The interplay between chains or layers, as additional degrees of freedom, provides an interesting approach to engineer the coupled modes in plasmonic arrays. In this study, we explore the application of interchain couplings to regulate the topological properties of a one-dimensional double chain composed of plasmonic ellipsoidal nanoparticles (ENPs). By aligning ENPs orthogonally in adjacent chains, we eliminate direct nearest-neighbor coupling across chains. We reveal that the distinctive interchain coupling enables the emergence of topological modes in the double chain, even though each individual chain is topologically trivial. We show that the double chain features three distinct topological phases, each characterized by a different number of topological modes safeguarded by the $Z_3$ invariant. Additionally, we demonstrate that this approach can be extended to bilayer kagome arrays, also enabling multiple topological phase transitions. Our work unveils the unique topological phases in double-chain and bilayer arrays made of anisotropic plasmonic nanoparticles. The introduction of interchain or interlayer couplings opens up other directions for manipulating the topological properties of plasmonic arrays.

High-acoustic-energy-density acoustofluidic devices are necessary to make this technology a viable option for clinical applications in the biomedical field. We present a mechanical interface that enables delivery of a high-amplitude acoustic field inside a fluid cavity by translating the vibrations from two large piezoelectric elements into a microfluidic chip. The study comprises both experimental characterization of a double-parabolic metallic acoustic waveguide and simulations of its working mechanism in two dimensions. We could focus 4.9-µm polystyrene particles at a flowrate of 5 ml/min, corresponding to an average retention time of 13.5 ms for particles in the actuated area. Moreover, we measured the acoustic energy density in the channel at stopped-flow condition, obtaining an average value of 1207 $\mathrm{J}/{\mathrm{m}}^3$ and a maximum value of 2977 $\mathrm{J}/{\mathrm{m}}^3$ with an input electrical power of 1.5 W. By comparing the simulation results with laser-Doppler vibrometer measurements, we confirmed that transverse sound waves play a significant role in the working mechanism of the double-parabolic structure, thus paving the way for further future optimization of the waveguide design.

Hyperentanglement is a promising resource in the realm of quantum communication, owing to its exploitation of multiple degrees of freedom. In this paper, we report the generation of a two-mode hyperentangled state using one nanophotonic periodically poled lithium niobate waveguide. Our approach encompasses the manipulation of polarization, energy-time, and quadrature amplitude-phase degrees of freedom. Theoretical calculations reveal that the magnitude of the Clauser-Horne-Shimony-Holt parameter $|S|$ can reach $2.375$ even considering the multi-photon-pair generation effect, which is indicative of the entanglement in the polarization degree of freedom. Further analysis involved computing the joint spectral amplitude of the two-mode state, followed by Schmidt decomposition and Fourier transformation. The resulting joint uncertainty product $\mathrm{\Delta }({\omega }_s+{\omega }_i)\mathrm{\Delta }(t_s-t_i)=0.4113$, implying that high-quality energy-time entanglement is achieved. Notably, the von Neumann entropy $S_r$ of our source reaches 0.192, confirming the presence of quadrature amplitude-phase entanglement within the generated state. Moreover, we theoretically apply our source in a free-space quantum key distribution system to demonstrate its potential to increase secret key rates. Our proposed scheme is an efficient and practical approach for facilitating high-capacity quantum communication systems.

Exciton polaritons are inherently tunable systems with an adjustable potential landscape. In this work, we show that exciton-polariton condensates can be selectively localized in a fixed optically induced periodic lattice with uniform potential depth, by judiciously controlling a second focused pump of very small size away from the lattice chain. Specifically, the localized polariton condensate can be tuned among different potential traps by adjusting the relative distance between the small pump spot and the potential lattice. The adjustment of the excitation position of the smaller pump spot and its combination with the fixed larger pump spot for the potential creation induce the mode selection determined by the gain profile, the group velocity, and the potential distribution within the system. The localization of the exciton-polariton condensate and its control are independent of the orientation of the potential lattice and, thus, even in a slightly disordered system, one can selectively excite such localized polariton condensates. Our results illuminate a path to the remote manipulation of exciton-polariton bosonic condensates in fixed integrated photonic chips and circuits.

