In this article, we propose a passive parity-time (PT)-symmetric metasurface mirror composed of only a lossy stepped waveguide per period, exhibiting perfect retroflection for positive incidence (PI) but perfect absorption for negative incidence (NI) at the exceptional point. The mechanism underlying the extreme asymmetry is the unilateral excitation of the evanescent wave and the waveguide mode. In addition, by combining two pieces of the established passive PT-symmetric metasurface mirrors, the incident wave for NI absorbed by one of the established passive PT-symmetric metasurface mirrors can be recovered by the other. Thus, a passive PT-symmetric metasurface with balanced "loss" and "gain" is constructed, exhibiting perfect retroflection for PI but perfect transmission for NI. This work extensively simplifies the design of the PT-symmetric metasurface, and may stimulate the development of asymmetric response engineering in compact acoustic devices.

Acoustic metasurface-based vortex generators have shown effective feasibility, yet they remain constrained by limited bandwidth or fixed functionality. Here, we propose a reconfigurable multilayered (RM) metasurface capable of dynamically manipulating acoustic vortices over a broadband frequency range. The RM metasurface comprises eight sector-shaped units and is placed into a circular waveguide supporting a maximum topological charge of l(M) = 1. Each sector-shaped unit is built upon the designed coiling structure and consists of two auxiliary layers and one functional layer with rotatable blades. Dynamic reconfiguration of the intrinsic topological charge (l(xi)) in RM metasurface is achieved by rotating the blades in the functional layer of each sector-shaped unit. Simulation results confirm that across the frequency range of 3.1-3.9 kHz, the tunable l(xi) enables the conversion of an incident acoustic plane wave into multiple acoustic vortex states. This work balances the broadband operation and tunable functionality in acoustic vortex generation, providing a promising platform for practical acoustic vortex-based applications.

In nonequilibrium quantum systems, the quantum Mpemba effect (QME) emerges as a counterintuitive phenomenon: Systems exhibiting greater initial symmetry breaking restore symmetry faster. It has been attracting broad interest in studying QME dynamics and potential applications in quantum information science. While theoretical exploration of QME has surged, experimental studies, specifically on its flexible modulation, remain limited. Here, we report the observation and modulation of QME using a superconducting processor featuring an all-to-all connected, tunable-coupling architecture that enables precise control from short-to long-range interactions. This platform allows independent manipulation of coupling regimes, on-site potentials, and initial states, enabling us to elucidate their roles in QME. To quantify symmetry restoration, we employ entanglement asymmetry (EA), derived from the reconstructed density matrix via quantum state tomography, as a sensitive probe. In strong short-range coupling regimes, EA crossovers during quenches from tilted Neel states confirm the presence of QME. In contrast, in intermediate-coupling regimes, synchronized EA and entanglement entropy dynamics reveal the suppression of QME. Remarkably, QME reemerges with the introduction of on-site linear potentials or quenches from tilted ferromagnetic states, the latter proving robust against on-site disorder. Our study demonstrates flexible QME modulation on a superconducting platform with multiple controllable parameters, shedding light on quantum many-body nonequilibrium dynamics and opening avenues for quantum information applications.

Topological phases are robust against weak perturbations, but break down when disorder becomes sufficiently strong. However, moderate disorder can also induce topologically nontrivial phases. Thouless pumping, as a (1+1)D counterpart of the integer quantum Hall effect, is one of the simplest manifestations of topology. Here, we report experimental observations of the competition and interplay between Thouless pumping and disorder on a 41-qubit superconducting quantum processor. We improve a Floquet engineering technique to realize cycles of adiabatic pumping by simultaneously varying the on-site potentials and the hopping couplings. We demonstrate Thouless pumping in the presence of disorder and show its breakdown as the strength of disorder increases. Moreover, we observe two types of topological pumping that are induced by on-site potential disorder and hopping disorder, respectively. In particular, an intrinsic topological pump that is induced by quasi-periodic hopping disorder has never been experimentally realized before. Our highly controllable system provides a valuable quantum simulating platform for studying various aspects of topological physics in the presence of disorder.

