CyberSec Research

A disordered quasi-liquid layer of water is thought to cover the ice surface, but many issues, such as its onset temperature, its thickness, or its actual relation to bulk liquid water have been a matter of unsettled controversy for more than a century. In this perspective article, current computer simulations and experimental results are discussed under the light of a suitable theoretical framework. It is found that using a combination of wetting physics, the theory of intermolecular forces, statistical mechanics and out of equilibrium physics a large number of conflicting results can be reconciled and collected into a consistent description of the ice surface. This helps understand the crucial role of surface properties in a range of important applications, from the enigmatic structure of snow crystals to the slipperiness of ice.

Photovoltaic conversion is highly dependent on the converter's temperature. In the absence of atmosphere, it can be rigorously determined using a thermal balance leading to a compact expression. The derivation starts from a fully spectral, two-sided radiative balance and proceeds to a practical gray-band (integrated) expression that can be used to estimate Tc from measurable quantities: plane-of-array irradiance, spectral absorptance (or a broadband absorptance), thermal emissivities, view factors to the regolith and to space, module electrical efficiency, and conduction to the mount. The model can be extended to other airless celestial bodies and to deep space.

Quantum random number generators (QRNGs) produce true random numbers, which are guaranteed by the fundamental principles of quantum physics. Miniaturization of QRNGs is crucial for a wide range of communication and cryptography applications. Here, we first report a fully functional QRNG chip based on vacuum-state fluctuations, with dimensions of 16.6 mm x 7.8 mm. The quantum entropy source, which is achieved via hybrid photonic integration with a SiO2 waveguide, generates raw quantum random numbers. The hybrid photonic and electrical components are assembled into a compact ceramic package using system-in-package technology. A microcontroller unit acquires the raw data and outputs the processed quantum random numbers via a serial peripheral interface. According to the characterization results, the QRNG chip achieves a constant real-time output rate of 5.2 Mbps across the industrial temperature range of -40{\deg}C to 85{\deg}C, making it suitable for practical applications.

Classical methods of sound absorption present fundamental limits that can be overcome by using nonlinear effects. Thin clamped plates have been identified as strongly nonlinear elements, capable of transferring the acoustic power of an incident air-borne wave towards higher frequencies. Here, we experimentally show that these plates exhibit different vibrational nonlinear behaviors depending on the amplitude and frequency of the excitation signal. The lowest excitation levels achieved lead to harmonic generation in a weakly nonlinear regime, while higher levels produce quasi-periodic and chaotic regimes. Since these nonlinear vibration regimes govern the acoustic frequency-up conversion process, we investigate the influence of relevant physical and geometrical parameters on the emergence of these nonlinear regimes. A parametric study on plates of different thicknesses reveals that the frequency-up conversion effect is mostly guided by the resonance of the plate at its first eigenfrequency, which depends not only on its thickness but also on a static tension introduced by the clamping. Finally, a design proposition involving multiple plates with different properties is presented in order to reach a broadband frequency-up conversion.

The exponential growth in satellite data traffic demands communication systems exceeding current microwave capacity limitations, while the terahertz (THz) frequency band (0.1-10 THz) offers unprecedented bandwidth potential with superior weather resilience compared to optical systems, particularly when combined with ultra-low Earth orbit (ULEO) satellite deployments below 300 km altitude. This article presents comprehensive channel modeling and performance evaluation for ULEO-THz satellite-to-ground communications, analyzing three distinct transmission architectures (direct satellite-to-ground, satellite-relay-ground forwarding, and satellite-to-high altitude base station with fiber backhaul) through altitude-resolved atmospheric propagation models validated using year-long meteorological data from four high-altitude stations in Tibet and Qinghai, China. The analysis incorporates frequency-dependent atmospheric absorption using ITU-R standards, free-space path loss with curved atmospheric modeling, and regional atmospheric variations to derive total channel path loss, available bandwidth capacity, and bit error rate (BER) performance under both AWGN and Weibull fading conditions across multiple THz frequencies. Results demonstrate that direct satellite-to-ground transmission at lower THz frequencies achieves optimal practical performance with maximum available bandwidth under QPSK modulation, while satellite-relay-ground forwarding suffers prohibitive cumulative losses from multiple hops, and satellite-to-high altitude base station configurations, despite favorable atmospheric channel characteristics, become impractical due to substantial electro-optical conversion penalties and fiber transmission losses in long-haul applications.