Achieving efficient and crosstalk-free connections between components is crucial in analog devices. The recent development of topological materials within condensed matter physics has underscored their considerable potential as infrastructure for phononic and photonic analog signal processing. This is attributed to their capacity to facilitate a high degree of freedom, broadband, dispersion-free, and antireflective mechanical and electromagnetic wave transmission. The merits of this transmission warrant further exploration and extension into the domain of component connections. Here, we introduce and validate an ideal connector, termed a topological metataper, harnessing solid-state phononic crystal plates. By employing an adiabatic assembly of topological insulator interfaces with varying skin depths, the metataper sustains all the beneficial attributes of topological materials, thus enabling lossless transmission aperture switching on demand, presenting an ideal solution for connecting phononic and photonic components of varying sizes in series or parallel. This metataper also lights up as an exemplary beam-shaping technique, adept at transforming diverse incidences into coherent plane-wave emissions with predefined apertures and energy profiles. This study broadens the application of topological materials beyond waveguides, laying the groundwork for multifunctional and efficient topological photonic and phononic chips for future information processing, sensing, manipulating, and energy harvesting.

${\mathrm{Cr}\mathrm{Br}}_3$ is a promising van der Waals (vdW) material for future spintronic applications due to its unique layer stacking and multiple magnetic phases. In particular, the ability to manipulate magnetothermal properties through its structural modification makes it suitable for cooling applications in nanodevices. In this work, using the complementary modified Arrott plot, the Kouvel-Fisher method, the Widom scaling law, and critical isotherm analysis, a comprehensive analysis of critical behavior around the Curie temperature $T_{\mathrm{C}}$ is performed, and the reliable critical exponents [β = 0.245(3), γ = 1.010(6), and δ = 5.207(2)] are obtained. The critical exponents of ${\mathrm{Cr}\mathrm{Br}}_3$ satisfy the universality class of the tricritical mean-field theory, indicating that the magnetic phase transition of ${\mathrm{Cr}\mathrm{Br}}_3$ is a second-order phase transition and close to a three- to two-dimensional tricritical point near $T_{\mathrm{C}}$. Below $T_{\mathrm{C}}$, we observe a clear first-order phase transition and construct the magnetic phase diagram of ${\mathrm{Cr}\mathrm{Br}}_3$ crystals. A large and anisotropic magnetocaloric effect in ${\mathrm{Cr}\mathrm{Br}}_3$ crystals is further confirmed. The maximum magnetic entropy change $(-\mathrm{\Delta }{S}_M^{\max })$ at $T_{\mathrm{C}}$ for the out-of-plane and in-plane directions are 6.72 and 6.55 J ${\mathrm{kg}}^{-1}$ ${\mathrm{K}}^{-1}$, respectively. Additionally, the relative cooling powers in these directions are 137.51 and 133.46 J ${\mathrm{kg}}^{-1}$ at 5 T, underscoring the magnetic cooling application of ${\mathrm{Cr}\mathrm{Br}}_3$. Our findings on ${\mathrm{Cr}\mathrm{Br}}_3$ not only provide an in-depth understanding of the magnetic phase transition, but also indicate potential applications in magnetic refrigeration.

Platforms based on transmission lines are nowadays employed for the simulation of standard phenomena in quantum electrodynamics and quantum field theory. In this work, we propose a hybrid platform, in which a right-handed transmission line is connected to a left-handed transmission line by means of a superconducting quantum interference device. We examine the interaction between the two transmission lines, as well as the excitation flow along the composite platform. We show that, by activating specific resonance conditions, this platform can be used as a quantum simulator of different phenomena in quantum optics, multimode quantum systems, and quantum thermodynamics.

