Superconducting cavities with high quality factors, coupled to a fixed-frequency transmon, provide a state-of-the-art platform for quantum information storage and manipulation. The commonly used selective number-dependent arbitrary phase (snap) gate faces significant challenges in ultrahigh-coherence cavities, where the weak dispersive shifts necessary for preserving high coherence typically result in prolonged gate times. Here, we propose a protocol to achieve high-fidelity snap gates that are orders of magnitude faster than the standard implementation, surpassing the speed limit set by the bare dispersive shift. We achieve this enhancement by dynamically amplifying the dispersive coupling via sideband interactions, followed by quantum optimal control on the Floquet-engineered system. We also present a unified perturbation theory that explains both the gate acceleration and the associated benign drive-induced decoherence, corroborated by Floquet-Markov simulations. These results pave the way for the experimental realization of high-fidelity, selective control of weakly coupled, high-coherence cavities, and expanding the scope of optimal control techniques to a broader class of Floquet quantum systems.

The accurate measurement of frequency is of great importance in many fields. One of the main limiting factors affecting the frequency stability of atomic clocks is laser noise. To achieve optimal frequency stability, it is essential to find an effective way to simultaneously eliminate laser noise effects. We propose a differential atomic clock using two atomic sensors whose laser noise is common-mode while the signal responses are opposite. We experimentally demonstrate this approach in two ${}^{87}\mathrm{Rb}$ atomic vapor cells. Compared with a conventional atomic clock using a single cell, the optical signal achieves an enhancement factor of 1.81, while the laser noise is reduced by approximately 20 dB, thus significantly improving the signal-to-noise ratio and short-term frequency stability of atomic clocks, with a frequency stability of $6.54\times {10}^{-13}/\sqrt{\tau }$ using the low-noise, well-operated laser. Notably, when subjected to deteriorated laser noise conditions, a 30-fold improvement in clock stability can be achieved. The results demonstrate that the current differential atomic clock is immune to laser noise. This protocol can be applied to a wide range of atomic clocks and interferometers that use the Ramsey method.

We present a minimal and general framework for initializing open quantum systems via gate operations, treating system-bath correlations and control dynamics on an equal footing. Our protocol simulates thermal equilibration followed by a gate pulse, modeled using a time-dependent Bloch-Redfield equation accurate to second order in coherence. After the gate, the system exhibits hybrid dynamics: populations evolve Markovianly, while coherences dephase as if the system were initially factorized. In fast, strongly dephasing regimes, initial system-bath correlations can revive coherence. Gate fidelities reveal spin-echo-like suppression of errors near $2\pi$ rotations, indicating an intrinsic mechanism for error cancellation. The approach is efficient and broadly applicable to both quantum devices and molecular complexes. Applications include fidelity optimization with respect to bath correlation times and coherence tracking in systems, such as the Fenna-Matthews-Olson complex. Our results show that long-lived excitonic coherences can arise from strongly non-Markovian dynamics triggered by ultrafast pulses.

Entanglement detection and characterization in multiqubit systems is a difficult and challenging problem in quantum information processing, and existing analytical methods are limited to small Hilbert space dimensions. We design and successfully implement artificial neural networks (ANNs) to detect and classify entanglement for three-qubit systems using limited state features. The overall design principle is a feed-forward neural network, with the output layer consisting of a single neuron for the detection of genuine multipartite entanglement (GME) and six neurons for the classification problem corresponding to six entanglement classes under stochastic local operations and classical communication (SLOCC). The models are trained and validated on a simulated dataset of randomly generated states. We achieve high accuracy, around 98%, for detecting GME as well as for SLOCC classification. Remarkably, the ANN concludes that it requires only seven diagonal elements of the entire density matrix to detect GME as well as to classify the state into one of the six entanglement classes with an accuracy greater than 94% for both these tasks. This is an intriguing result, which does not lend itself easily to an intuitive explanation. Reducing the size of the feature set makes it easier to apply ANN models for entanglement classification, particularly in resource-constrained environments, without sacrificing accuracy. The performance of the ANN models is further evaluated by introducing white noise into the dataset, and the results indicate that the models are robust and are able to tolerate noise well.

