Optical circular dichroism (CD) is a useful method for investigating the role of chirality in natural and physical processes. A large magnitude of CD must be achieved for spectroscopy and sensing, particularly in the ultraviolet (UV) energy range where molecular chirality is identifiable. However, the strong absorption of UV wavelengths in many materials precludes large UV-CD responses. In this work, we observed a giant temperature-independent magnetic circular dichroism (MCD) in the UV regime in magnetic ${\mathrm{Co}}_2\mathrm{Mn}\mathrm{Ga}$ thin films. We demonstrated the MCD in this system is controlled by the magnetization and originates from the hybridization of Co and Mn $3\mathit{\text{d}}$ states, by referring to calculations of the spin-polarized density of states. Based on these results, we propose and test two general rules for identifying other magnetic materials expected to have large MCD. Our results open a route towards finding magnetic materials with large MCD excited at different energy ranges, for CD applications with immunity to temperature variation.

Topological superconductors with topological surface states and strong spin-orbit coupling present exciting opportunities for fault-tolerant quantum computing and advanced spintronic applications. Among the few identified topological superconductors, β-${\mathrm{Bi}}_2\mathrm{Pd}$ is of particular interest for spintronic applications since it hosts superconductivity with spin-triplet pairing, offering the prospect of lossless spin supercurrent with infinite spin diffusion length. In this work, we explore the spin current phenomena in β-${\mathrm{Bi}}_2\mathrm{Pd}$ at room temperature. Through harmonic Hall and spin Hall magnetoresistance measurements, we reveal substantial, reliable, and robust charge-to-spin conversion in β-${\mathrm{Bi}}_2\mathrm{Pd}$. In particular, spin current phenomena exhibit a strong dependence on the crystalline order of β-${\mathrm{Bi}}_2\mathrm{Pd}$, underscoring the critical role of crystal integrity in shaping its topological states. Furthermore, we showcase energy-efficient spin-orbit torque switching in β-${\mathrm{Bi}}_2\mathrm{Pd}$-based spintronic devices. These findings position β-${\mathrm{Bi}}_2\mathrm{Pd}$ as a versatile and robust platform for spin current transport and lay the foundation for exploring spin supercurrent for advanced topological spintronic applications.

Understanding swimming in soft yielding media is challenging due to their complex deformation response to the swimmer’s motion. We experimentally show that a scallop-inspired swimmer with reciprocally flapping wings generates locomotion in granular matter. This disagrees with the scallop theorem prohibiting reciprocal swimming in a liquid when its inertia is negligible. We use x-ray tomography and laser profilometry to show that the propulsion is created by the combined effects of jamming and convection of particles near the wings, which break the symmetry in packing density, surface deformation, and kinematics of the granular medium between an opening and a closing stroke.

Nowadays, for experiments on microscopic imaging and ultrafast dynamics, precise and complete detection of multihit signals is indispensable. Demand for the discrimination of multiple particles that are simultaneously detected is growing for scientific purposes, such as probing electron-electron correlations and Coulomb explosion imaging. The particles collected with nearly the same arrival times will generate overlapping pile-up signals, which may cause signal loss or misjudgment. Here, we propose a method employing convolutional neural networks to accurately discriminate pile-up signals. This method is demonstrated with experimental photoionization data and achieves nearly an order of magnitude reduction in channel dead time for delay-line detectors. Moreover, this method has the potential to expand the applications of other kinds of detectors in various scientific fields.

Material disorders are one of the major sources of noise and loss in solid-state quantum devices, whose behaviors are often modeled as two-level systems (TLSs) formed by charge tunneling between neighboring sites. However, the role of their spins in tunneling and its impact on device performance remain highly unexplored. In this work, employing thin $\mathrm{Ti}\mathrm{N}$ superconducting resonators, we reveal anomalous TLS behaviors by demonstrating an unexpected increase in resonant frequency at low magnetic fields. Furthermore, a spin-flip TLS model is proposed, in which an effective spin-orbit coupling is generated by inhomogeneous local magnetic fields from defect spins. This mechanism mixes charge tunnelings and spin flips, quantitatively reproducing the observed frequency-field relationship and its temperature dependence. This work deepens the understanding of spin-dependent TLS behaviors, offering the possibility of magnetically engineering noise and loss in solid-state quantum devices.