Recently, various metamaterial-based harvesters have been investigated for harvesting electromagnetic energy from the ambient environment. However, they suffer from narrow absorption bandwidths and low energy harvesting efficiency. In this paper, we propose a miniaturized dual-layer metasurface designed for harvesting ambient electromagnetic energy, featuring wide-angle responsivity and polarization-insensitivity. The metasurface comprises two metal rings and two layers of dielectric substrates. The results demonstrate that the harvester functions within the S- and C-bands, resonating at frequencies of 2.98GHz and 4.32GHz, respectively. These resonant frequencies induce electric dipole oscillations, facilitating strong absorption of electromagnetic waves. The harvesting efficiency can reach to 92.5% and 93.4% at the two frequencies. Moreover, the harvester performance over a wide range of incidence angles and various polarized angles of the incident wave is analyzed. The harvester can be used for harvesting the redundant electromagnetic energy of communications or radars in the future.

Dynamically switchable acoustic propagation shows potential applications in noise control and medical engineering. Even if the reconfigurable metasurfaces (RMs) have been proposed to switch on/off acoustic propagation, the narrow working frequency and restricted incident angle limit the potential applications. To overcome the limitations, a RM with adjustable refractive index profile is designed in a frequency broadband. By adjusting the refractive index profile of the RM, both theoretical analysis and numerical simulations demonstrate that the proposed RM can effectively switch on and off acoustic propagation in the frequency range [2.9-4.1 kHz] and incident angle range [0 degrees-60 degrees]. The underlying mechanism originates from the diffraction law of phase gradient metagrating, where the refractive index modulation of the RM enables precise control over acoustic diffraction phenomena. The proposal features broadband and large incident angle range, and would contribute to the acoustic barriers and medical ultrasound therapy.

OBJECTIVE:This study aims to investigate the feasibility of ultrasound technology for assessing muscle atrophy progression in a head-down bed rest model, providing a reference for monitoring muscle functional status in a microgravity environment. METHODS:A 40-day head-down bed rest model using rhesus monkeys was established to simulate the microgravity environment in space. A dual-encoder parallel deep learning model was developed to extract features from B-mode ultrasound images and radiofrequency signals separately. Additionally, an up-sampling module incorporating the Coordinate Attention mechanism and the Pixel-attention-guided fusion module was designed to enhance direction and position awareness, as well as improve the recognition of target boundaries and detailed features. The evaluation efficacy of single ultrasound signals and fused signals was compared. RESULTS:The assessment accuracy reached approximately 87% through inter-individual cross-validation in 6 rhesus monkeys. The fusion of ultrasound signals significantly enhanced classification performance compared to using single modalities, such as B-mode images or radiofrequency signals. CONCLUSION:This study demonstrates that ultrasound technology combined with deep learning algorithms can effectively assess disuse muscle atrophy. The proposed approach offers a promising reference for diagnosing muscle atrophy under long-term immobilization, with significant application value and potential for widespread adoption.

Aims: Shear wave elastography (SWE) is of great significance in measuring the elasticity and in evaluating mechanical properties of biological tissues. The elasticity of biological tissues can be reflected by measuring the propagation velocity of shear waves. Therefore, accurate estimation of shear wave velocity is crucial.Material and methods: In this study, we proposed a robust estimation method based on a cyclic shifting algorithm (CSA) for measuring shear wave group velocity in homogeneous media. To validate the utility of the algorithm, we conducted accuracy analysis and robustness analysis with different noise levels in the digital phantom used for the standardization of shear wave velocity by Quantitative Imaging Biomarker Alliance (QIBA) of the Radiological Society of North America.Results: The estimated shear wave velocities (SWV) of the elastic digital phantoms with Young’s moduli 3 kPa, 6 kPa, 15 kPa, 30 kPa are 1.0156 m/s, 1.4065 m/s, 2.1875 m/s, 3.1250 m/s, respectively. When adding Gaussian white noise with 0 dB, the relative errors of the estimated SWVs are 2.5%, 4.8%, 11.8%, 20.5%, respectively. The estimated SWVs in the gelatin phantom with gelatin concentration of 7% and 10% are 2.0442 m/s and 3.1237 m/s. Compared with the existing two representative estimation algorithms, the estimation algorithm proposed in this paper has a higher anti-noise performance due to effective energy accumulation in the frequency domain.Conclusions: The proposed SWV method based on CSA in frequency domain is a robust shear wave group velocity estimation method, which seems to be a useful tool in homogeneous media for ultrasound elastography.