Heavy metal-free quantum-dot light-emitting devices (QD-LEDs) have demonstrated remarkable brightness, saturated color, and high efficiencies across a broad spectral range. However, in contrast to organic LEDs (OLEDs), QD-LED operational lifetimes remain limited, with the underlying degradation mechanisms not fully understood. In the present study, we show that InP/ZnSe/ZnS (red-emitting) and ZnTeSe/ZnSe/ZnS (blue-emitting) cadmium-free colloidal QD-LEDs undergo nanoscale morphological changes during operation. Specifically,interparticle coarsening and layer thinning are observed in the electron transport layer (ETL) consisting of ZnMgO nanoparticles (NPs), in the QD emissive layer, and in the organic hole transport layer. This is accompanied by the generation and diffusion of compositional oxygen- and hydrogen-radicals throughout the device, with oxygen accumulating at the electrode/ETL interfance. Moreover, in situ transmission electron microscopy reveals the electron beam exposure, in the presence of hydrogen radicals, accelerates ZnMgO NPs coarsening. To mitigate these degradation pathway, we show that acrylate-based resin-encapsulation treatment stabilize the ETL/QD layers by suppressing the radical formation and halting morphology changes. This approach achieves dramatic stability enhancements, exhibits an 8-fold and 5000-fold lifetime improvement on InP/ZnSe/ZnS and ZnTeSe/ZnSe/ZnS QD-LEDs, respectively. Our findings establish the causal relationships between the morphological degradation, interlayer radical dynamics, and state-of-the-art QD-LEDs instability, providing new insights into a scalable encapsulation treatment that enables efficient and long-lived Cd-free QD-LEDs.

Heat generated in gallium nitride (GaN) high-electron-mobility transistors (HEMTs) is often concentrated in nanoscale regions and must dissipate through multiple heterostructures. However, the influence of non-uniform heat sources on the thermal transport of such heterostructures remains unclear. In this work, a thermal transport model for heterostructures under the non-uniform heat source is developed by combining first-principles calculations with Monte Carlo simulations. Temperature, heat flux, and spectral thermal conductance distributions are compared between uniform and non-uniform heat sources. The effects of heterostructure height, heat source width, and heat source height on thermal transfer characteristics are analyzed for four typical heterostructures: GaN/AlN, GaN/Diamond, GaN/Si, and GaN/SiC. The results reveal that non-uniform heat sources have little effect on average interfacial thermal conductance but induce pronounced local non-uniformity when the heterostructure height is small. The interfacial thermal conductance near the heat source region is significantly higher than that in other areas. As the heat source non-uniformity increases, the total thermal resistance of the heterostructure rises markedly, reaching several times that under uniform heat sources. Finite-element calculations fail to capture the combined effects of non-uniform heating and microscale dimensions, leading to a severe underestimation of heterostructure total thermal resistance. This work reveals the thermal transport mechanisms of heterostructures under non-uniform heat sources and provides theoretical guidance for the thermal design of wide-bandgap semiconductor devices.

Phonon engineering technology has opened up the functional thermal management of semiconductor-based classical and quantum electronics at the micro- and nanoscales. However, challenges have remained in designing accurate thermal characteristics based on quasi-ballistic phonon transport. The quasi-ballistic thermal transport arises from the combination of wave-like and diffusive phonon behaviors unlike pure diffusion. The topological nature has been known to be compatible with both wave and diffusive phenomena. Therefore, topological phononic crystals have great potential for the development of controllable and designable thermal transport based on quasi-ballistic phonons. In this study, we experimentally investigated the thermal behavior at the scale of quasi-ballistic phonon transport using a 1D Su-Schrieffer-Heeger model-based topological phononic crystal. Quasi-ballistic phonon transport was observed through change in thermal conductivity depending on the structural parameters of topological systems using micro-thermoreflectance. Furthermore, using topological interface states, the experimentally observed thermal behaviors were found to agree well with the theoretically expected those. Accordingly, the topological nature is an effective approach for thermal management in micro- and nanoscale systems with quasi-ballistic phonon transport. Our results pave the way for a unified control scheme for wave and diffusion phenomena, such as quasi-ballistic phonons.

