Ferrimagnets, composed of antiferromagnetically coupled magnetic sublattices whose net magnetization can be tuned by temperature, offer a unique platform for probing the symmetry of the spin currents they generate and for identifying the sublattice contributions to these currents. Here, we investigate the spin-current symmetries produced by a $\mathrm{Gd}\mathrm{Fe}\mathrm{Co}$ ferrimagnet at a fixed concentration and across a broad temperature range, including the magnetization-compensation point. Using complementary techniques based on spin-torque ferromagnetic resonance spectroscopy, we separate the contributions of the spin Hall effect (SHE) and the spin anomalous Hall effect (SAHE). We show that the torques arising from both mechanisms retain their sign across the magnetization-compensation temperature, and that the SAHE-driven damping-like torque has the opposite sign to the SHE-driven term. We suggest that both effects originate from distinct electronic subsystems: the SHE emerging from $\mathrm{Gd}$ $5d$ electrons, and the SAHE from $\mathrm{Fe}\mathrm{Co}$ $3d$ electrons. Consequently, the SHE sign remains insensitive to the magnetization state, whereas the SAHE sign does not invert at compensation, reproducing our observations. Together, these insights clarify the interplay between sublattices in ferrimagnetic spin transport and highlight the potential of ferrimagnetic spin currents to generate spin torques in adjacent layers or within the ferrimagnet itself.

Heterodyne interferometry for precision science often comes with an optical phase modulation, for example, for intersatellite clock noise transfer for gravitational-wave (GW) detectors in space, exemplified by the Laser Interferometer Space Antenna (LISA). The phase modulation potentially causes various noise couplings to the final phase extraction of heterodyne beatnotes by a phasemeter. In this paper, in the format of space-based GW detectors, we establish an analytical framework to systematically search for the coupling of various noises from the heterodyne and modulation frequency bands, which are relatively unexplored so far. In addition to the noise caused by the phase modulation, the high-frequency laser phase noise is also discussed in the same framework. The analytical result is also compared with a numerical experiment to confirm that our framework successfully captures the major noise couplings. We also demonstrate a use case of this study by taking the LISA-like parameters as an example, which enables us to derive requirements on the level of the laser and phase-modulation noises in the high-frequency regimes.

Piezoelectric phononic integrated circuits (PnICs), chip-scale platforms in which GHz frequency acoustic fields are routed in µm-scale waveguide geometries, have steadily advanced in performance and complexity, providing new degrees of freedom for manipulating microwave signals. Here, we consider the use of PnICs for implementing on-chip microwave interferometers ($f=3.4\mathrm{GHz}$) using a gallium nitride ($\mathrm{Ga}\mathrm{N}$) on silicon carbide ($\mathrm{Si}\mathrm{C}$) PnIC platform. We demonstrate controlled mode amplitude splitting, differential control (local phase shift), and mode recombination in an unbalanced ($\mathrm{\Delta }L=1.6\mathrm{mm}$) phononic Mach-Zehnder interferometer (MZI), achieving a maximum fringe visibility $>0.985$. The high visibility does not imply high sensitivity due to the presence of parasitic acoustic modes in the MZI. We quantify the effect of these parasitic guided modes in the interferometer, and discuss potential design improvements for achieving quasi-single-mode operation in PnICs, with a view toward enabling applications in microwave and acoustic signal processing and sensing.

We have designed, fabricated, and characterized microwave resonators made of granular-aluminum thin films with different oxygen content. The kinetic inductance fraction of these disordered superconductors was determined by electromagnetic finite-element simulations, conformal mapping techniques, and the frequency shift of the resonators with temperature. We compare these methods to assess model-dependent variations and to highlight their main limitations. This analysis aims to guide the community in choosing the most suitable method for designing kinetic inductance detectors, high -mpedance resonators, and superinductors. Additionally, we measured the internal quality factor as a function of microwave power at low temperature to characterize losses, which we identify as arising from two-level systems.

We theoretically propose a symmetric encryption scheme based on restricted Boltzmann machines that functions as a probabilistic Enigma device, encoding information in the marginal distributions of visible states while using bias permutations as cryptographic keys. Theoretical analysis demonstrates proven resistance against differential attacks through distribution-based encoding and computational complexity rooted in #P-hard partition function evaluation. Compatible with probabilistic computing hardware, the scheme establishes a physical-computational asymmetry where legitimate users can efficiently, the ciphertext, while adversaries face exponential-time complexity. Unlike conventional symmetric ciphers on digital computers that collapse immediately upon key exposure, this asymmetry preserves time-limited security even with fully exposed keys. This framework unlocks the potential of probabilistic computers for cryptographic systems, offering an emerging encryption paradigm between classical and quantum regimes for postquantum security.