Abstract Photoacoustic (PA) imaging owns a great prospect in medical diagnosis because of its high contrast and capability in functional imaging. While, the detected PA signals are always a mix of direct-arrived signals (DAS) and reflected (scattered) signals (RS) in inhomogeneous and bounded samples such as human tissues. The RS can lead to many artifacts and severely affect the final image, which confuses the artifacts with the real PA sources. This paper employed a spatial singular value decomposition (SVD) filter to abstract the DAS and thus remove the reflection artifacts. We conducted experiments on an agar phantom and an in vitro tissue to verify the method. The results show that the proposed method can effectively remove RS, resulting in fewer reflection artifacts in PA images.

In superconducting qubit systems, microwave crosstalk among the qubit control lines is a prominent source of errors for gate operations, particularly when implemented simultaneously in a multiqubit system. In this work, we present an experimental study of crosstalk mitigation for the case of single-qubit gate operation, which involves the universal U3 gate decomposition into two Xπ/2 gates and three virtual Z gates. We demonstrate that by optimizing the virtual Z gate parameters, the crosstalk can be effectively mitigated, with the single-qubit gate fidelity recovered to the level comparable to that in the absence of crosstalk.

Hyperbranched polyimides (HBPIs) possess a unique branched structure, which can make the lowest unoccupied molecular orbitals (LUMOs) degenerate and reduce the bandgap between the highest occupied molecular orbital (HOMO) and LUMO energy levels. The triazole group can facilitate the charge transfer process. Thus, a novel hyperbranched polyimide (HBPI-TZA-6FDA) has been prepared from new triazole derivative triamine monomer (TZA) and 4,4 '-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) for memory device. The memory device with the structure ITO/HBPI-TZA-6FDA/Al exhibits a low-threshold voltage of -2.2 V and a high ON/OFF current ratio of about 105. Meanwhile, the memory device shows nonvolatile write once read many times (WORM) type memory behavior and excellent stability with an operation time of 104 at a continuous applied voltage of -1 V. Optical, electrochemical experiments, and molecular simulation have been carried out to illustrate the memory performance. The memory performance is governed by the charge transfer between TZA and 6FDA units. The branched structure and triazole unit can reduce the band gap between HOMO and LUMO energy levels effectively, which is favorable for improving charge transfer and reducing threshold voltage. The HBPI-TZA-6FDA-based memory device is favorable for memory device applications due to its relatively low-power consumption and high-operation stability. image

Abstract Sound field visualization of specified frequency is an essential method for acoustic studies, especially in nonlinear acoustics. In this paper, we designed a sound field visualization system of specified frequency (SVSF). By combining the traditional sound field scanning system with the lock-in amplifier (LIA), the SVSF can visualize the amplitude distribution of multiple arbitrary specified frequencies with only one-time sound field scanning. Further, depending on the SVSF, we analysed the nonlinear acoustic effects around the focus of a spherical coronal ultrasonic transducer array. The excitation signal is a sinusoidal signal at 40 kHz. The results show that the acoustic waves at the focus contain fundamental frequencies at 40 kHz and harmonic frequencies at 80 kHz, 120 kHz, and 160 kHz. Comparing the amplitude distribution of those frequencies, we found that higher harmonics own smaller focus areas as well as lower amplitude, which conforms to the nonlinear acoustic theory. The system is convenient for those similar studies involving the multi-frequency amplitude field comparison.