Metallic meshes have long demonstrated outstanding electromagnetic shielding capabilities against low-frequency electromagnetic waves, facilitating vital applications like Faraday cages. Here, we demonstrate a metallic metamesh with tailored metallic patterns that is conducting like normal metallic meshes, but also exhibits remarkable perfect transparency for arbitrary electromagnetic waves at the working frequency. Based on special resonances introduced by the designed composite structures, such metameshes have achieved omnidirectional impedance matching with free space, regardless of the polarization and incident angle. This property enables near-100% transmission through the metamesh, with unchanged wave front. This transition from electromagnetic shielding to perfect transparency has been validated through both numerical simulations and microwave experiments. Our work paves the way towards realizing metastructures that are both conducting and transparent to electromagnetic waves, opening possibilities in radomes and wireless communications.

Long-range coupling is usually much weaker than nearest-neighbor coupling, and achieving stronger long-range coupling is challenging. Recently, a unique topological phase induced by strong long-range coupling has been proposed and experimentally demonstrated in quadrupole topological insulators with both positive and negative couplings. Here, we propose a new higher-order topological insulator protected by the multipole chiral number in a two-dimensional Su-Schrieffer-Heeger model by introducing strong third-nearest-neighbor couplings and requiring only positive couplings. We design and fabricate a waterborne acoustic crystal, which consists of through holes and grooves in a copper plate, to realize this topological material. The near-field response spectra and pressure field distributions provide evidence for the existence of multiple zero-dimensional topological corner states within the bulk gap. Interestingly, as an application, we further demonstrate the trapping of polystyrene particles by utilizing the highly localized pressure fields of the multiple corner states. Our work offers a feasible acoustic topological device to manipulate corner states as well as particles and is expected to have potential applications in acoustic sensing and acoustic tweezers.

Artificially introducing periodic patterns into magnetic materials can manipulate spin waves (SWs) with rich band structures. Incorporating a magnetochiral mechanism into magnonic crystals (MCs) unlocks nonreciprocal properties in SWs, further enhancing their potential applications. Here, we comprehensively investigate the SW band structures of bicomponent chiral MCs by periodically tailoring the intensity of the interfacial Dzyaloshinskii-Moriya interaction (iDMI) in heavy metal/ferromagnetic/heavy metal trilayer systems [${\mathrm{HM}}_1/\mathrm{FM}/{\mathrm{HM}}_{1(2)}$]. Notably, a flat band structure with zero group velocity, originating from the robust localization of magnon modes, can be found by tuning the effective iDMI energy. Meanwhile, the nonreciprocal properties in these MCs can be significantly enhanced with increasing the effective iDMI energy, facilitating the unidirectional propagation of SWs. Moreover, both the width and position of the indirect band gap in our MCs are easily tuned and closely related to the iDMI, lattice period, and/or external magnetic field. The wave-vector difference between the top of the first band and the bottom of the second band increases linearly with the effective iDMI energy. Both frequency-domain finite-element method calculations and finite-difference time-domain micromagnetic simulations agree well with the experimental observations. This study provides insights and methodologies for designing SW-based nanodevices.

The generation of acoustic vortices across various spatial domains is crucial for many orbital angular momentum (OAM) applications. Traditional methods, however, are restricted by the conventional OAM conservation law, limiting their capability to generate vortices solely within either transmission or reflection spaces. Here, we propose an approach that circumvents this limitation through a hybrid design integrating a phase-gradient metasurface with an OAM filter. We reveal that asymmetric OAM transition, achieved through the synergistic interplay of OAM tunneling via the filter and OAM diffraction mediated by the metasurface, overcomes the conventional constraints, allowing for direction-dependent OAM generation. This facilitates precise and arbitrary control of spatial energy distribution of generating vortices, leading to the OAM generation in arbitrary transmission and reflection spaces. Experiments are conducted to validate these findings. This work presents an alternative strategy for realizing diverse OAM generation or asymmetric propagation, thereby expanding current capabilities of acoustic OAM applications.