In this work, we demonstrate a high-performance surface acoustic wave (SAW) delay line based on a Scandium alloyed aluminum nitride (AlScN)-on-sapphire platform operating at 5.9 GHz with an exceptionally high acoustic propagation Q-factor. An 800 nm AlScN thin film with 40% scandium alloying concentration was deposited on a thick sapphire substrate to achieve strong acoustic energy confinement and large electromechanical coupling effect, thereby minimizing the insertion loss (IL) and propagation loss (PL) of the acoustic delay line (ADL). The proposed ADL was designed to operate in the Sezawa mode using a Single-Phase Unidirectional Transducer (SPUDT) electrode configuration for better unidirectionality. The fabricated ADLs with different delay lengths, after conjugate matching, exhibited delay times spanning 13 to 214 ns and IL ranging from 7.6 to 18.3 dB. The extracted PL reached as low as 9.2 dB/mm at 5.9 GHz, with a group velocity (v_g) of around 5,779 m/s. Based on these results, the proposed ADLs exhibit a high acoustic propagation Q-factor of 3,044. These findings highlight the potential of AlScN-on-sapphire platforms for high operational frequency, low-loss SAW ADL devices in advanced RF applications.

A simplified version of the semi-localized transitions (SLT) model is derived. The SLT-QE5 approximation reduces the number of differential equations from seven to five. Numerical calculations show that the approximation is very good for various trap parameters except the case with large reduction of activation energy during recombination to adjacent hole together with very low retrapping coefficient.

Understanding interstitial segregation in chemically complex alloys requires accounting for chemical and structural heterogeneity of interfaces, motivating approaches that move beyond scalar descriptors to capture the full spatial and compositional spectra of segregation behavior. Here, we introduce a spectral segregation framework that maps distributions of segregation energies for light interstitials in Ni as a function of local Cr coordination. Boron exhibits a broad, rugged energy spectrum with significant positional flexibility whereas carbon remains confined to a narrow spectrum with minimal displacement. At the free surface, Cr-rich coordination destabilizes both interstitials (e.g., positive segregation energies), in sharp contrast to the stabilizing role of Cr at the GB. This inversion establishes a natural segregation gradient that drives interstitials away from undercoordinated internal surfaces and toward GBs. These results underscore the limitations of single-valued segregation descriptors and demonstrate how a distributional approach reveals the mechanistic origins of interstitial--interface interactions in chemically heterogeneous alloys.

We demonstrate a grazing-incidence x-ray platform that simultaneously records time-resolved grazing-incidence small-angle x-ray scattering (GISAXS) and grazing-incidence x-ray diffraction (GID) from a femtosecond laser-irradiated gold film above the melting threshold, with picosecond resolution at an x-ray free-electron laser (XFEL). By tuning the x-ray incidence angle, the probe depth is set to tens of nanometers, enabling depth-selective sensitivity to near-surface dynamics. GISAXS resolves ultrafast changes in surface nanomorphology (correlation length, roughness), while GID quantifies subsurface lattice compression, grain orientation, melting, and recrystallization. The approach overcomes photon-flux limitations of synchrotron grazing-incidence geometries and provides stringent, time-resolved benchmarks for complex theoretical models of ultrafast laser-matter interaction and warm dense matter. Looking ahead, the same depth-selective methodology is well suited to inertial confinement fusion (ICF): it can visualize buried-interface perturbations and interfacial thermal resistance on micron to sub-micron scales that affect instability seeding and burn propagation.

This study investigates the feasibility of tilt-series neutron tomography for analyzing rhizoboxes used in root-soil interaction studies. Traditional neutron imaging methods are limited by constrained root growth volumes and poor penetration in moist soil. Using a vertical acquisition axis, the tilt-series approach avoids constraints typical of laminography. This method allows simultaneous radiographic and tomographic data acquisition, enhancing time resolution and providing detailed insights into root networks and soil water content. Experiments involved scanning six-week-old maize plants in rhizoboxes filled with sand. Results show that tilt-series tomography can effectively reconstruct root networks despite some artifacts from the missing wedge. While the tilt-series tomographic data qualitatively reveal water distribution changes, radiographic data remain essential for quantitative analysis. This approach demonstrates the potential for dynamic root-soil interaction studies, offering a valuable tool for agricultural and environmental research by providing comprehensive insights into the rhizosphere.