Perpendicular switching of a ferromagnet induced by spin torques is crucial for building high-density spin-based memory and logic devices, where out-of-plane spin polarization (${\sigma }_z$) has become a long-sought-after goal for deterministic switching without assisted magnetic fields. Here, we report the observation of ${\sigma }_z$ and resultant fieldfree perpendicular switching in a single ferromagnet without any spin torque generation layers, where ${\sigma }_z$ is achieved through the self-generated spin polarization in the ferromagnet that is engineered by the Néel order of an adjacent antiferromagnetic insulator. We further demonstrated that ${\sigma }_z$ emerges when the self-generated spin polarization is collinear with the Néel vector, where the spin current is reflected to the ferromagnet, along with rotated spin polarization toward the out-of-plane direction to induce ${\sigma }_z$. Since no current is shunted by the antiferromagnetic insulators and the Néel order does not rely on single-crystalline materials, these results may provide a CMOS-compatible solution for constructing energy-efficient fieldfree spintronic devices.

Multichannel coupling in hybrid systems makes an attractive testbed not only because of the distinct advantages entailed by each constituent mode but also because the opportunity to leverage interference among the various excitation pathways. Here, via combined analytical calculation and experiment, we demonstrate that the phase of the magnetization precession at the interface of a coupled yttrium iron garnet (YIG)/permalloy (Py) bilayer is collectively controlled by the microwave photon field torque and the interlayer exchange torque, manifesting a coherent, dual-channel excitation scheme that effectively tunes the magneto-optical spectrum. The different torque contributions vary with frequency, external bias field, and type of interlayer coupling between YIG and Py, which further results in destructive or constructive interferences between the two excitation channels, and hence selective suppression or amplification of the hybridized magnon modes.

Fluxoniums, as partially protected superconducting qubits, are promising to be employed in building high-performance large-scale quantum processor. The recently proposed “integer fluxonium” operates at zero external flux bias, with a frequency of approximately 3 GHz. Single-qubit gate fidelity has been demonstrated to exceed $99.9\mathrm{\%}$ [Mencia et al., PRX Quantum 5, 040318 (2024)], whereas two-qubit gate schemes and scalable architectures remain underexplored. In this work, we investigate a fluxonium-transmon-fluxonium (FTF) coupling architecture using integer fluxoniums. We first confirm suppression of $ZZ$ interaction in the FTF system and then propose two high-fidelity controlled-$Z$ (CZ) gate schemes utilizing the coupler control: a flux-activated adiabatic gate scheme and a microwave-activated nonadiabatic gate scheme. Both schemes are capable of achieving low coherent error of the order of $1\times {10}^{-6}$ within gate durations of several tens of nanoseconds. In addition, we discuss a hybrid circuit system in which an integer fluxonium is coupled to a conventional fluxonium through a transmon coupler. Our proposal provides insights for future implementations of large-scale quantum circuits based on integer fluxonium devices.

We present an acoustic leaky-wave antenna based on zero-refractive-index metamaterials, offering significantly enhanced radiation efficiency and directivity compared to conventional designs. The zero-refractive-index metamaterial incorporates periodically distributed space-coiling structures, leveraging Dirac-like dispersion and accidental degeneracy to achieve vanishing effective density and compressibility simultaneously. The proposed acoustic Dirac leaky-wave antenna (ADLWA) achieves more than double the radiation efficiency of conventional antennas utilizing arrays with shunt ducts and membranes. It also exhibits superior directional control, enabling precise beam scanning through frequency tuning. Additionally, the ADLWA functions as a passive sonar system capable of detecting the direction of arrival of moving sound sources. This work expands the possibilities for acoustic wave control, with potential applications in acoustic sensing and communication technology.