Triaxial spin-exchange-relaxation-free (SERF) atomic magnetometers (AMs), as opposed to the single-axis configuration, provide more comprehensive magnetic field information on biomagnetic measurements, effectively improving their capabilities for magnetic source reconstruction. Typically, the triaxial AM is considered to be three independent orthogonal single-axis AMs, but the interaction of the triaxial modulation is ignored. This study established a polarization-dynamics model under triaxial modulation, providing a theoretical model for triaxial AMs. On the basis of perturbation iteration theory, the modulation field along the cross-axis is regarded as a perturbation term. Subsequently, we established the polarization-dynamics model by summing the steady-state and multiorder perturbations of the triaxial polarization projections. Based on the proposed model, we discovered an optimal modulation coefficient formula for the triaxial SERF AM, replacing the constant optimal coefficient used when treating it as three independent single-axis AMs. The proposed optimal modulation coefficient exhibited a 12% improvement in response relative to the conventional coefficient. We also constructed a triaxial-modulation SERF AM to verify the proposed polarization-dynamics model under different triaxial-modulation parameters. The proposed polarization-dynamics model is beneficial for further investigation of triaxial SERF AMs and contributes to the improvement of their sensitivity.

We develop a local-heating scheme by drawing inspiration from spike-frequency adaptation (SFA) in neuroscience, which naturally fits the present probabilistic computing architecture. The SFA-based approach introduces negative feedback to the individual probabilistic bits (p-bits), effectively lowering the energy gradient in the Ising model and facilitating the system’s escape from local minima in complex energy landscapes. Using integer factorization of semiprime numbers ranging from 16 to 30 bits as a case study, we demonstrate that the SFA algorithm significantly enhances computational efficiency, with an acceleration that exceeds linear scaling with the bit number. We further illustrate the practicality of our SFA algorithm through circuit simulations using stochastic magnetic tunnel junction-based p-bits. This approach not only accelerates integer factorization but also holds promise for addressing other large-scale combinatorial optimization problems, thereby expanding the potential applications of probabilistic computing.

Topological disclination (TD) serves as an ideal platform for trapping localized zero-dimensional modes and has been extensively studied in classical wave systems. Due to the unconventional bulk-disclination correspondence in topological materials, TDs are robust against local lattice perturbations. However, most TD states lack chiral symmetry protection, which complicates the confinement of these modes near or at the midgap, particularly in photonic systems. In this work, we propose a confined Mie-resonance photonic lattice with rotational symmetries that supports an enlarged bandgap, and construct a two-dimensional metamaterial with a TD core that preserves chiral symmetry. This configuration ensures the confinement of degenerate TD states between the zero-energy line, preventing them from merging into bulk bands. Experimental results demonstrate that two pairs of degenerate TD modes are symmetrically located near the midgap. Our work provides a alternate perspective for realizing robust TD states in 2D photonic materials, releasing possibilities for the fabrication of topological optical devices.

Hafnia-based ferroelectric materials have enabled ferroelectric memory scaling to sub-20-nm nodes. Yet, the impact of nanopillar structures on ferroelectric switching dynamics remains unclear. In this work, we employ phase-field simulations to study domain evolution during and after switching in nanopillar capacitors. Our results reveal that the nanopillar geometry can cause depolarization behavior. A combination of thick domain walls, small pillar radius, and proper grain orientation should result in significant depolarization, characterized by a large maximum depolarization, a short depolarization time, and strong resistance to nonideal effects. This depolarization behavior is potentially beneficial for applications requiring high-permittivity dielectrics (such as next-generation DRAM), but needs to be suppressed for nonvolatile memory applications. We conclude by discussing the limitations and potential extensions of this work.

Scalable superconducting quantum processors require balancing critical constraints in coherence, control complexity, and spectral crowding. Fixed-frequency architectures suppress flux noise and simplify control via all-microwave operations but remain limited by residual $ZZ$ crosstalk. Here we propose a microwave-activated three-qubit gate protocol for fixed-frequency transmon qubits in the large-detuning regime ($|\mathrm{\Delta }|\gg g$), leveraging the third-order nonlinear interaction to coherently exchange $|001⟩\leftrightarrow |110⟩$ states. By incorporating a phase-compensated optimization protocol, numerical simulations demonstrate a high average gate fidelity exceeding $99.9\mathrm{\%}$. Systematic error analysis identifies static long-range $ZZ$ coupling as the dominant error source in multiqubit systems, which can be suppressed via operations in the large-detuning regime (approximately $1$ GHz). The protocol maintains process fidelities exceeding 98% under decoherence, while demonstrating intrinsic robustness to fabrication-induced parameter variations and compatibility with existing all-microwave two-qubit gate architectures. This hardware-efficient strategy advances scalable quantum computing systems by improving coherence properties, reducing spectral congestion, and expanding the experimental toolkit for error-resilient quantum operations in the noisy intermediate-scale quantum era.

