scheme. Through temporal modeling, the LSTM network proficiently predicts and compensates for the rapid phase drifts. Experimental validations conducted in both fiber and free-space channels underscore the effectiveness of our method for carrier recovery. In practical CVQKD experiments, our LSTM-based approach yields a near 50% reduction in excess noise, leading to a significant increase in secret key rates when compared with the traditional pilot-sequential method. The simplicity of hardware and operation positions our scheme as a superior alternative for current mainstream pilot-multiplexing CVQKD systems, particularly appealing for on-chip implementation and satellite-to-ground quantum communication applications.

We show theoretically that photophoretic aircraft would greatly benefit from a three-dimensional hollow geometry that pumps ambient air through sidewalls to create a high-speed jet. To identify optimal geometries, we developed a theoretical expression for the lift force based on both Stokes (low Reynolds number) and momentum (high Reynolds number) theory and validated it using finite-element fluid-dynamics simulations. We then systematically varied geometric parameters, including Knudsen pump porosity, to minimize the operating altitude or maximize the payload. Assuming that large vehicles can be made from nanocardboard material, as previously demonstrated at smaller scales, the minimum altitude such vehicles can levitate at is approximately 55 km, while the payload can reach approximately 1 kg at an altitude of 80 km for vehicles with a 10 m diameter. In all cases, the maximum areal density of the sidewalls cannot exceed a few grams per square meter, demonstrating the need for ultralight porous materials.

Here, we investigate the effective response of three-dimensional spacetime crystals formed by spherical scatterers under a traveling-wave modulation. We develop an analytical formalism to homogenize the spacetime crystals that extends the renowned Clausius-Mossotti formula to time-varying platforms. Our formalism shows that traveling-wave spacetime crystals can be used to engineer a wide range of classes of nonreciprocal bianisotropic couplings in the long-wavelength limit. In particular, our theory reveals the possibility of realizing a purely isotropic Tellegen response in crystals formed by interlaced sublattices of scatterers subjected to different modulation velocities. Furthermore, we introduce a class of generalized Minkowskian crystals that display invariance under arbitrary Lorentz boosts aligned with a fixed spatial direction. We prove that such systems are formed by pseudouniaxial materials with the principal axis aligned parallel to the modulation velocity. The electromagnetic response of such generalized Minkowskian crystals is indistinguishable from that of moving photonic crystals.

Multiband topology, as a unique feature of topological phenomena in classical wave systems, has attracted much attention owing to its potential applications in broadband topological devices. Here we study the multiband topology in a coupled two-chain Su-Schrieffer-Heeger model where the two Su-Schrieffer-Heeger chains with different hopping configurations are coupled via interchain hopping. We find that the topological transitions of different band gaps can be triggered by our tuning the interchain and intrachain hoppings, leading to a rich phase diagram with various multiband topological effects. Using acoustic metamaterials and pump-probe measurements, we confirm in experiments these multiband topological effects by observing the emergence and disappearance of the topological edge states in different band gaps, which are in excellent agreement with the theory. The findings here provide a promising way toward multiband topology with clean physics and richness, which can serve as a prototype case for understanding multiband topology.

Nonlinear transport plays a vital role in probing the quantum geometry of Bloch electrons, valley chirality, and carrier scattering mechanisms. The nonlinear Hall effect, characterized by a nonlinear scaling of Hall voltage with longitudinal current, has been explored to reveal the Berry curvature and quantum metric–related physics. In this work, we extend the study of nonlinear transport to spin and valley degrees of freedom. Using bilayer graphene devices with ${\mathrm{Fe}}_3{\mathrm{Ge}\mathrm{Te}}_2$ contacts, we observe a second-order nonlinear spin current exhibiting spin-valve-like behavior. By tracking magnetic moment precession under an in-plane magnetic field, we identify a significantly enhanced critical magnetic field required for in-plane rotation, suggesting out-of-plane valley polarization induced by ferromagnetic proximity. These findings offer deep insights into the interplay of valley and spin in second-order nonlinear transport, opening avenues for promising device applications.