Chiral metal nanoclusters (MNCs) are competitive candidates for fabricating circularly polarized light-emitting diodes (CPLEDs), but the device performance is greatly limited by the poor emission of MNCs in solid thin films. Herein, host molecule enhanced aggregation induced emission (AIE) of MNCs is demonstrated for fabricating highly efficient CPLEDs. Namely, on the basis of the AIE effect of atomically precise enantiomeric (R/S)-4-phenylthiazolidine-2-thione capped silver (R/S-Ag6(PTLT)6) NCs in solid thin films, 1,3-bis(carbazol-9-yl) benzene (mCP) is introduced as a host molecule to control the orientation and packing arrangements of R/S-Ag6(PTLT)6 NCs through π—π interactions with the R/S-Ag6(PTLT)6 NCs and further enhance the AIE. The as-fabricated Ag6(PTLT)6 NC/mCP hybrid solid thin film shows a high photoluminescence quantum yield of 71.0

Two-dimensional (2D) BiVO4 nanosheets (NSs), featuring distinctive chemical properties and dangling-bond-rich surfaces, are promising for developing high-performance gas sensors. However, the previously reported 2D BiVO4 NSs-based devices suffer from a low responsivity and poor selectivity. Here, catalytic metal (Pt) nanoparticles (NPs) are functionalized on the surface of BiVO4 NSs to improve the sensing ability. Comparative investigations verify the significant enhancement in acetone sensing after Pt modification. The Pt NPs-loaded BiVO4 exhibits a response of 12.5-100 ppm acetone, which is 3.2 times higher than that of pure BiVO4 sensor. Besides, the Pt-BiVO4 sensor possesses better selectivity and lower detection limit. From both the experimental results and density functional theory (DFT) calculation, the effects of Pt modification are elucidated as a synergy of chemical and electronic sensitization. The loading of Pt benefits the thickening of electron depletion layer, and accumulating and activating the acetone molecules, which accelerate the reaction between acetone and chemisorbed oxygen species, resulting in enhanced sensing performance. This work gives deep insights into the effects of noble metal modification on metal oxide-based sensing material and could serve as a guideline for further designing novel high-performance sensing materials.

Lead-free double perovskite nanocrystals (LFDP NCs) are promising materials for illumination and display ap-plications because of their potential to overcome the toxicity and instability of lead-based counterparts. Despite the success in the synthesis of LFDP NCs, tunable control over the photoluminescence (PL) of LFDP NCs is still challenging. Herein, brightly emissive and stable Rb+, Sb3+-codoped Cs2NaInCl6 NCs are synthesized while fulfilling tunable self-trapped exciton (STE) emission in the blue region through the A, B-site codoping strategy. Sb3+ is introduced into the B-site of Cs2NaInCl6 NCs to break the parity-forbidden transition and boost the emission efficiency. By further altering the amount of A-site doped Rb+, the emission peak of the NCs is tunable from 447 to 528 nm, because Rb+ enlarges the electron-phonon coupling energy, which leads to larger Stokes shifts and therefore the continuous red-shift of PL emission. The Rb+, Sb3+-codoped Cs2NaInCl6 NCs exhibit robust PL and phase stability against moisture after one year of storage. A series of LFDP NCs with tunable emission are synthesized according to the codoping strategy and further employed as the color conversion materials for fabricating light-emitting diodes.

Quantum quench is a typical protocol in the study of nonequilibrium dynamics of quantum many-body systems. Recently, a number of experiments with superconducting transmon qubits are reported, in which the spin and hard-core boson models with two energy levels on individual sites are used. The transmons are a multilevel system and the coupled qubits are governed by the Bose-Hubbard model. How well they can be approximated by a two-level system has been discussed and analysed in different ways for specific experiments in the literature. Here, we numerically investigate the accuracy and validity of the two-level approximation for the multilevel transmons based on the concept of Loschmidt echo. Using this method, we are able to calculate the fidelity decay (i.e., the time-dependent overlap of evolving wave functions) due to the state leakage to transmon high energy levels. We present the results for different system Hamiltonians with various initial states, qubit coupling strength, and external driving, and for two kinds of quantum quench experiments with time reversal and time evolution in one direction. We show quantitatively the extent to which the fidelity decays with time for changing coupling strength (or on-site interaction over coupling strength) and filled particle number or locations in the initial states under specific system Hamiltonians, which may serve as a way for assessing the two-level approximation of transmons. Finally, we compare our results with the reported experiments using transmon qubits.

