Phase transitions of condensed matter have long been a spotlight issue studied by extensive theoretical and experimental investigations. Machine learning can build an integral model-dominant workflow to statistically analyze the collective dynamics of materials and deduce the structure. We use a support-vector-machine algorithm to propose an effective method to recognize the orthorhombic, tetragonal, and cubic phases as well as to construct the phase diagram in ferroelectric crystals by mining and learning the behavioral vectors of the phonon vibrations in a crystalline lattice from Raman scattering, which is a tool typically used to detect structural properties at the molecular level. This study creates a unifying framework including material synthesis and characterization, feature engineering and principal-component analysis, learner evaluation and optimization, structure prediction, and future development of the model. It paves the way to the application of a generic approach for predicting unexplored structures and materials in the future.

Asymmetric wave manipulation has attracted growing interest due to its great importance in practical applications. We design and demonstrate a planar acoustic metamirror for realizing asymmetric sound absorption with a controllable retroreflection coefficient, which is absent in conventional lossless metasurfaces. We design the metamirror by realizing the required theoretical surface impedance profile, and then numerically and experimentally demonstrate its asymmetric response. The measured and simulated acoustic fields agree well with each other, which shows that the proposed metamirror can yield strongly asymmetric sound absorption: retroreflection and nearly full absorption for two opposite incident angles. In addition, the measured retroreflection coefficient and retroreflection angle are very close to the design values. We find that the asymmetrical excitation of evanescent waves plays a key role in the realization of asymmetric absorption. The proposed metamirror enriches the functionalities for acoustic wave manipulation and has prospective applications in many fields, such as acoustic antennas, acoustic sensing, and angle-encoded steganography.

Graph states and hypergraph states are of wide interest in quantum information processing and foundational studies. Efficient verification of these states is a key to various applications. Here we propose a simple method for verifying hypergraph states, which requires only two distinct Pauli measurements for each party, yet its efficiency is comparable to the best strategy based on entangling measurements. For a given state, the overhead is bounded by the chromatic number and degree of the underlying hypergraph. Our protocol is dramatically more efficient than all previous protocols based on local measurements, including tomography and direct-fidelity estimation. It enables the verification of hypergraph states and genuine multipartite entanglement of thousands of qubits. The protocol can also be generalized to the adversarial scenario, while achieving almost the same efficiency. This merit is particularly appealing to demonstrating blind measurement-based quantum computation and quantum supremacy.

We introduce a conceptual design of a free-space thin-sheet isolator with an unlimited aperture and the possibility of a broadband omnidirectional rejection of the backward-propagating light. The proposed design involves a multilayered resonant cavity incorporating subwavelength magnetic layers, dichroic nanolayers, and an optional metallic nanolayer. The cavity resonance enhances the Faraday rotation produced by the subwavelength magnetic layers, while providing nearly total absorption of the backward-propagating light by the dichroic nanolayers. The latter is a necessary and the most challenging condition for a thin-sheet isolator with an unlimited aperture to function. The (optional) metallic nanolayer provides rejection of the obliquely incident light, which otherwise would be partially transmitted in either direction. Our numerical simulations and quasioptical measurements at millimeter-wave frequencies illustrate how the key elements of the layered-sheet isolator work. Our approach can be scaled down to long- and midinfrared wavelengths.

This Paper introduces analyzing and modeling dual silicon-oxy-nitride [${\mathrm{Si}\mathrm{O}}_x{\mathrm{N}}_y$] racetrack resonators (RRs) for biosensing applications. The geometric configuration of the resonators and design of alternative small sensing windows result in the realization of optical biosensors with a highly improved intrinsic limit of detection (ILOD). A small sensing window, located above the coupling region of dual RRs, can be used to maximize the total quality factor (minimized ILOD). The best characteristics for each optical component in the parallel-coupled RR-based biosensors are single-mode-channel waveguides with dimensions of $35\times 1\mu {\mathrm{m}}^2$; the radius of curvature $90\mu \mathrm{m}$ and quality factors up to approximately $5.53\times {10}^6$ for RRs. The biosensing performance of our proposed configuration is compared with other experimental and simulated biosensor devices. Our structure shows an ILOD of approximately $1.81\times {10}^{-6}$ refractive index units (r.i.u.), which significantly improved 100 times compared with the traditional single ${\mathrm{Si}\mathrm{O}}_x{\mathrm{N}}_y$ RR biosensor. This ultra-improved ILOD parameter is found in the dynamic refractive index range of 1.332–1.350 r.i.u. It shows that the proposed biosensor could be a promising diagnostic candidate for analyzing different components of blood samples, which is especially important in the early detection of some critical diseases such as prostate cancer.