Magnetic-annealing-induced uniaxial anisotropy is shown to influence vortex formation in magnetic tunnel junction (MTJ) free layers of various diameters, with micromagnetic simulations demonstrating a threshold for single-vortex formation that exhibits an inverse diameter dependence. Angular $M$-$H$ curves were measured for MTJ multilayers under different annealing conditions, and reveal that a two-step orthogonal magnetic annealing process reduces the uniaxial anisotropy in the free layer from $1040\mathrm{J}/{\mathrm{m}}^3$ to $130\mathrm{J}/{\mathrm{m}}^3$. This reduction in anisotropy allows for vortex formation in MTJ sensors as large as $40\text{μ}\mathrm{m}$. Increasing the MTJ diameter leads to an enhancement of magnetic sensitivity up to $2.80\mathrm{\%}/\mathrm{Oe}$ with the conventional definition, or $1.78\mathrm{\%}/\mathrm{Oe}$ via an ac sensitivity measurement that verifies the nonhysteretic response. This result demonstrates an eightfold increase in vortex-MTJ sensitivity, compared with standard MTJs that have diameters limited to 5 $\text{μ}\mathrm{m}$, and this work provides the foundation for highly sensitive vortex-MTJ-based sensors for applications that require a nonhysteretic, ultrasensitive response.

Quantum circuits for loading probability distributions into quantum states are essential subroutines in quantum algorithms used in physics, finance engineering, and machine learning. The ability to implement these with high accuracy in low-depth quantum circuits is a critical issue. We propose a quantum state-preparation method for probability distributions with reflection symmetry using matrix-product states. By considering reflection symmetry, our method reduces the entanglement of probability distributions and improves the accuracy of approximations by matrix-product states. As a result, we improve the accuracy by 2 orders of magnitude over existing methods. Our approach, which scales linearly with qubit count, is highly advantageous for noisy quantum devices. Our results also demonstrate that the approximation accuracy in tensor networks depends heavily on the bond dimension, with minimal reliance on the number of qubits. Our method is demonstrated for a normal distribution encoded into 10 and 20 qubits on a real quantum processor.

Obtaining a group velocity higher than the speed of sound in a waveguide is a challenging task in acoustic wave engineering. Even more challenging is to achieve this velocity increase without any intervention with the waveguide profile, such as narrowing or widening, and particularly without interfering with the passage by flexible inclusions, either passive or active. Here, we approach this problem by invoking concepts from non-Hermitian physics, and imposing them using active elements that are smoothly sealed within the waveguide wall. In a real-time feedback operation, the elements induce local pressure gain and loss, as well as nonlocal pressure integration couplings. We employ a dedicated balancing between the control parameters, derived from lattice theory and adjusted to the waveguide system, to drive the dynamics into a stable parity-time-symmetric regime. We demonstrate the accelerated propagation of a wave packet both numerically and experimentally in an air-filled waveguide and discuss the trade-off between stabilization and the achievable velocity increase. Our work prepares the ground for advanced forms of wave transmission in continuous media, enabled by short- and long-range active couplings, created via embedded real-time feedback control.

The localized absorption of radio frequency (rf) energy in biological tissue would benefit applications ranging from neuromodulation to cancer hyperthermia. Though previous works have made progress toward this goal, there remains an opportunity to experimentally demonstrate the ability to concentrate and focus rf energy deep within tissues or realistic tissue phantoms while minimizing background absorption in the surrounding medium. In this work, we present both theoretical and experimental demonstrations of “radioplasmonics,” the rf counterpart to optical plasmonics, enabling the manipulation of electromagnetic waves in the rf regime with similar principles. Specifically, we demonstrate that by tuning the dielectric functions and geometries of metamaterials with negative permittivity in the rf spectrum, we can achieve resonant absorption in specific biological tissues. We further provide heatmaps visualizing the resonance in dielectric space as a function of tissue type, applied frequency, and implant geometry. We also present the first known experimental demonstration of radioplasmonic heating in a biological tissue phantom, measuring strong resonant absorption of incident radio waves by rf metamaterials. To the best of our knowledge, this work includes the greatest differential-absorption ratio ever measured for an rf-absorbing material implanted deep within a tissue phantom.

Acoustic materials with Willis coupling have coupled constitutive equations, which lead to the cross-coupling between the monopole and dipole, analogous to the bianisotropic phenomena in electromagnetism. Though significant progress has been made in recent years in understanding Willis coupling, the extension of which to higher-order responses is still lacking. Here, an effective acoustic polarizability tensor is derived to understand the bianisotropic response of asymmetrical acoustic scatterers including the quadrupole couplings, in which the constraint of Helmholtz equation on the local field (pressure, velocity and the spatial derivatives of velocity) is utilized. Then, an experiment for the directivity enhancement of a point source near the asymmetrical acoustic scatterer is carried out, and a spatial Fano resonance phenomenon is observed.

