Conventional optical materials are characterized by either a dissipative response, which results in polarization-independent absorption, or by a gain response that leads to wave amplification. In this work, we study a peculiar class of materials with chiral-gain properties, where gain selectively amplifies waves of one polarization handedness, while dissipation suppresses the opposite handedness. We uncover a novel phenomenon, “gain-momentum locking,” at the boundary of chiral-gain media, where surface plasmons are amplified or attenuated based on their direction of propagation. This effect, driven by the interplay between spin-momentum locking and polarization-sensitive non-Hermitian responses, enables precise control over unidirectional wave propagation. Our findings open the door to the design of unidirectional photonic devices with compensated attenuation and the generation of light with intrinsic orbital angular momentum.

With a growing interest in securing user data within the internet of things (IoT), embedded encryption has become of paramount importance, requiring light-weight high-quality random-number generators (RNGs). Emerging stochastic device technologies produce random numbers from stochastic physical processes at high quality; however, their generated random-number streams are adversely affected by process and supply-voltage variations, which can lead to bias in the generated streams. In this work, we present an adaptive variation-resilient RNG capable of extracting unbiased encryption-grade random-number streams from physically driven entropy sources, for embedded cryptography applications. The system’s key feature is its adaptive digitizer with an adaptive reference voltage. As a proof of concept, we employ a stochastic magnetic tunnel junction (sMTJ) device as an entropy source. The impact of variations in the sMTJ is mitigated by the adaptive digitizer, which generates an adaptive short-term average reference voltage that dynamically tracks any stochastic signal drift or deviation, leading to unbiased random bit stream generation. The generated bit streams, due to their higher entropy, then only need to undergo simplified postprocessing. A prototype of the adaptive RNG system was experimentally implemented using discrete electronic components and a field programmable gate array for entropy source emulation. Statistical randomness tests based on the National Institute of Standards and Technology (NIST) test suite are conducted on bit streams obtained using the simulations as well as the discrete electronic component implementation, demonstrating that the bit streams consistently pass all 16 tests of the NIST SP 800-22 test suite with a 100% pass rate. Leveraging its simplified postprocessing, the adaptive RNG shows consistent operation across a wide range of throughputs from 5 to 182 Mbps. Our results validate the system’s ability to generate encryption-grade random bit streams at reduced hardware cost for IoT devices.

Since the first proofs of concept in electromagnetics concerning the possibility of invisibilizing the presence of an inclusion in a field, a considerable amount of research has been carried out with the objective of generalizing these properties to other areas of physics. The case of waves in elastic solids is still an open problem, since it has been shown that traditional theory cannot be applied to this more complex type of wave propagation. We propose a design methodology still based on the geometrical transformation initially used, no longer with the aim of transforming the governing equation of Kirchhoff–Love plates, but with the aim of generating curved waveguides that force bending waves to propagate in the direction advocated by the preliminary idea of cloaking. Numerical results show that the resulting metamaterial is capable of making an inclusion invisible over a wide frequency band for a unidirectional incident wave. In addition to the numerical results, we provide results from experiments conducted on the manufactured cloak, confirming the relevance of the proposed design.

Interfacial engineering provides an effective route to tailor chiral magnetic interactions in thin-film heterostructures relevant for spintronic applications. In this work, we investigate the influence of top capping layers on perpendicular magnetic anisotropy (PMA) and interfacial Dzyaloshinskii-Moriya interaction (iDMI) in ultrathin Co films. By depositing Ru, Ta, W, and Pt on a 1.7 nm Co layer, we selectively modify the top interface while preserving the intrinsic growth of the ferromagnetic layer. Ferromagnetic resonance, Brillouin light scattering, vibrating sample magnetometry, and magneto-optical Kerr effect measurements are used to quantify the magnetic anisotropy and chiral exchange. We find that Ta capping yields a strong PMA, leading to perpendicular, spontaneously oriented magnetization and an iDMI of $-1.23\mathrm{pJ}/\mathrm{m}$, exceeding that obtained with W. In contrast, Ru and Pt capping layers lead to in-plane and canted magnetization spontaneously, respectively. The large PMA observed in Ta-capped films allows increased Co thickness while maintaining perpendicular anisotropy, which is expected to enhance spin polarization. These results demonstrate that top-interface engineering enables simultaneous tuning of magnetic anisotropy and iDMI, providing a practical pathway toward the design of magnetic tunnel junctions incorporating stabilized skyrmions.