High-quality epitaxial ferrites, such as low-damping $\mathrm{Mg}\mathrm{Al}$-ferrite (MAFO), are promising nanoscale building blocks for all-oxide heterostructures driven by pure spin current. However, the impact of oxide interfaces on spin dynamics in such heterostructures remains an open question. Here, we investigate the spin dynamics and chemical and magnetic depth profiles of 15-nm-thick MAFO coherently interfaced with an isostructural 1–8-nm-thick overlayer of paramagnetic ${\mathrm{Co}\mathrm{Cr}}_2{\mathrm{O}}_4$ (CCO) as an all-oxide model system. Compared to MAFO without an overlayer, effective Gilbert damping in MAFO/CCO is enhanced by a factor of $>3$, irrespective of the CCO overlayer thickness. We attribute this damping enhancement to spin scattering at the approximately 1-nm-thick chemically disordered layer at the MAFO-CCO interface, rather than spin pumping or proximity-induced magnetism. Our results indicate that damping in ferrite-based heterostructures is strongly influenced by interfacial chemical disorder, even if the thickness of the disordered layer is a small fraction of the ferrite thickness.

We experimentally demonstrate the ability of a nonlinear self-channeling beam to resist turbulence-induced spreading and scintillation. Spatio-temporal data is presented for an 850-m long, controlled turbulence range that can generate weak to strong turbulence on demand. At this range, the effects of atmospheric losses and dispersion are significant. Simulation results are also presented and show good agreement with experiment.

The simple quantum setup of a Fabry-Perot interferometer is found to exhibit very high directional preference to impinging particle beams, with use of realistic media. Numerous optimized designs, acting as extremely sharp angular filters of matter waves, are determined by trying and testing every single combination of actual materials picked from a long list. Two types of resonances are identified whose different mechanisms are demonstrated through the spatial distribution of wave-function magnitude and probability current, while their robustness with respect to fabrication defects is also examined. Such findings offer additional degrees of freedom when designing architectures for a broad range of quantum-engineering applications that involve beam tunneling and provide a set of limits for the angular selectivity that can be achieved with the considered geometry.

One long-term goal of phononic communications is to achieve the controlled transport of elastic wave signals with enhanced information capacity and improved robustness, which is still challenging given the complexity of elastic waves in terms of vectorial movement and multiple polarizations. Here, we present our theoretical and experimental study of the robust transport of elastic wave signals along interfaces between distinct topological phases. These topological edge states are robust against defects and disorders because they are jointly protected by both pseudospin and valley degrees of freedom (DOFs); thus naturally providing doubled information carriers within a single channel. A topology-based beam splitter is experimentally demonstrated, where the signal's propagation path is uniquely determined and topologically protected. Edge states between distinct topological phases not only offer a route towards new topological phenomena, but also open up an avenue for the design of high-capacity and robust phononic communication devices through discrete DOF multiplexing.

While wired-power-transfer devices ensure robust power delivery even if the receiver position or load impedance changes, achieving the robustness of wireless power transfer (WPT) is challenging. Conventional solutions are based on additional control circuits for dynamic tuning. Here we propose a robust WPT system in which no additional tuning circuitry is required for robust operation. This is achieved by our systematically designing the load and the coupling link to be parts of the feedback circuit. Therefore, the WPT operation is automatically adjusted to the optimal working condition under a wide range of load and receiver positions. In addition, pulsed oscillations instead of single-harmonic oscillation are adopted to increase the overall efficiency. An example system is designed with use of a capacitive coupling link. It realizes a virtual, nearly-ideal oscillating voltage source at the load site, giving efficient power transfer comparable to that of the ideal wired-connection scenario. We numerically and experimentally verify the robustness of the WPT system under the variations of load and coupling, where coupling is changing by our varying the alignment of aluminum plates. The working frequency and the transferred power agree well with analytical models. The proposed paradigm can have a significant impact on future high-performance WPT devices. The designed system can also work as a smart table supporting multiple receivers with robust and efficient operation.