Laser-induced ultrafast demagnetization dynamics of ${\mathrm{Tb}}_x({\mathrm{Dy}}_{0.2}{\mathrm{Co}}_{0.8}{)}_{1-x}$ ferrimagnetic alloy films with differing $\mathrm{Tb}$ compositions were systematically investigated by time-resolved magneto-optical Kerr effect measurements. In low-$\mathrm{Tb}$-doped compositions ($\mathrm{Co}$ rich), the one-stage demagnetization process is dominated by the spin-orbit coupling of the $\mathrm{Co}$ 3d spins. However, for high-$\mathrm{Tb}$-doped compositions ($\mathrm{Tb}$-$\mathrm{Dy}$ rich), a distinct discontinuous two-stage demagnetization emerges. Specifically, the second-stage demagnetization rate $1/{\tau }_2$ decreases monotonically with increasing x, and is dominated by intersublattice exchange coupling. A modified four-temperature model elucidates novel competing mechanisms underlying the demagnetization processes in ${\mathrm{Tb}}_x({\mathrm{Dy}}_{0.2}{\mathrm{Co}}_{0.8}{)}_{1-x}$ alloy thin films, and confirms the critical role of intersublattice exchange coupling in dominating the two-stage demagnetization process. These findings demonstrate that 3d-4f intersublattice coupling engineering—particularly through dual-rare-earth–single-transition-metal configurations—serves as a fundamental design paradigm for controlling ultrafast magnetic switching in rare-earth–transition-metal systems, providing new insights for developing next-generation high-speed spintronic memory devices.

We present a type of tunable magneto-optical metasurface performing Faraday rotation, the sign and value of which are not fixed after the structure fabrication but can be tuned in a wide range via heating of the metasurface. We demonstrate both experimentally and theoretically that the Faraday rotation angle is enhanced in the vicinity of the magnetodipole and electrodipole Mie resonances and can be changed in a wide range from $-{0.3}^{\circ }$ to $+{0.1}^{\circ }$ for the same metasurface at fixed wavelength of incident light under the temperature changes from 294 to 488 K. Such thermal heating can be performed by an external control laser. As laser radiation can be focused at the spots of approximately $1\text{μ}\mathrm{m}$ diameter, the magneto-optical response can also be tuned locally. Thus one may obtain the inhomogeneous magneto-optically induced polarization rotation distributions across the metasurface by the creation of the laser-beam patterns with the desired intensity profiles. Another possibility opened by the proposed metasurface is the self-modulation of polarization of laser light performed depending on its intensity.

We report a noncontact mechanism for directional injection of magnons in magnetic films when driven by a spin accumulation $\mu {\mu }_s$ of electrons of a nearby metallic layer, governed by the long-range dipolar coupling between magnons and electron spins, which spontaneously generates a magnon current ${\mathbf{J}}_m$ flowing in the film plane. Crucially, in such near-field radiative spin transfer, the magnon flow ${\mathbf{J}}_m$ is always perpendicular to the spin accumulation $\mu {\mu }_s$, showing a universal chiral-locking relation. The spin injection is efficient even when $\mu {\mu }_s$ is normal to the magnetization, a feature breaking the limitation of the spin transfer by contact exchange interaction. Our findings reveal the critical role of dipolar chirality in driving the magnon thermal current and paving the way for the functional design of magnonic devices based on near-field radiative spin transfer.

Skyrmions and skyrmionia are topological spin textures with considerable promise for magnetic memory applications and artificial intelligence applications. Except for their static properties, we present the generation and stabilization of dynamic skyrmions and skyrmionia in synthetic antiferromagnet based nanocontact spin-torque nano-oscillators. By increasing the current density, we observe various dynamic states, including the single dynamic droplet, single dynamic skyrmion, double dynamic skyrmions, dynamic SAF skyrmionia, and dynamic SAF skyrmions. These dynamic SAF skyrmions and skyrmionia exhibit pronounced breathing modes and high oscillation frequencies exceeding 10 GHz, even without external magnetic fields. Remarkably, their stability is maintained not by the Dzyaloshinskii-Moriya interaction, but by antiferromagnetic Ruderman-Kittel-Kasuya-Yosida coupling, dipolar interactions, and current-induced Oersted fields. This study demonstrates the existence of dynamic SAF skyrmions and skyrmionia in spin-torque nano-oscillators, paving the way for future innovations in high-frequency skyrmionic devices.