We propose a neural-network-based model capable of learning the broad landscape of working regimes in quantum dot simulators and using this knowledge to autotune these devices—based on transport measurements—toward obtaining Majorana modes in the structure. The model is trained in an unsupervised manner on synthetic data in the form of conductance maps, using a physics-informed loss that incorporates key properties of Majorana zero modes. We show that, with appropriate training, a deep vision-transformer network can efficiently memorize the relations between Hamiltonian parameters and structures on conductance maps and use them to propose parameter updates for a quantum dot chain that drives the system toward a topological phase. Starting from a broad range of initial detunings in parameter space, a single update step is sufficient to generate nontrivial zero modes. Moreover, by enabling an iterative tuning procedure—where the system acquires updated conductance maps at each step—we demonstrate that the method can address a much larger region of the parameter space.

Transmission peak degeneracies (TPDs) have emerged as a promising alternative to exceptional points (EPs) for non-Hermitian sensing, providing square-root frequency splitting without the eigenbasis collapse and associated noise amplification that limit EP sensors. However, existing treatments of TPDs remain fragmented, lacking a unified theoretical framework, systematic figures of merit, or design principles for practical implementation. Here, we develop a comprehensive theory of two-dimensional TPDs that clarifies their relationship to EPs, maps their locations in parameter space, and provides analytic figures of merit for sensor design. We validate our theory using a tunable cavity-magnonics platform with in situ control of mode frequency, dissipation, and complex coupling via an effective synthetic gauge field. Our platform enables systematic exploration of six representative EP-TPD configurations spanning $\mathcal{P}\mathcal{T}$-symmetric, anti-$\mathcal{P}\mathcal{T}$-symmetric and anyonic-$\mathcal{P}\mathcal{T}$-symmetric regimes. Crucially, we show that TPDs, unlike EPs, can retain square-root splitting even under nuisance parameter drift through generalized transmission extrema degeneracies (TEDs). We further identify specific robust TPD configurations that minimize the impact of nuisance drift. These findings establish a unified theoretical and experimental framework for TPD-based non-Hermitian sensing.

Space-borne gravitational-wave detectors suppress overwhelming laser phase noise by recombining time-delayed heterodyne beatnote phases via time-delay interferometry (TDI). Simultaneously, TDI reshapes secondary noises in the phase, quantified through frequency-domain transfer functions. The dynamic orbits of the detectors modulate secondary noise by affecting arm-length variations, which couples into these transfer functions. We propose using a Fourier series to parameterize arm lengths. This yields an analytical method for calculating noise-transfer functions applicable to dynamic configurations for arbitrary TDI combinations. Using this method, we analyze three kinds of TDI combinations. For some TDI combinations, the secondary noise-transfer functions remain identical under both static equal-arm and dynamic triangular configuration assumptions. However, for zero-response combinations, the static equal-arm configuration assumption renders their secondary noise-transfer functions to zero. Thus, the transfer functions must be defined under dynamic triangular configuration conditions. For the $T[X,Y,Z]$ channel, the secondary noise-transfer function under the static equal-arm triangular configuration assumption is about 2 orders of magnitude lower than under dynamic triangular configuration assumptions. The proposed calculation method, being better aligned with realistic detector constellations, enables precise analytical expressions of secondary noise-transfer functions to be delivered for space-borne gravitational-wave detection data processing.

Superinductances are superconducting circuit elements that combine a large inductance with a low parasitic capacitance to ground, resulting in a characteristic impedance exceeding the resistance quantum $R_Q=h/(2e{)}^2\simeq 6.45\mathrm{k}\mathrm{\Omega }$. In recent years, these components have become key enablers for emerging quantum circuit architectures. However, achieving high characteristic impedance while maintaining scalability and fabrication robustness remains a major challenge. In this work, we present two fabrication techniques for realizing superinductances based on vertically stacked Josephson junctions. Using a multiangle Manhattan (MAM) process and a zero-angle (ZA) evaporation technique—in which junction stacks are connected pairwise using airbridges—we fabricate one-dimensional chains of stacks that act as high-impedance superconducting transmission lines. Two-tone microwave spectroscopy reveals the expected $\sqrt{n}$ scaling of the impedance with the number of junctions per stack. The chain fabricated using the ZA process, with nine junctions per stack, achieves a characteristic impedance of approximately $16\mathrm{k}\mathrm{\Omega }$, a total inductance of $5.9\text{μ}\mathrm{H}$, and a maximum frequency-dependent impedance of $50\mathrm{k}\mathrm{\Omega }$ at 1.4 GHz. Our results establish junction stacking as a scalable, robust, and flexible platform for next-generation quantum circuits requiring ultrahigh impedance environments.

Low-loss inductors are essential components in various superconducting circuits, such as qubits or digital electronics. In this study, we investigate highly compact inductors formed by vertically stacking Josephson junctions. Our implementation employs several layers of aluminum separated by tunnel barriers. Individual stacks are connected by suspended superconducting bridges, which are free of additional dielectric materials and, therefore, should not contribute significantly to losses. We present implementation details, fabrication results, and device characterization measurements.

