Dual-ring acoustic vortices carrying two orbital angular momentums are anticipated to provide new perspectives and capabilities for acoustic communication and microparticle manipulation. However, the flexible generation of a high-quality dual-ring acoustic vortex is still a challenge. Here, a hybrid-degenerated cribriform plate (HDCP) is proposed to produce a dual-ring focused acoustic vortex (FAV). The HDCP comprises L sets of circular holes arranged on L counterclockwise Fresnel spiral (FS) arms. A part of these circular holes is concurrently located on M clockwise FS-arms. Their distribution regularities on the counterclockwise and clockwise FS-arms have been analytically derived to effectively tailor the dual-ring FAVs: an outer FAV with topological charge L and an inner FAV with topological charge −M. Furthermore, an HDCP stainless steel structure is fabricated to experimentally demonstrate the generation of a dual-ring FAV. Finally, the combined action of the outer and inner FAVs is demonstrated to be able to roll a particle along an annular trajectory. The dual-ring FAVs generated by the proposed concept of HDCPs may find potential applications in particle manipulation and acoustic communication.

Magnons, the quanta of collective spin excitations in magnetic materials, may enable functionalities, such as nonreciprocity and transduction in hybrid quantum devices. To assess the potential of such applications, it is necessary to understand magnon dynamics beyond the simple harmonic oscillator regime, where theory predicts effects like population-dependent damping and quantum fluctuations in the form of magnon shot noise. Probing these phenomena requires sensors with high sensitivity and the ability to resolve magnon properties across different excitation regimes. Here, we demonstrate accurate and sensitive detection of magnon population and decay over a wide range of occupation numbers. We use a superconducting qubit to probe magnons in a ferrimagnet over approximately 2000 excitations. Using qubit control and parametrically induced qubit-magnon interactions, we demonstrate few-excitation sensitive detection of magnons with a dynamic range of approximately 30 dB, and are able to accurately resolve their decay with few-ns sensitivity. These capabilities offer a powerful and practical technique for probing magnon dynamics in or beyond the linear regime over a wide range of excitations.

In this paper, we present a model for the drift mobility tensor of a monolayer black phosphorus (phosphorene), encapsulated between two dielectrics. The model employs the energy-loss method to derive analytical expressions, accounting for pointlike charge-impurity distribution at various depths within the structure. Anisotropy, a critical factor in phosphorene-based devices, profoundly influences charge-transport properties by shaping the underlying device physics and behavior. Through the detailed analysis of various internal and external parameters, we reveal how anisotropy leads to significant differences in mobility between the armchair and zigzag directions. Both correlated and uncorrelated impurities are studied extensively and the current-voltage characteristics are derived, along with their sensitivity to the rotation angle of the phosphorene conducting channel. The longitudinal current density induced by the external electric field (along the $x$ direction) is derived under two types of boundary conditions applied in the transverse direction in the channel corresponding to a zero electric field or a zero current in the $y$ direction. This approach enables a thorough analysis of the effect of the misalignment angle of phosphorene. This work lays the foundation for the design and optimization of high-performance phosphorene-based nano- and optoelectronic devices by deepening the understanding of anisotropic charge transport.

Space-borne gravitational-wave (GW) detectors use a heterodyne laser-interferometry detection scheme due to the influence of relative motion between spacecraft. Accurate tracking of the heterodyne frequency imposes strict requirements on the performance of the spacecraft master clock, and its timing jitter noise is a limiting noise source in the phase measurement. To suppress the clock noise in data preprocessing, an interspacecraft clock-tone transfer chain in the form of phase-modulation sidebands is required. As a main component of this transfer chain, the optical power amplifier introduces excess differential phase noise between the carrier and a sideband. In this paper, we propose a scheme to measure the power amplifier differential phase noise (PADN). For this purpose, an onboard interferometer is designed by mixing the laser after power amplification with the laser before power amplification. We present the corresponding postprocessing PADN cancelation algorithm, which is compatible with the initial noise-reduction pipeline and can be directly applied to any time-delay interferometry variables.