Revealing the expansion and interaction dynamics of multiple cavitation bubbles (MCBs) induced by nanosecond lasers is essential for advancing fields such as biomedicine. However, these interactions are highly complex and challenging to control, necessitating further investigation to elucidate the specific dynamic principles governing these processes. We report experimental and theoretical investigations into the strong-interaction dynamics of millimeter-sized MCBs. An analytical model with the initial velocity of the cavitation bubbles as input is used to retrieve the distance and position between the bubble walls from the experimental results. Additionally, by developing appropriate physical models, we have elucidated the overpressure-limited and inertia-controlled modes during the interactions of MCBs. The predicted bubble-wall extrusion lengths during expansion agree well with the experimental data, indicating that inertia dominates the coalescence of MCBs in the later stages of expansion. Subsequently, theoretical calculations using the dynamic equilibrium model, with the expansion radius and retrusion angle of cavitation bubbles as input parameters, have been employed to estimate the coalescence time of MCBs. Our research provides a potential theoretical reference for understanding the strong-interaction process between MCBs in water.

The organic flashing-ratchet experiment demonstrates that current can be measured even in the absence of a net bias. Motivated by these experiments, we employ the Marcus theory to simulate the charge-hopping process under a time-varying, nonuniform electric field without a net driving force. Our findings indicate that directional motion is observed only when both temporal and spatial conditions are satisfied simultaneously, namely time-dependent flashing and spatial asymmetry in the ratchet potential. The ratchet current can be optimized by selecting a specific flashing frequency and spatial structure. In addition, we discuss both the temperature effect and the anisotropic effect of the flashing ratchet, allowing the current of an actual device to be predicted. The presence of a time-varying and spatially nonuniform electric field in organic photoelectric devices suggests that the flashing-ratchet effect is an intrinsic property of these devices. Based on this, our research opens up a robust routine for designing the intrinsic electric field to enhance the performance of optoelectronic devices.

We propose and demonstrate a quantitative noncontact measurement method for the thermal Hall effect (THE) based on magnetic-field-modulated lock-in thermography (LIT). This method enables visualization of THE-induced temperature change and quantitative estimation of the thermal Hall angle θ${}_{\mathrm{THE}}$ by applying periodic magnetic fields to a sample and obtaining the first-harmonic response of thermal images. By combining this method with LIT-based measurement techniques for the longitudinal thermal conductivity κ${}_{xx}$, we also quantify the transverse thermal conductivity κ${}_{xy}$. We validate our measurement methods by estimating θ${}_{\mathrm{THE}}$, κ${}_{xx}$, and κ${}_{xy}$ in a ferromagnetic Heusler alloy ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Ga}$ slab showing large THE.

Superconducting qubits are a key contender for quantum computing elements, but they often face challenges like noise and decoherence from two-level systems (TLSs). Tantalum ($\mathrm{Ta}$) qubits are notable for their long $T_1$ coherence times, nearing milliseconds, presumably due to fewer TLSs, though the cause of this is unclear. We explore this by analyzing the vacuum-oxide interface using density functional theory, particularly comparing $\mathrm{Nb}$ oxide (${\mathrm{Nb}}_2{\mathrm{O}}_5$) and $\mathrm{Ta}$ oxide (${\mathrm{Ta}}_2{\mathrm{O}}_5$). We discover that ${\mathrm{Ta}}_2{\mathrm{O}}_5$ forms a smoother surface with fewer dangling $\mathrm{O}$ atoms and structural TLSs than ${\mathrm{Nb}}_2{\mathrm{O}}_5$. The greater atomic mass of $\mathrm{Ta}$ also lowers the tunnel splittings of these structural TLSs below the qubit’s operating frequency. Furthermore, using external electric fields or ${\mathrm{SO}}_2$ passivation can significantly reduce defect-related TLSs on $\mathrm{Nb}$ surfaces, potentially improving their coherence times.