Hardware-algorithm co-design provides an effective route for implementing quantum optimization on near-term hardware. Counterdiabatic (CD) protocols can accelerate adiabatic optimization but are difficult to realize digitally due to increased circuit depth and noise sensitivity. Here, we report a photonic co-design strategy that directly implements CD dynamics on a programmable photonic integrated circuit based on a Mach-Zehnder interferometer mesh. By exploiting the ability of the photonic processor to realize arbitrary unitary transformations, our approach bypasses gate-level decomposition and significantly reduces circuit depth. We further enhance the protocol by mitigating higher-order many-body terms in conventional CD optimization. An experimental demonstration of integer factorization achieves success probabilities up to 86% with only three layers, together with accelerated energy convergence, highlighting programmable photonic platforms for quantum optimization.

Two-level systems (TLSs) are a dominant decoherence mechanism in superconducting qubits, microwave kinetic inductance detectors, and quantum dots. TLSs are tunneling states commonly found in amorphous materials and interfaces, which interact electromechanically, leading to energy loss. Fluctuations in the frequency of the TLSs are a significant problem for qubit operation and force recalibration every few hours. In this study, we probe the effect of alternating bias at cryogenic temperatures on TLSs in a purpose-built LC oscillator. When an in situ alternating bias is applied, the steady-state spectra of the TLSs disappear. Spectroscopy reveals transient behavior, in which the TLS frequency fluctuates on the order of minutes. Thermal cycling above 10 K reverses these effects, restoring the TLS spectrum to its original state. Importantly, the intrinsic loss tangent of the LC oscillator remains unchanged before and after the application of the alternating bias. We propose that the disappearance of the steady-state spectrum is caused by nonequilibrium energy buildup from strain in the oxide film introduced by the pulsed voltage-bias sequence. Understanding this nonequilibrium energy could shed light on TLS fluctuations and reduce the calibration requirements for qubits.

Measurement-device-independent quantum key distribution (MDI-QKD) can be immune to all detector-side loopholes. Compared with weak-coherent-state sources, heralded single-photon sources (HSPSs) can effectively suppress vacuum components, and thus substantially improve the transmission distance and secure key rate of MDI-QKD. Here, we experimentally demonstrate an efficient MDI-QKD protocol based on HSPSs without vacuum sources [Phys. Rev. A 98, 032303 (2018)]. It achieves a secure key rate that is more than 60 times higher than the previous reported work at 10-dB transmission loss and extends the maximum transmission loss to more than 30 dB. These improvements are attributed to the efficient protocol used and the high-quality HSPSs prepared in the experiment, which enable a Hong-Ou-Mandel interference visibility of 95.1% at 10 mW. Furthermore, with improvements to experimental technology, the maximum transmission distance is expected to exceed 400 km. Therefore, the current work is expected to play a crucial role in the future development of large-scale quantum communication networks.

We develop a quantitative model of ionization processes in biological tissues under ultrahigh-dose-rate (UHDR) radiation. The underlying conjecture is that of electron-hole liquid (EHL) formation in water-based substances of biological tissues. Unlike the earlier known EHL in semiconductor crystals, the charge carriers here are poorly mobile, owing to strong interactions with the background (solvated electrons, etc.); hence, EHL resembling ionic melts is formed. Similar to all ionic systems, Coulomb coupling makes that EHL energetically favorable that leads to recombination barriers, suppressing subsequent structural transformations. In particular, the generation of secondary reactive species in such an EHL becomes limited, translating into a reduction of biological damage and tissue-sparing effects. We show how these processes are sensitive to the tissue quality and frequency dispersion of the dielectric permittivity. Equations for dose and dose rate defining the sparing thresholds are derived.

Spin-decoupled metasurfaces hold significant potential for integrated photonics by enabling independent manipulation of the spin degree of freedom of light. However, achieving robust spin-decoupled performance over both a broad bandwidth and a wide range of incident angles remains a pivotal challenge. In this work, a spin-decoupled strategy incorporating the propagation phase with the geometric phase is implemented to design plasmonic metasurfaces capable of independently controlling wave fronts of orthogonally circularly polarized light in the visible spectrum. Two representative devices demonstrate distinct spin-decoupled functionalities: one generating a vortex beam under left circular polarization (LCP) and the other enabling LCP-selective bifocusing, while both maintain specular reflection under right circular polarization. Systematic experimental characterization using microscopic spectroscopy demonstrates robust spin-decoupled performance across an 80 nm bandwidth and a wide range of incident angles with a scanning range of up to $40\text{μ}\mathrm{m}$. This dual advantage in spectral and angular stability, surpassing typical dielectric counterparts, provides solutions for reliable metasurface devices in applications such as multiplexed optical communications and miniaturized high-resolution imaging.