Accurately estimating the parameters that characterize physical processes plays a crucial role in revealing the essence of physical processes. Here, we demonstrate how to enhance the estimation precision of optomechanical coupling strength (OCS) through periodic modulation in a standard optomechanical system. In this study, we find that by properly designing the form of periodic modulation, the estimation precision of the OCS parameter can be enhanced significantly, and that the enhanced estimation precision is robust against dissipation channels. Using cavity optomechanics principles in practice, this work opens another avenue for improving quantum sensing by exploiting pump modulation.

Amplifying microwave signals with a noise level close to the minimum imposed by quantum mechanics is now routinely achieved with superconducting quantum devices. In particular, Josephson-based traveling-wave parametric amplifiers (JTWPAs) have shown record bandwidth with added noise close to the quantum limit [Macklin et al. Science 350, 307 (2015) and Planat et al. Phys. Rev. X 10, 021021 (2020)]. In this work, we report the appearance of echo signals emitted by JTWPAs driven by trains of high-power pulses near to or exceeding their dynamical range. These echoes have microsecond coherence, and we attribute their origin to microscopic defects in the amplifier’s dielectric layer. By analyzing the power and coherence of the echo signals as a function of temperature, we estimate the dielectric loss resulting from these defects and their impact on the quantum efficiency of the JTWPA. We introduce a mitigation technique (“BLAST”) to prevent the appearance of these echoes, which can alter measurements in experiments. This comprises an additional off-resonant high-power tone sent concurrently with each pulse. We demonstrate that this suppresses the spurious defect signals, and we recover the typical gain and noise figure within 95% of their low-power values in $300\mathrm{ns}$. These results can help to extend the use of JTWPAs in experiments where fast, high-power sequences are necessary to generate weak microwave responses from the system under study, and they also provide a path toward characterizing the dielectric losses of these devices in situ.

Identifying the origin of nonequilibrium characteristics in a generic interacting system having multiple degrees of freedom is a challenging task. In this context, information-theoretic measures such as mutual information and related polymorphs offer valuable insights. Here we explore these measures in a minimal experimental model consisting of two hydrodynamically coupled colloidal particles, where a nonequilibrium drive is introduced via an exponentially correlated noise acting on one of the particles. We show that the information-theoretic tools considered enable a systematic, data-driven dissection of information flow within the system. These measures allow us to identify the driving node and reconstruct the directional dependencies between particles. Notably, they help explain a recently observed, counterintuitive trend in the dependence of irreversibility on interaction strength under coarse-graining [Das et al., Phys. Rev. E 112, L023401 (2025)]. Finally, our results demonstrate how directional information measures can uncover the hidden structure of nonequilibrium dynamics and provide a framework for studying similar effects in more complex systems.

Current-induced spin torque is essential and crucial in spintronics. In this work, we systematically investigate the spin torque in transition metal (TM)/ferromagnet (FM) bilayers by using first-principles calculations and taking into account the phonon scattering at room temperature. To examine the spin and orbital Hall contributions, the studied transition metals include 5d heavy metals $\mathrm{Pt},\mathrm{W},\mathrm{Au},$ and $\mathrm{Ta}$ as well as 3d light metals $\mathrm{Ti},\mathrm{V},\mathrm{Cr},\mathrm{Cu},$ etc. We found that in TM$/\mathrm{Co}\mathrm{Fe}$ bilayers with typical 3d and 5d transition metals, the spin torque on $\mathrm{Co}\mathrm{Fe}$ mainly originates from the spin Hall mechanism, with the magnitude and sign of the damping-like torque efficiency consistent with those of the spin Hall conductivity (SHC). In TM$/\mathrm{Ni}$ bilayers, the spin torque is contributed by three mechanisms, including the spin and orbital Hall effect in the TM, as well as self-torque in $\mathrm{Ni}$. For TM$/\mathrm{Ni}$ bilayers, when SHCs are large in TMs, for instance in $\mathrm{W}$ and $\mathrm{Pt}$, the spin torques are mainly contributed by the spin Hall effect rather than the orbital Hall effect due to the partial cancellation of orbital and self-torque. For other cases, including $\mathrm{Ti}/\mathrm{Ni}$, $\mathrm{V}/\mathrm{Ni}$, and $\mathrm{Ta}/\mathrm{Ni}$, the orbital Hall torques also compete with either self-torque in $\mathrm{Ni}$ or the spin Hall effect in the TMs, which leads to the resultant spin torque efficiency not being pronounced. Our work reveals the less efficient contribution of the orbital Hall effect than the spin Hall effect on the spin torque in TM/FM bilayers.