We have proposed and experimentally verified a tunable inter-qubit coupling scheme for large-scale integration of superconducting qubits. The key feature of the scheme is the insertion of connecting pads between qubit and tunable coupling element. In such a way, the distance between two qubits can be increased considerably to a few millimeters, leaving enough space for arranging control lines, readout resonators and other necessary structures. The increased inter-qubit distance provides more wiring space for flip-chip process and reduces crosstalk between qubits and from control lines to qubits. We use the term Tunable Coupler with Capacitively Connecting Pad (TCCP) to name the tunable coupling part that consists of a transmon coupler and capacitively connecting pads. With the different placement of connecting pads, different TCCP architectures can be realized. We have designed and fabricated a few multi-qubit devices in which TCCP is used for coupling. The measured results show that the performance of the qubits coupled by the TCCP, such as T_1 and T_2, was similar to that of the traditional transmon qubits without TCCP. Meanwhile, our TCCP also exhibited a wide tunable range of the effective coupling strength and a low residual ZZ interaction between the qubits by properly tuning the parameters on the design. Finally, we successfully implemented an adiabatic CZ gate with TCCP. Furthermore, by introducing TCCP, we also discuss the realization of the flip-chip process and tunable coupling qubits between different chips.

Redox imbalance can trigger cell dysfunction and damage and plays a vital role in the origin and progression of many diseases. Maintaining the balance between oxidants and antioxidants in vivo is a complicated and arduous task, leading to ongoing research into the construction of redox nanomaterials. Nanodrug platforms with redox characteristics can not only reduce the adverse effects of oxidative stress on tissues by removing excess oxidants from the body but also have multienzyme-like activity, which can play a cytotoxic role in tumor tissues through the catalytic oxidation of their substrates to produce harmful reactive oxygen species such as hydroxyl radicals. In this review, various redox nanomaterials currently used in disease therapy are discussed, emphasizing the treatment methods and their applications in tumors and other human tissues. Finally, the limitations of the current clinical application of redox nanomaterials are considered.

The nonlinear effect of high-intensity sound waves produces the acoustic radiation force (ARF), which are used for acoustic levitation and manipulation practical. With no special requirement for the physical and chemical properties of the controlled objects, acoustic levitation owns a promising application prospect. The common levitation scheme includes the standing-wave system and phased-array levitation system. The standing-wave system has poor performance in the aspects of the degree of spatial freedom, the ARF along the non-axial direction, and the levitation stability. The phased-array system requires a complex control system and a high production cost. Here, we propose a single-side acoustic levitation system based on the paired confocal focused transducers. By driving the transducer pairs with reverse phase mode, two anti-phase focused spherical waves interfere with each other, resulting in constant sound pressure of 0 Pa at the focus. The resulting potential well can achieve stable particle capturing and levitating. First, we verifed the theoretical feasibility of the system according to Huygens' principle. Then, using the finite element method, we analyzed the influences of structural and driving parameters on the sound field distribution, such as the angle between the transducer axis and the central axis of the structure and the excitation phase modes. Finally, we demonstrated the particle trappings under two kinds of excitation phase modes of the levitation system experimentally. The results show that, 1) the intensity of the dominating potential well reaches a strongest value when the structural angle is 45°; 2) as the excitation phases are 0, 0, π, and π, the sound field owns three potential wells which can capture three clusters of quartz sands, the primary potential well is stronger than the secondary one; 3) as the excitation phases are 0, π/2, π, and 3π/2, the sound field owns one potential well and captures one cluster of quartz sands. The isosurface of wave intensity around the potential well is more comprehensive than in the previous phase mode. The four-phase excitation improves the levitation stability better. The proposed levitation scheme can realize stable single- or multi-position capture of high-density objects in the fluid. Moreover, it has the advantages of low cost and a high degree of freedom.