Coupling-enabled frequency synchronization is essential for an array of light sources operating in a photonic system. Using a two-dimensional nonlinear oscillator model of a laser, we analyze the role of two distinct types of coupling, dispersive and dissipative, in promoting frequency locking between two nonidentical lasers. In both scenarios the two oscillators synchronize into a frequency-locked state when the coupling level exceeds a critical value. We show that the onset of dispersive and dissipative synchronization processes is associated with hard and soft frequency transitions, respectively. Through analysis and numerics, we demonstrate that the dispersive coupling yields bistable synchronization modes, accompanied by asymmetric intensities, and the frequency controlled by the coupling strength. In contrast, dissipative coupling induces monostable synchronization with symmetric intensities and a coupling-independent frequency. Our results are expected to provide a basis for understanding the coupling mechanisms of frequency locking toward controlling synchronization in laser arrays.

We investigate, both theoretically and experimentally, the drift, diffusion, and recombination of excitons in the strain field of an edge threading dislocation intersecting the $\mathrm{Ga}\mathrm{N}${0001} surface. We calculate and measure hyperspectral cathodoluminescence maps around the dislocation outcrop for temperatures between 10 and 200 K. Contrary to common belief, the cathodoluminescence intensity contrast is only weakly affected by exciton diffusion but is caused primarily by exciton dissociation in the piezoelectric field at the dislocation outcrop. Hence, the extension of the dark spots around dislocations in the luminescence maps cannot be used to determine the exciton diffusion length. However, the cathodoluminescence energy contrast, which reflects the local band-gap variation in the dislocation strain field, does sensitively depend on the exciton diffusion length and hence enables its experimental determination.

Radiant energy-flow control and privacy control are two important features for smart windows (or glass). Current smart window technologies can, however, only control one of them: radiant energy flow or privacy. Therefore, a dual-mode smart window is highly desirable. Here, we report a dual-mode switchable liquid-crystal window that can control both radiant energy flow and privacy. The switchable liquid-crystal window makes use of dielectric and flexoelectric effects. In the absence of an applied voltage, the window is clear and transparent, and radiant energy can flow through it and the scenery behind the window can be seen. When a low-frequency (50 Hz) voltage is applied, the window is switched to an optical scattering and absorbing state by a flexoelectric effect, and thus, privacy is protected. When a high-frequency (1 kHz) voltage is applied, the window is switched to an optical absorbing but nonscattering state through a dielectric effect, and thus, radiant energy flow is controlled.

We propose a p-n junction diode based on the adsorption of tetrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) molecules on a monolayer of boron phosphide (MBP). We use density functional theory and a simple tight-binding model to investigate atomic configuration, electronic properties, and transport characteristics of the TCNQ/MBP/TTF structure. The p-n mechanism is achieved by the full coverage of MBP with TCNQ and TTF molecules, which are coupled by weak van der Waals forces. The adsorption of each individual molecule on MBP provides localized electronic states close to the valence and conduction bands; this is characteristic of p- and n-type semiconductors. To understand the charge-carrier dynamics, we also examine the evaluation of energy bands, together with localized states, local potential, charge redistribution, and charge transfer under the influence of an external electric field. Our results show that the adsorption of both molecules on the surfaces of MBP results in the behavior of a p-n junction with a rectifying current through the junction in the proposed van der Waals device. Moreover, the optical response to electromagnetic radiation is also analyzed through density functional theory by considering the independent-particle approximation. We show that, with a remarkable absorption band in the infrared region, TCNQ/MBP/TTF is a potential candidate as a component of next-generation optoelectronic devices.

The successful testing of non-Abelian statistics not only serves as a milestone in fundamental physics but also provides a quantum-gate operation in topological quantum computation. An accurate and efficient readout scheme of a topological qubit is an essential step toward the experimental confirmation of non-Abelian statistics. In the current work, we propose a protocol to read out the quantum state of a Majorana vortex qubit on a topological superconductor island. The protocol consists of four Majorana zero modes trapped in spatially well-separated vortex cores on the two-dimensional surface of a Coulomb blockaded topological superconductor. Our proposed measurement is implemented by a pair of weakly coupled Majorana modes separately in touch with two normal-metal leads and the readout is realized by observing the conductance-peak location in terms of the gate voltage. Using this protocol, we can further test the non-Abelian statistics of Majorana zero modes in the two-dimensional platform. A successful readout of a Majorana qubit is a crucial step toward the future application of topological quantum computation. In addition, this Coulomb-blockaded setup can distinguish Majorana zero modes from Caroli–de Gennes–Matricon modes in vortex cores.