Notwithstanding its relevance to many applications in sensing, security, and communications, electrical generation of narrow-band midinfrared light remains highly challenging. Unlike in the ultraviolet or visible spectral regions, few materials possess direct electronic transitions in the midinfrared and most that do are created through complex band-engineering schemes. An alternative mechanism, independent of dipole-active material transitions, relies instead on energy lost to the polar lattice through the Coulomb interaction. Longitudinal phonons radiated in this way can be spectrally tuned through the engineering of polar nanostructures and coupled to localized optical modes in the material, allowing them to radiate midinfrared photons into the far field. A recent theoretical work has explored this process, providing for the first time an indication of its technological relevance when compared to standard thermal emitters. In order to do so, it has nevertheless used an equilibrium model of the electron gas, making the use of this model difficult to inform the design of an optimal device to experimentally observe the effect. The present paper removes this limitation, describing the electron gas using a rigorous self-consistent nonequilibrium Green’s function model, accounting for variations in material properties across the device and electron-electron interactions. Although the instability of the Schrödinger-Poisson iteration limits our studies to the low-bias regime, our results demonstrate emission rates comparable to that of room-temperature thermal emission despite such low biases. These results provide a pathway to the design of a confirmatory experiment of this new emission channel, which could power a new generation of midinfrared optoelectronic devices.

Exploring the power and phase profiles of spin waves not only enhances our fundamental understanding of magnetic materials but also opens up avenues for energy-efficient technologies such as spintronics, magnonics, and potentially reservoir computing. Here, we present the power-phase distributions and their tunability of a surface-acoustic-wave-driven “magnon microwave antenna” (MMA), comprising patterned arrays of magnetostrictive nanomagnets embedded in piezoelectric heterostructures. The MMA generates tunable microwave frequencies without external bias fields, thanks to phonon-magnon coupling, producing multimode microwave frequencies with nonvolatile spin textures. A comprehensive static magnetic study elucidates the crucial role of the demagnetization energy distribution, rather than its overall magnitude in magnetization reversal processes. Additionally, functional tunability could be achieved through amplitude-dependent training using various combinations of nanowire and nanodot dimensions, topologies, material properties, and array configurations. The nonvolatile nature of the spin textures generated in the MMA under bias-field-free conditions is promising for energy-efficient logic and low-power computing applications. Thus this work introduces a novel alternative approach, paving the way to utilize these MMAs for on-chip reservoir computing, where amplitude varies at the operating frequency.

We demonstrate an efficient switchable spintronic terahertz emission from a Co(2 nm)/Pt(2 nm) bilayer split into a grating of microstripes or nanostripes in applied external magnetic field of the order of 10 mT. The terahertz signal is effectively emitted if the samples are magnetized perpendicular to the stripes direction and decreases upon a ${90}^{\circ }$ rotation of a sample. The maximal 27-fold ratio of amplitude change is achieved for the sample with a $2\text{μ}\mathrm{m}$ width of stripes. For the samples with easy magnetization axis directed perpendicular to stripes the terahertz signal is linearly polarized in the direction of the stripes and abruptly switches during the sample remagnetization process. If the easy axis is along the stripes, the terahertz source is almost switched off in a zero magnetic field.

Current quantum computers suffer from noise that stems from interactions between the quantum system that constitutes the quantum device and its environment. These interactions can be suppressed through dynamical decoupling to reduce computational errors. However, the performance of dynamical decoupling depends on the type of system-environment interactions that are present, which often lack an accurate model in quantum devices. We show that the performance of dynamical decoupling can be improved by optimizing its rotational gates to tailor them to the quantum hardware. We find that, compared to canonical decoupling sequences, such as CPMG, XY4, and UR6, the optimized dynamical decoupling sequences yield the best performance in suppressing noise in superconducting qubits. Our work thus enhances existing error suppression methods, which helps increase the circuit depth and result quality on noisy hardware.