Homogeneous magnetic fields can be generated through the strategic arrangement of permanent magnets. The Halbach array serves as a prominent example of an effective design following this principle. However, it is a two-dimensional approach because it is optimal when placing infinitely long magnets—line dipoles—on a circle. If shorter, more realistic magnets are to be used, the optimal arrangement of magnetic moments diverges from the classical Halbach geometry. This paper presents optimal solutions for three-dimensional arrangements calculated for point dipoles, including optimized orientations for single rings and stacks of two rings. They are superior to the original Halbach arrangement and a modification described in the literature, both in terms of the strength and the homogeneity of the magnetic field. Analytic formulae are provided for both cases and tested by experimental realizations.

Complex topologically nontrivial domain walls will most probably play the role of information carriers in three-dimensional magnetic nanostructures. Thus, understanding their dynamics will be crucial for their future applications. We investigate the Bloch-point domain wall stability and dynamics in cylindrical magnetic nanowires within analytical and numerical micromagnetic approaches. Our analysis demonstrates that the Bloch-point magnetization configuration is characterized by inhomogeneous helicity, nontrivial topology, and the nonzero gyrotropic vector. We show that the three-dimensional (3D) Bloch-point gyrovector is different from that for two-dimensional topological solitons, such as magnetic vortices and skyrmions. We analyze the Bloch-point domain wall velocity within the Thiele approach and demonstrate the absence of the Walker breakdown phenomenon. Under applied magnetic field parallel to the nanowire axis, no stationary regime for its dynamics exists, except a limiting case of the infinitely long nanowires. In finite-length nanowires the Bloch-point domain wall experiences a complex oscillatory hyperbolic trajectory, which may lead to its escape through the nanowire side surface. An analytical model of the domain wall is corroborated by micromagnetic modeling demonstrating the Bloch-point nonzero helicity and presenting its dynamical stability diagram. Numerical results are in agreement with the analytically predicted domain wall dynamics based on a 3D gyrovector and confirm the Bloch-point topological Hall effect similar to that found for the magnetic skymion motion. Our results are useful for engineering magnetic response of three-dimensional magnetic textures in future compact nanotechnologies.

The capability of anisotropic media to exert an optical torque on electromagnetic fields is crucial for polarization control. Here we investigate twisted layered stacks of uniaxial anisotropic media to engineer chiral mirrors for the manipulation of circularly polarized light by adjusting the layer number, thicknesses, and orientation. To this aim, we undertake a comprehensive theoretical analysis devising a multilayered twisted anisotropic photonic crystal enabling highly efficient circular polarization manipulation functionalities, i.e., showing concurring close-to-unitary helicity-preserving reflectance of one circular polarization and transmittance of the opposite one. Owing to the angular-momentum manipulation concept enabled by our proposed devices, we envisage that such chiral mirrors are promising candidates for an alternative class of integrated circular polarizers, holding great potential for applications in quantum technologies, polarization-sensitive optical detectors, and electro-optical information processing.

Exceptional points (EPs) realized in electronics have been reported to be able to merge with a divergent point in a high-order parity-time ($PT$)-symmetric system, forming the so-called divergent EP (DEP), which can provide enhanced eigenvalue bifurcation. However, such divergence makes it hard for any practical circuit to operate exactly at the DEP, resulting in large device-to-device deviations, and thus significantly degrading the sensitivity of EP sensors. To this end, we propose a method to realize the DEP by introducing cross-coupling into the $PT$-symmetric circuit. We theoretically demonstrate that by manipulation of the cross-coupling strength, the DEP destruction/restoration exhibits ultrasensitivity against the variation of the coupling between gain (loss) and neutral components. This characteristic allows the system to operate beyond the DEP to achieve enhanced sensitivity with great device consistency. Our experimental measurements verify the analytical results well, showing that the cross-coupled DEP systems exhibit superior sensitivity and device consistency compared with non-cross-coupled systems. Our work may pave the way for practical implementation DEP in diverse sensing scenarios.