We present a simple protocol for which Alice and Bob must only decide to either send out a coherent state or not send out a coherent state to Charlie. No switching of bases occurs. We demonstrate that this protocol is both source-state side-channel free and measurement-device independent. We do not have to exactly control the whole space of the state of the light pulse, which is an impossible task in practice. The protocol is immune to all adverse effects caused by quantum-state imperfections in the side-channel space, such as the photon frequency spectrum, emission time, propagation direction, spatial angular momentum, and so on. Numerical simulation shows that our scheme can reach a side-channel-free result for quantum key distribution over distances exceeding 200 km, given the single-photon interference-misalignment error rate of 20%.

We theoretically, numerically and experimentally demonstrate the acoustic isolator effect in a one-dimensional waveguide with direction-dependent controlled boundary conditions. A theoretical model is used to explain the principle of nonreciprocal propagation in boundary-controlled waveguides. Numerical simulations are preformed on a reduced model to show the nonreciprocity as well as the passivity of the system through the computation of the scattering matrix and the power delivered by the system. Finally, an experimental implementation validates the potential of programmable boundary conditions for nonreciprocal propagation.

We demonstrate that the Magnus force acting on magnetic skyrmions can be efficiently tuned via modulation of the strength of spin-orbit interactions. We show that the skyrmion Hall effect, which is a direct consequence of the nonvanishing Magnus force on the magnetic structure, can be suppressed in certain limits. Our calculations show that the emergent magnetic fields in the presence of spin-orbit coupling (SOC) renormalize the Lorentz force on itinerant electrons, and thus, influence topological transport. In particular, we show that, for a Néel-type skyrmion and Bloch-type antiskyrmion, the skyrmion Hall effect (SkHE) can vanish by tuning appropriately the strength of Rashba and Dresselhaus SOCs, respectively. Our results open up alternative directions to explore in a bid to overcome the parasitic and undesirable SkHE for spintronic applications.

Nanoresonators in which mechanical vibrations and spin waves can be coupled are an intriguing concept that can be used in quantum information processing to transfer information between different states of excitation. Until now, the fabrication of freestanding magnetic nanostructures that host long-lived spin-wave excitations and may be suitable as mechanical resonators has seemed elusive. We demonstrate the fabrication of freestanding monocrystalline yttrium-iron-garnet (YIG) three-dimensional (3D) nanoresonators with nearly ideal magnetic properties. The freestanding 3D structures are obtained using a complex lithography process including room-temperature deposition and lift-off of amorphous YIG and subsequent crystallization by annealing. The crystallization nucleates from the substrate and propagates across the structure even around bends over distances of several micrometers to form, e.g., monocrystalline resonators, as shown by transmission electron microscopy. Spin-wave excitations in individual nanostructures are imaged by time-resolved scanning Kerr microscopy. The narrow line width of the magnetic excitations indicates a Gilbert damping constant of only $\alpha =2.6\times {10}^{-4}$, rivaling the best values obtained for epitaxial YIG thin-film material. The fabrication process represents a step forward in magnonics and magnon mechanics as it provides 3D YIG structures of a high quality. At the same time, it demonstrates an alternative route toward the fabrication of freestanding crystalline nanostructures, which may be applicable also to other material systems.

We investigate the spin-orbit torque in a $\mathrm{Ta}/\mathrm{Ir}\text{−}\mathrm{Mn}/\mathrm{Cu}/\mathrm{Ni}\text{−}\mathrm{Fe}$ multilayer heterostructure and relate it to spin current transmission through the $\mathrm{Ir}\text{−}\mathrm{Mn}$ layer. We identify several spin current transport regimes as a function of the temperature and the thickness of the $\mathrm{Ir}\text{−}\mathrm{Mn}$ layer. To interpret this experiment, we develope a drift-diffusion model accounting for both electron and magnon transport in the heterostructures. This model allows us to discriminate between the contributions of electrons and magnons to the total spin current in $\mathrm{Ir}\text{−}\mathrm{Mn}$. We find that the electron-magnon spin convertance is one order of magnitude larger than the interfacial electronic spin conductance, while the magnon diffusion length is about ten times longer than the electronic spin relaxation length. This study demonstrates that magnonic spin transport dominates over electronic spin transport even in disorder metallic antiferromagnets.