Faster random telegraph noise (RTN) in magnetic tunnel junctions (MTJs) would be beneficial for probabilistic computing applications. However, the interactions between the macrospin and spin waves with finite wave numbers reduce the RTN attempt frequency. We theoretically show that mode-selective heating and cooling by parametric excitation of Kittel mode or propagating spin waves can substantially increase or decrease the RTN frequency, respectively, and propose a nonlinear cooling mechanism that accelerates the switching dynamics. We outline experimental pathways to characterize the nonlinear processes that maximize the operation speed of MTJ-based probabilistic (p-) bits.

The quantum sensing landscape has been revolutionized by advanced technologies like superconducting circuits and qubit-based systems, which have furthered the ability to probe and understand fundamental properties of quantum matter. Here, we propose an integrated photonic device where a transmon qubit capacitively couples to a microwave cross-resonator, and the setup is employed for sensing of time-reversal-broken order in materials. In this sensing scheme, the transmon qubit plays a dual role as both a control element and a passive detector, while the photonic cross-resonator serves as the host for the sample, enabling a contact-free spectroscopic method suitable for studying materials where reliable electrical contacts are challenging to obtain, e.g., in van der Waal 2D heterostructures. We show that by tuning the coupling strength and phase between the transmon and the cross-resonator, the system allows selective control over the interaction dynamics and leads to a highly sensitive detection method that can be compactly understood in terms of the evolution of excited state population and quantum metric of the resonator-transmon hybrid state. This architecture has the potential to host a wide range of quantum phenomena that can be precisely encoded in the dynamics of the transmon qubit and, in this way, potentially allows access to elusive aspects of correlated materials.

Attosecond and sub-attosecond pulses in the deep-ultraviolet (DUV), vacuum-ultraviolet (VUV), and soft-x-ray regimes provide direct access to electron dynamics in different electronic shells on their natural timescales. Despite rapid experimental progress, the temporal characterization of broadband VUV pulses and ultrabroadband soft-x-ray attosecond pulses remains a central and largely unresolved challenge. Here, we introduce a single-shot pulse-reconstruction framework that, for the first time, combines direct numerical solutions of the three-dimensional time-dependent Schrödinger equation (3D-TDSE) with data-driven optimization. By abandoning semi-analytical response models and instead employing full electron dynamics as the forward mapping, the reconstruction signal acquires substantially enhanced sensitivity to ultrabroadband waveforms, even in the presence of strong Coulomb and strong-field effects. We demonstrate accurate and noise-robust reconstructions of isolated attosecond pulses, attosecond pulse trains, and femtosecond-to-attosecond VUV pulses in regimes where conventional strong-field-approximation (SFA) or perturbative model-based approaches fail. Our work establishes a fundamentally different paradigm for attosecond pulse metrology, enabling reliable single-shot characterization across the VUV and soft-x-ray spectral regions.

Hydrodynamic cloak design aiming to suppress water flow disturbance by objects has become a popular research topic, with promising applications in drag reduction and stealth technology for marine engineering, bioengineering, and chemical engineering. Existing methods primarily utilize transformation optics theory (TOT) to derive analytical solutions for anisotropic viscosity tensors, which then inform the design process. However, they are limited to the Stokes equations, i.e., a simplified form derived from the full Navier-Stokes (NS) equations at Reynolds number (i.e., $\mathrm{Re}$) $\ll 1$, which neglects the important nonlinear flow convection term. In this study, we propose a framework based on the physics-informed neural network (PINN) to guide the design of hydrodynamic cloaks under the full NS equations, thereby enabling the characterization of effects across a wide range of Reynolds numbers. Within this framework, the PINN is employed to learn the anisotropic viscosity tensor necessary to achieve the design objective of enhancing upstream and downstream velocity field similarity, effectively weakening wake disturbance. Based on the learned anisotropic viscosity tensor, multiple candidate cloaks can be designed and evaluated. The optimal cloaks are then determined by implementing computational fluid dynamics (CFD) validation. Additionally, CFD results for the optimal cloaks demonstrate that the proposed method is effective for both two-dimensional (2D) and three-dimensional (3D) flows at $\mathrm{Re}=1$, 100, and 400, achieving up to a 64.46% reduction in the relative root mean square error of the downstream velocity profile compared to the upstream one. Furthermore, the analysis of the cloak mechanism using the $Q$-criterion reveals that the cloaked object generates an expanded zero-$Q$-criterion region, where the deformation of the fluid parcel compensates for its rigid-body rotation. As a result, flow disturbances around the object are effectively minimized.