Error correction is essential for modern computing systems, enabling information to be processed accurately even in the presence of noise. Here, we demonstrate a new approach which exploits an error correcting phase that emerges in a system of three coupled nonlinear resonators. Within this phase, perturbed memory states are autonomously restored via the collective dynamics of the nonlinear network. We implement our scheme using a network of nanomechanical resonators. Nanomechanical systems are an attractive platform for low energy computing, but purely mechanical error correction has not been previously demonstrated. We experimentally show that the error correcting phase provides a 35 times reduction in the rate of errors, and allows robust error correction over a wide range of system parameters. These results highlight how emergent nonlinear dynamics can be harnessed for practical applications, paving the way towards error-resilient nanomechanical computing.

We introduce a transparent, encoding-agnostic framework for determining when the Capacitated Vehicle Routing Problem (CVRP) can achieve early quantum advantage. Our analysis shows this is unlikely on noisy intermediate scale quantum (NISQ) hardware even in best case scenarios that use the most qubit-efficient direct encodings. Closed-form resource counts, combined with recent device benchmarks, yield three decisive go/no-go figures of merit: the quantum feasibility point and the qubit- and gate-feasibility lines, which place any CVRP instance on a single decision diagram. Contrasting a direct QUBO mapping with a space-efficient higher-order (HOBO) encoding reveals a large gap. Applied to early-advantage benchmarks such as Golden-5, our diagram shows that HOBO circuits require only 7,685 qubits, whereas comparable QUBO encodings still exceed 200,000 qubits. In addition to identifying candidate instances for early quantum advantage in CVRP, the framework provides a unifying go/no-go metric that ingests any CVRP encoding together with any hardware profile and highlights when quantum devices could challenge classical heuristics. Quantum advantage in CVRP would likely require innovative problem decomposition techniques.

We report the development of a chromatic and spherical aberration corrector based on a combination of hexapole and quadrupole fields. Thick hexapole fields are used to generate negative spherical and to correct residual axial and off-axial aberrations. However, instead of using round transfer lenses placed between the hexapoles, a quadrupole multiplet producing superimposed electric and magnetic quadrupole fields is used to produce negative chromatic aberration. The quadrupole multiplet also functions as a transfer doublet within the corrector. In this paper, the simultaneous correction of chromatic and spherical aberrations using this corrector design is described and we demonstrate a resolution improvement in cases where the energy spread is limiting.

As quantum processors begin operating as tightly coupled accelerators inside high-performance computing (HPC) facilities, dependable and reproducible behavior becomes a gating requirement for scientific and industrial workloads. We present a hardware-maturity probe that quantifies a device's reliability by testing whether it can repeatedly reproduce the provably global optima of single-layer Quantum Approximate Optimization Algorithm (QAOA) circuits. Using harmonic analysis, we derive closed-form upper bounds on the number of stationary points in the p=1 QAOA cost landscape for broad classes of combinatorial-optimization problems. These bounds yield an exhaustive yet low-overhead grid-sampling scheme with analytically verifiable outcomes. The probe integrates reliability-engineering notions like run-to-failure statistics, confidence-interval estimation, and reproducibility testing into a single, application-centric benchmark. Our framework supplies a standardized dependability metric for hybrid quantum-HPC (QHPC) workflows.

Rydberg atoms, due to their large polarizabilities and strong transition dipole moments, have been utilized as sensitive electric field sensors. While their capability to detect modulated signals has been previously demonstrated, these studies have largely been limited to laboratory-generated signals tailored specifically for atomic detection. Here, we extend the practical applicability of Rydberg sensors by demonstrating the reception of real-world frequency-modulated (FM) audio transmissions using a consumer-grade handheld two-way radio operating in the UHF band. Detection is based on the AC Stark shift induced by the radio signal in a Rydberg atomic vapor, with demodulation performed using an offset local oscillator and lock-in amplification. We successfully demodulate speech signals and evaluate the audio spectral response and reception range. We show that all consumer-accessible radio channels can be simultaneously detected, and demonstrate simultaneous reception of two neighboring channels with at least 53 dB of isolation. This work underscores the potential of Rydberg atom-based receivers for practical, real-world FM signal detection.