Compact models for two-dimensional field-effect transistors (2D FETs), predominantly adapted from conventional unipolar Si metal-oxide-semiconductor FET (MOSFET) frameworks, frequently fail to capture essential physics such as ambipolar conduction, threshold voltage roll-off, and output current upswing in saturation. While models based on Landauer formalism and the Pao-Sah approach offer partial solutions, their reliance on curve fitting and neglect of defects obscure the link to underlying device physics. Here, we introduce a physics-grounded carrier-phase-space (CPS) framework for 2D FET compact modeling. By employing the quasiequilibrium approximation and formulating the drain-source current as a path integral within the CPS, our model accurately describes threshold voltage roll-off, saturation current upswing, and ambipolar behavior. Crucially, analytical expressions for key electrical turning points across all operating regimes, including threshold voltage, saturation voltage, pinch-off voltage, and p-n-junction onset voltage, are derived for the first time through analysis of the bias-dependent integration path in CPS. Furthermore, the model incorporates the effects of ionized defects and is rigorously validated against experimental data from both ambipolar and unipolar FETs, demonstrating excellent electrostatic gating control and uniform thermal dissipation. This work establishes a comprehensive physics-based CPS compact model for 2D FETs, significantly advancing the foundation for their practical circuit design and manufacturing.

As one of the key frontiers of technological development in the modern world, rare-earth permanent magnets are now required to have a high maximum energy product and a Curie temperature, so as to meet the needs of today’s environmentally friendly technologies and applications. ${\mathrm{Sm}}_2{\mathrm{Fe}}_{17}{\mathrm{N}}_3$ is a promising rare-earth permanent magnet phase with a theoretical magnetic energy product of ≈59 MGOe, comparable with $\mathrm{Nd}$–$\mathrm{Fe}$–$\mathrm{B}$, and it contains no scarce heavy rare earths. The Curie temperature reaches 749 K and the corrosion resistance is excellent, making it suitable for high-temperature, high-stability applications. To understand magnetic properties and phase stability of ${\mathrm{Sm}}_2{\mathrm{Fe}}_{17}{\mathrm{N}}_3$ at high temperatures, we extracted a single-crystal nanoplate from powders and systematically investigated the evolution of the magnetic domains with temperature using advanced in-situ microscopy techniques and micromagnetic simulations. As the temperature increases from room temperature to 575 K, the nanoplates exhibit scalable mazelike magnetic domains, which is a reversible process driven by temperature-dependent magnetocrystalline anisotropy. When the temperature is further increased to 675 K, an irreversible domain evolution occurs, characterized by the formation of stripy magnetic domain walls and magnetic vortices. This phenomenon is associated with nitrogen escape from the lattice at the nanoscale due to its smaller activation energy (∼0.52 eV). The crystal structure remains stable until the temperature exceeds 675 K, at which point decomposition leads to the disappearance of the magnetic domains, indicating that the nitride nanomagnet exhibits promising thermal stability. This work advances the understanding of phase and magnetic stability in rare-earth nitrides, launching them as a promising platform for high-performance permanent magnetic applications.

We report on an experimental realization of multimaterial dielectric mirror coatings designed through a multi-objective optimization algorithm to simultaneously minimize thermal noise and optical losses. We validate this design strategy by fabricating and characterizing two distinct ternary systems: a ${\mathrm{Si}\mathrm{N}}_x$-based proof of concept and a ${\text{Ti::GeO}}_2$-based system targeting lower optical losses. The performance of the ${\mathrm{Si}\mathrm{N}}_x$ coating shows remarkable agreement with predictions, demonstrating a noise amplitude spectral density reduction of $0.82$ with respect to current reference coatings, and validating our design-to-fabrication pipeline. The ${\text{Ti::GeO}}_2$-based system achieves the crucial goal of sub-parts-per-million absorption; its measured thermal noise, however, is higher than the theoretically predicted level of $0.71$, extrapolated from single-layer material characterization. A dedicated tolerance analysis confirms that this discrepancy is not attributable to random thickness errors, emphasizing that further studies of the manufacturing process are needed to fully exploit this combination of materials. This work establishes a robust method for producing complex, high-performance optical coatings tailored for precision experiments.

The second-harmonic Hall technique is a widely used, sensitive method for studying the spin-orbit torques generated by charge current. It exploits the dependence of the Hall resistance on the magnetization direction, although thermal phenomena also contribute. Historically, deviations from the expected magnetic field dependence have usually been ignored. On the basis of our studies on permalloy/platinum bilayers, we show that a counterpart to the magnon-related spin-flip unidirectional magnetoresistance—known to appear in the second-harmonic longitudinal resistance—appears in the Hall data, and that describing the results in a wide field range with these contributions is essential to accurately estimate the torques.