Multivalued quantum encoding maps a classical alphabet of $M>2$ symbols onto multiple prescribed states. Here, we experimentally demonstrate multivalued quantum encoding in an effective two-level subspace of the electron spin of a nitrogen-vacancy center in diamond at room temperature. Classical symbols are mapped onto either the qubit population (polar angle $\theta$) or the coherence (azimuthal angle $\varphi$) via microwave pulses with controlled durations or phases. By coherently preparing four distinct states within the electron-spin qubit, we demonstrate image reconstruction symbol by symbol. No decoding errors are observed for the tested finite datasets under the reported repetition settings. To enhance robustness to channel noise, we further integrate an error-adaptive joint source-channel coding (EAJSCC) neural codec, which achieves a 2% compression ratio with a structural similarity index (SSIM) of 0.78, compared with SSIM approximately equal to $0.24$ for a conventional baseline. These results establish a viable route toward higher information density in room-temperature solid-state spin platforms.

Phase boundary, the interface between neighboring physical phases in matter, hosts various emergent phenomena and has been a pivotal subject of research interest for decades. Conventional techniques for the spatial resolution of phase boundaries rely on the interaction between the sample and certain probing particles, in which a pristine surface after stringent sample preparation and high vacuum are usually mandatory. Here we show that phase boundaries in metallic alloys can be resolved by lock-in thermography (LIT) in an ambient environment, even in the presence of a coating layer. An alternating charge current is applied through the sample, and the phase boundaries are revealed by the Peltier effect therein. We employ the LIT to visualize the propagation of phase boundaries in superelastic NiTi wires during the martensitic phase transition and demonstrate its capability to detect the martensite phase in a dental rotary file during mechanical bending. Furthermore, imaging of the phase boundaries in FeRh is successfully achieved using the same method, thereby demonstrating its broad applicability. This work offers a general technique for phase-boundary visualization in metallic materials, enabling versatile in situ nondestructive defectoscopy of phase-transition alloys in service.

Scalable quantum networks rely on optical links between long-lived qubits to distribute entanglement. Tin-vacancy (${\text{SnV}}^{-}$) centers in diamond combine long spin coherence at liquid-helium temperatures with highly coherent, spin-dependent optical transitions, making them promising network qubits. Connecting independent centers, however, requires indistinguishable photons: solid-state inhomogeneity creates frequency mismatch, while inversion symmetry suppresses the first-order electrical response. Here, we establish optical connectivity between two remote ${\text{SnV}}^{-}$ centers in separate cryogenic nodes. Using local electrodes, we tune the optical transition by up to 4 GHz via the Stark effect while maintaining optical coherence. Bringing the two transitions into resonance yields remote Hong-Ou-Mandel interference with a measured zero-delay visibility of $80(6)\%$ without postprocessing. The same electrodes provide dynamic spectral control, producing resolved Floquet sidebands at drive frequencies up to $1.5\mathrm{GHz}$. These results establish a locally reconfigurable optical interface for connecting remote ${\text{SnV}}^{-}$ quantum-network nodes.

High $1/f$ noise in Cryogenic CMOS (CryoCMOS) devices is a critical parameter to keep under control in the design of complex circuits for low-temperature applications. Current models predict the $1/f$ noise to scale linearly with temperature, and gate oxide defects are expected to freeze out at cryogenic temperatures. Nevertheless, it has been repeatedly observed that $1/f$ noise deviates from the predicted behavior and that gate oxide defects are still active around 4.2 K, producing random telegraph noise. In this paper, we probe single-gate oxide defects in 2500 nMOS devices down to 5 K in order to investigate the origin of $1/f$ noise in CryoCMOS devices. From our results, it is clear that the number of defects active at cryogenic temperatures resulting in random telegraph noise is larger than at 300 K. Threshold voltage shifts due to charged defects are shown to be exponentially distributed, with different modalities across temperatures and biases: from monomodal at 300 K to trimodal below 100 K. Distributions’ shapes are interpreted in the framework of percolation theory. By fitting these distributions, it is shown that more than 80% of the detected defects belong to the bulk oxide. Afterward, starting from the raw data in the time domain, we reconstruct the low-frequency noise spectra, highlighting the contributions of defects belonging to different branches and, therefore, to different oxide layers. This analysis shows that, although interface traps and large defects associated with the third mode are the main sources of $1/f$ noise at 5 K, bulk oxide defects still contribute significantly to low-frequency noise at cryogenic temperatures. Finally, we show that defect time constants and step heights are uncorrelated, proving that the elastic tunneling model for charge trapping is not accurate.