Blocking transition, commonly found in magnetic solids, is little known in polar solids. We report a blocking transition of ${\mathrm{Sr}\mathrm{Ti}\mathrm{O}}_3$ (STO) surface dipoles in STO-gated ${\mathrm{Mo}\mathrm{S}}_2$ field-effect transistors. With heating above room temperature, the ferroelectriclike counterclockwise hysteresis with gate voltage in the transistor’s conductance, due to the surface dipoles of STO, peaks near 350 K. On the other hand, its transconductance rises monotonically and its response time to gate voltage decreases. The peak in hysteresis occurs at the blocking temperature where the response time matches the gate-sweep time. The blocking is used to program the dipoles’ state by gate cooling for potential memory applications.

In quantum theory, the inescapable interaction between a system and its surroundings will lead to a loss of coherence and leakage of information into the environment. One approach to retain the quantum characteristics of the system is to dynamically mitigate or eliminate the impact of the environment on the system. However, things get complicated in quantum parameter estimation tasks, especially when the unknown parameter originates from the environment. Here we propose a general dynamical modulation scheme that enables increase of estimation precision irrespective of the origin of the parameters to be estimated. Notably, beyond the capability of dynamically decoupling the system from the environment, our proposal can select the effective frequency of the system and, in turn, manipulate the dynamics of the system, such as the steady-state probability and the decay rate, which are sensitive to the bath parameter. Therefore, the quantum Fisher information is dramatically increased, leading to superior estimation precision. Specifically, we elucidate the effectiveness of our proposal with prototypical examples of Ramsey spectroscopy and the quantum thermometer. Our findings offer an alternative route to increase the precision of quantum estimation processes and may have potential applications in diverse branches of quantum metrology.

We present an electrically small Rydberg atom electric field sensor with the ability to extract the three-dimensional $k$-vector of an elliptically polarized radio-frequency field. In most mediums, the $k$-vector (or wave vector) provides the direction of propagation of an electromagnetic wave. Our method uses a field vector measurement at a single point in space and is thus compatible with a sensor volume that is arbitrarily small compared with the carrier wavelength. We measure the $k$-vector of a circularly polarized signal field with average absolute errors in the polar and azimuthal angles of 33 and 43 mrad, respectively, and statistical noise of 1.3 and 1.5 mrad/$\sqrt{\mathrm{Hz}}$, respectively. Additionally, we characterize the performance of the sensor as a function of the ellipticity of the input field and the size of the sensing region. We find that the sensor works over a broad range of ellipticities, and validate that an electrically small sensing region is optimal.

Magnetic particle spectroscopy (MPS) exploits the nonlinear dynamic magnetization of magnetic nanoparticles (MNPs) under an alternating magnetic field (AMF) to characterize both the physical properties of MNPs and their surrounding liquid environment. This technique has gained widespread application not only for characterizing MNPs but also in magnetic bioassays. Over the past 15 years, MPS-based bioassays have been developed into point-of-care devices for in-field applications, with advantages such as being inexpensive, rapid, accurate, and easy to use. However, the widespread deployment of MPS biosensors is hindered by a lack of multiplexing capability. Researchers have proposed MPS-based spatial multiplexing similar to lateral flow assays, but this approach increases the cost of materials and reagents. MPS-based spectral multiplexing, based on the assumption that the collective harmonics of a mixture of MNPs equal the harmonics of each MNP multiplied by their respective quantities, has been theoretically and experimentally demonstrated. Many studies decode the quantities of MNPs from mixtures by solving an overdetermined set of equations of harmonics through least-squares minimization. However, this can lead to decreased accuracy due to lower signal-to-noise ratios (SNRs) in higher-order harmonics. This work demonstrates that the use of a minimum number of equations to solve for unknown MNP quantities—i.e., a truncated set of equations composed of harmonic information from lower-order harmonics with higher SNR—can result in greater multiplexing accuracy. In a surface-based MPS assay mechanism, where Néel relaxations dominate the dynamic magnetizations of MNPs under an AMF, we apply our truncated set of equations to decode the quantities of different types of commercial iron oxide MNPs from a mixture. Several factors affecting multiplexing accuracy are studied, including dipolar interactions between MNPs of the same type and of different types, the choice of harmonics used in the truncated set of equations, and the amplitude and frequency of the AMF. At the end of this work, we compare the multiplexing accuracy of our method with the accuracy of the reported overdetermined system. While our method requires upfront effort in selecting appropriate harmonics for the truncated set of equations, it ultimately yields greater accuracy.