Rock magnetic microscopy (RMM) has emerged as an advanced methodology for imaging the magnetization distribution of geological thin sections under ambient conditions, providing precise information with high spatial resolution and high magnetic field sensitivity; however, several factors—including the large size and complexity of sensors, their low magnetic field sensitivity and small field of view, and the need for cryogenic conditions—have impeded the widespread adoption of current RMM setups. Here, we present a room-temperature, fiber-coupling, scanning scheme for RMM based on the negatively charged nitrogen-vacancy (NV) centers in diamond. A $200\times 200\times 50\text{μ}{\mathrm{m}}^3$ diamond chip is glued to a multimode fiber ferrule for scanning imaging of the magnetic field. To ensure the precision of the magnetic field measurements, the diamond surface is coated with a reflective gold film. A spatial resolution of $180\text{μ}\mathrm{m}$ and a magnetic field sensitivity of $52\mathrm{nT}/{\mathrm{Hz}}^{1/2}$ in the near-dc frequency range below 10 Hz are achieved. This performance corresponds to a sensitivity of ${10}^{-12}\mathrm{A}{\mathrm{m}}^2/{\mathrm{Hz}}^{1/2}$ for magnetic moment measurements, approaching that of the superconducting rock magnetometer. The stray magnetic field distribution on a banded iron formation thin section is successfully scanned, revealing the inhomogeneous distribution of magnetization within the iron-rich bands. This study demonstrates the potential to extend the application scope of NV magnetometry in the frontiers of high-resolution geological research.

This work introduces and characterizes a theoretical model of a reflective polarimetric measurement technique determining the surface stress of a dielectric material, e.g., glass. We have developed a procedure to reconstruct the actual stress state from calculated Stokes vector components that would appear as polarization signals in a measurement. For the calculation, we consider a special geometry of the principal stress axis, where we chose the third principal axis corresponding to the z axis to be perpendicular to the surface and relaxed to a zero value. A created database represents the dependence of the reflected Stokes vector on the initial Stokes vector and the stress states included in the reflection matrix, which is iteratively calculated for several stress components and their orientations. The introduction of a model for the dependency of the reflected Stokes vector components on the stress states and the fitting of it to the database results in a system of equations of those dependencies that are solved for the stress state components and orientation. Finally, we found the theoretical determination accuracy of the model for surface stress magnitude to be on the order of a few megapascals and the orientation of the principal axes of stress can be determined with an accuracy of 20∘.

Ising machines efficiently solve binary optimization problems but face scalability limits in nonbinary tasks such as graph coloring due to their bistable dynamics. This work overcomes Ising machine scalability limits by introducing a Potts machine verified with novel experimental data from parametric three-state spins. We realize a three-state spin simulator using a nonlinear electronic oscillator built on the PFD3 (parametric frequency divider-by-three) process, demonstrating phase tristability with three equally probable states separated by 2π/3. Building on this, we construct a three-state Potts machine and determine its ground state using three coupled PFD3 oscillators. Our results show phase tristability onset at 0.76 dBm rf pump power, no dc power requirement, and over 8% conversion efficiency for one PFD3, paving the way for scalable Potts machines with more PFD3 surpassing Ising machines.