We investigate the coherence properties of parity-protected $\cos (2\phi )$ qubits based on interference between two Josephson elements in a superconducting loop. We show that qubit implementations of a $\cos (2\phi )$ potential using a single loop, such as those employing semiconducting junctions, rhombus circuits, Flowermon, and KITE structures, can be described by the same Hamiltonian as two multiharmonic Josephson junctions in a SQUID geometry. We find that despite the parity protection arising from the suppression of single Cooper-pair tunneling, there exists a fundamental trade-off between charge and flux-noise dephasing channels. Using numerical simulations, we examine how relaxation and dephasing rates depend on external flux and circuit parameters, and we identify the best compromise for maximum coherence. With currently existing circuit parameters, the qubit lifetime $T_1$ can exceed milliseconds, while the dephasing time $T_{\phi }$ remains limited to only a few microseconds due to either flux or charge noise. Our findings establish practical limits on the coherence of this class of qubits and raise questions about the long-term potential of this approach.

Under strong drives, which are becoming necessary for fast high-fidelity operations, transmons can undergo drive-induced state transitions. These transitions can involve dressed states of the driven transmon, which are chaotic. Whenever the computational manifold containing the transmon ground and excited states couples to such states, enhanced offset-charge sensitivity and destructive effects in readout can appear. We show here that these detrimental effects can further propagate to other degrees of freedom, for example to neighboring qubits in a multiqubit system. Specifically, we show that a coherently driven transmon can act as a source of incoherent noise to another circuit element coupled to it. By using a full quantum model and a semiclassical analysis, we perform the noise spectroscopy of the driven transmon by considering its coupling to a two-level system (TLS), and we show that, in a certain limit, the interaction with the driven transmon can be modeled as a stochastic diffusive process driving the TLS.

Broadband achromatic acoustic focusing remains challenging because most metalenses provide only single frequency phase compensation and lack the approximately constant group delay that is required to suppress focal drift. Here, we show that achromatic focusing can be achieved when the unwrapped transmitted phase of each unit cell in the metalens varies linearly with frequency. Based on this criterion, we design a compact acoustic metalens with deep subwavelength side-branch cavity units. An analytical model is developed to describe the broadband transmission characteristics of the proposed units and to enable predictable linear phase control. Within the investigated parameter space, all unit cells exhibit inherently linear phase responses with tunable phase slopes and frequency-dependent transmission amplitudes. Leveraging these blocks, we realize achromatic focusing by mapping the required phase profile at each frequency onto the corresponding unit cells. Finite element simulations demonstrate a nearly stationary focal length over the frequency range from 3 to 8 kHz. Experimental measurements reproduce the main broadband focusing tendency, although larger deviations are observed at low frequency. These results support the proposed design criterion for broadband achromatic acoustic focusing. The adaptability of the analytical framework is further demonstrated through the design of a second metalens with a different focal length.

Mirror symmetry of transmission is generally considered an inherent property of reciprocal systems. Metagratings, governed by the acoustic diffraction laws in a periodic lattice, have brought vitality to classical wave physics and its manipulation. However, even using the diffraction ability of waves, it remains a challenge to break the mirror symmetry of wave transmission through a single passive metagrating, while simultaneously controlling the wavefront in acoustics. Here, we propose a widely applicable description of acoustic wave diffraction in metagratings by incorporating the coupling between transmitted and reflected waves. Through deliberate design of the transmission and reflection phase gradients, we construct a monolayer passive phase-gradient metagrating that offers advantages of structural integrity and ease of fabrication. This design enables the breaking of mirror symmetry in both acoustic plane wave transmission and reflection within a reciprocal system. We further demonstrate its applicability across a broad range of incident angles, facilitating versatile wavefront manipulation. Our work provides a pathway to advance acoustic communication and isolation, and the underlying principle can be extended to other classical wave systems.

We investigate the post-threshold emission characteristics of supersymmetric (SUSY) semiconductor laser arrays beyond the linear regime. In contrast to previous studies based primarily on linear analyses or simplified nonlinear descriptions, we employ a realistic class-B semiconductor laser model incorporating the full field-carrier rate equations. Using two representative SUSY laser configurations, we examine the stability of steady-state operation and the emergence of in-phase synchronization in the nonlinear regime. Our results show that the inclusion of a SUSY partner can significantly reshape the steady-state stability landscape and, in certain parameter regimes, promote single-mode operation in the fundamental in-phase supermode. However, we demonstrate that linear suppression of higher-order supermodes does not generically ensure robust single-mode emission once gain saturation, modal competition, and amplitude-phase coupling are taken into account. These findings establish that the operational performance of SUSY laser arrays cannot be inferred from linear spectral arguments alone. Instead, the interplay among coupling strength, dissipation, pump level, and carrier dynamics fundamentally restructures the nonlinear stability diagram. Our work underscores the necessity of comprehensive nonlinear modeling for the design and optimization of SUSY-based laser arrays aimed at achieving stable coherent emission. Beyond laser physics, our results may offer broader guidance for tailoring and engineering synchronization characteristics in other platforms, including mechanical and electronic systems.