Silicon carbide is a promising material platform for hosting various color centers that are suitable for quantum information processing. Here, we report the design and demonstration of an integrated electro-optic modulator that can directly interface silicon-vacancy centers in the 4H-silicon-carbide-on-insulator platform. Despite a relatively low electro-optic coefficient ($0.22$ pm/V), the optimized silicon carbide modulator is able to work in the 920-nm range with a propagation loss of less than $0.5$ dB/cm, featuring a 3-dB bandwidth of around 500 MHz, an extinction ratio of 8–12 dB for an operating peak-to-peak voltage of 10 V, and a footprint of less than $0.1{\mathrm{mm}}^2$. With such modulation performance, this approach described provides a cost-effective solution for the chip-scale implementation of the electro-optic modulation technology required for interfacing with color centers in the silicon carbide platform.

Quantum discord represents a correlation beyond classicality that could be useful for many quantum information tasks and therefore is viewed as a valuable quantum resource. Theoretically, whether or not a bipartite quantum state has a nonzero amount of quantum discord can be determined once its density matrix is given. Experimentally, however, it is not easy to perform a reliable tomography on the state, especially when considering the imperfection of devices and the high dimensionality of the system. Here, inspired by the so-called dimension witness, we propose a new approach using uncharacterized measurements to witness quantum discord of an unknown bipartite state within an arbitrary-dimension system. Furthermore, $2\times 2$ measurements are sufficient for any bipartite state of arbitrarily large dimension. For any two-qubit state, we show that the maximum of the witness happens when one performs mutually orthogonal basis measurements on each qubit. Moreover, the witness value decreases linearly in response to the errors, which indicates its nonsensitivity to device imperfections and experimental feasibility.

Optically active solid-state spin systems have been extensively studied in quantum technologies. We introduce a new readout scheme, termed “time-to-space” (T2S) encoding, which decouples spin manipulation from optical readout both temporally and spatially. This is achieved by simultaneously controlling the spin state within a region of interest, followed by rapid scanning of the optical readout position using an acousto-optic modulator. Time tracking allows the optical readout position to be encoded as a function of time. Using nitrogen-vacancy center ensembles in diamond, we demonstrate that the T2S scheme enables correlated experiments for efficient common-mode noise cancellation in various nano- and microscale sensing scenarios. Additionally, we show scalable multipixel imaging that does not require a camera and has the potential to accelerate data acquisition by several hundred times compared to conventional scanning methods. We anticipate widespread adoption of this technique, as it requires no additional components beyond those commonly used in experiments with optically adressable spin systems.

An understanding of the interaction between bright correlated twin beams and matter is important for expanding the applications of optical quantum technology. In particular, it is worthwhile to clarify the advantages of twin-beam correlation in spectroscopic applications, since twin-beam sources that use parametric down-conversion have a wide range of wavelength tunability. Here, we theoretically and experimentally demonstrate that the spectral-focusing technique used in coherent anti-Stokes Raman scattering (CARS) can be implemented by twin beams without the use of ultrashort-pulse lasers. In typical spectral focusing using ultrashort pulses, spectral resolution is improved by narrowing the instantaneous frequency width due to frequency chirping. Similarly, we show theoretically that the formation of a chirp structure within the temporal correlation of twin beams produces an effect similar to typical spectral focusing. To experimentally demonstrate twin-beam spectral focusing, CARS spectroscopy of polyethylene is performed when the time delay between the chirped twin beams is set within the correlation width or it is set outside the correlation width. We observe that the spectral resolution is improved when the correlation is effective. By comparing with theoretical simulations, we confirm that the improvement is caused by frequency chirping.