Nanopillars are widely used for various applications and require accurate shape characterization to enhance their performance and optimize fabrication processes. In this paper, we employ coherent Fourier scatterometry (CFS) combined with rigorous three-dimensional finite-difference time-domain simulations to accurately determine the shapes of nanopillars with various geometries, including cylindrical, triangular, square, and rectangular shapes. The nanopillars considered here have lateral dimensions ($a$) ranging from 100 to 1000 nm. Our methodology utilizes the preferential excitation of the nanostructures by a tightly focused beam and leverages their inherent symmetry to capture far-field signatures that vary periodically with rotation. This approach allows us to distinguish between different nanopillar shapes based on these rotational signatures. Our results demonstrate that the CFS method can reliably characterize nanopillars with lateral dimensions $a\ge 300$ nm, surpassing the conventional diffraction limit of 351 nm. However, the method reaches its fundamental limits for $a\le 200$ nm, as also confirmed by simulations, where we approach the dipole approximation regime ($a\ll \lambda$). This constraint is not observed for rectangular nanopillars, owing to their constant breadth ($b=1000$ nm), which prevents such a regime. Furthermore, our method successfully differentiates nanopillars transitioning from rectangular to square shapes. We also explored the method’s limitations concerning nanostructure height ($h$), finding that triangular and square nanopillars could be characterized accurately for $h\ge 50$ nm and $h\ge 150$ nm, respectively. Furthermore, the method remains robust against shape distortions such as edge roundness. The method is primarily effective in determining the lateral (top-down) shape of nanopillars, it does not resolve longitudinal features. The ability to accurately characterize nanostructure shapes has significant implications in fields such as photonics and biosensing, where geometry critically influences device performance.

Shortcuts to adiabaticity (STA) enables fast and robust coherent control of quantum system, which has been well placed in quantum technologies. In particular, inverse-engineering STA provides much more freedom for the optimization of shortcut, which alleviates the complexity for experimental realization. Here, we implement a STA technique, known as invariant-based inverse engineering, to speed up the adiabatic control of the electron triplet ground state of a single nitrogen-vacancy (N-$V$) center. The microwave pulses to drive inversely engineered STA are obtained with space-curve quantum control, where the evolution of spin transition is mapped to a three-dimensional closed space curve and the design of shortcut is obtained by optimization over the space curve. We demonstrate the fast and high-fidelity drive of dipole-forbidden transition between two spin sublevels of the ground state. Moreover, we demonstrate the robustness of the spin transition by introducing the detuning of driving microwave field. The acceleration and robustness is further confirmed by the comparison with two traditional Raman control schemes. Our results suggest invariant-based inverse engineering is powerful for fast and robust manipulation of N-$V$ system, and thus benefits quantum sensing and quantum computation based on the N-$V$ platform.

Integrated photonics plays a pivotal role in quantum communication devices, offering exceptional robustness, scalability, and performance. The growing maturity of silicon photonics technology offers significant potential for miniaturization and cost-effective implementation of quantum key distribution (QKD). While the practical security of lithium niobate modulators in QKD systems has been extensively examined, the adoption of a new modulation mechanism by silicon photonic modulators necessitates a thorough investigation into their impact on the security of QKD systems. For the first time, we reveal that the two-photon absorption effect in silicon photonic intensity modulators will introduce vulnerabilities, enabling an eavesdropper (Eve) to execute malicious attacks on QKD systems. Through experimental demonstration, we show that by externally injecting femtosecond pulses, Eve can manipulate the intensities of decoy states sent by legitimate users. Based on the experimental results, we find that in the presence of the attack, legitimate users consistently overestimate the secret key rate predicted by the security proof. Our work represents an initial exploration into a new security aspect for the design and standardization of integrated QKD systems.