Papers

This paper describes the development of a generalized, physics-based theoretical model for estimating Rossiter modes for flow over rectangular cavities for regimes ranging from subsonic to hypersonic without requiring a priori knowledge of the detailed cavity-flow dynamics. This model addresses the issues with the Heller Bliss model, which despite incorporating compressibility effects, shows increasing deviations from experimentally measured Rossiter modes above Mach 3. The proposed model exploits the fact that the acoustic propagation speed governing the Rossiter feedback mechanism depends on the excitation and relaxation of internal energy modes. To account for these effects, an effective temperature is constructed from estimated post-shock conditions and used to evaluate an effective speed of sound, which is then used in the Rossiter relation to calculate the Strouhal number. The Strouhal numbers predicted by the model are compared with available experimental and high-resolution two-dimensional numerical simulations (conducted as a part of this study) from Mach 2 to Mach 9; our results agree very well with these datasets, thus supporting the conclusion that thermodynamic energy-mode participation and relaxation can alter the acoustic feedback timescale governing cavity oscillations. The formulation therefore provides a physics-based estimate of Rossiter-mode frequencies without requiring prior CFD or experimental characterization of the detailed cavity-flow dynamics.

The move to next-generation wireless communications with extremely large-scale antenna arrays (ELAAs) brings the communications into the radiative near-field (RNF) region, where distance-aware focusing is feasible. However, high-frequency RNF links are highly vulnerable to blockage in indoor environments dominated by half-space obstacles (walls, corners) that create knife-edge shadows. Conventional near-field focused beams offer high gain in line-of-sight (LoS) scenarios but suffer from severe energy truncation and effective-rank collapse in shadowed regions, often necessitating the deployment of auxiliary hardware such as Reconfigurable Intelligent Surfaces (RIS) to restore connectivity. We propose a beamforming strategy that exploits the auto-bending property of Airy beams to mitigate half-space blockage without additional hardware. The Airy beam is designed to “ride” the diffraction edge, accelerating its main lobe into the shadow to restore connectivity. Our contributions are threefold: (i) a Green's function-based RNF multi-user channel model that analytically reveals singular-value collapse behind knife-edge obstacles; (ii) an Airy analog beamforming scheme that optimizes the bending trajectory to recover the effective channel rank; and (iii) an Airy null-steering method that aligns oscillatory nulls with bright-region users to suppress interference in mixed shadow/bright scenarios. Simulations show that the proposed edge-riding Airy strategy achieves a Signal-to-Noise Ratio (SNR) improvement of over 20 dB and restores full-rank connectivity in shadowed links compared to conventional RNF focusing, virtually eliminating outage in geometric shadows and increasing multi-user spectral efficiency by approximately 35% under typical indoor ELAA configurations. These results demonstrate robust RNF multi-user access in half-space blockage scenarios without relying on RIS.

We propose an inverse-squeezing Kennedy receiver for discriminating binary phase-shift-keyed displaced squeezed vacuum states. The receiver combines a Kennedy-type nulling displacement, an orthogonally oriented inverse-squeezing operation and photon-number-resolving detection with a maximum-a-posteriori threshold rule. Its key mechanism is that the inverse-squeezing stage converts transmitter-side squeezing into enhanced photon-number contrast, or equivalently an effective coherent-state energy gain, that can be directly exploited at the measurement stage. Under ideal equal-prior conditions, the receiver surpasses the standard quantum limit for squeezed-state binary phase-shift keying at approximately $N\approx 0.3$, outperforms the Helstrom bound of coherent-state binary phase-shift keying at approximately $N\approx 0.4$, and reaches the 1% error level near $N\approx 0.6$. We further analyze its performance under realistic imperfections, including finite detector efficiency, dark counts, channel phase diffusion, receiver thermal noise and transmission loss. The results show that adaptive thresholding preserves robust performance against detector and noise imperfections over practical parameter ranges, whereas transmission loss progressively suppresses the squeezing-enabled advantage. These findings indicate that, for the fixed source parametrization adopted in this work, the proposed receiver is most advantageous in the low-loss regime, especially at low source energies.

Accurate monitoring of temperature, axial strain, and refractive index is critical for structural health monitoring, industrial process control, and environmental sensing. However, conventional optical fiber sensors are often limited by strong parameter cross sensitivity, poor discrimination capability, and increased system complexity when multiple sensing units are required. In this work, a compact multi-parameter optical fiber sensing platform is proposed based on a cascaded single-mode fiber, multimode fiber, and long-period fiber grating structure, combined with a wavelength-based spectral demodulation strategy. Within the cascaded configuration, multiple characteristic spectral troughs arising from distinct physical mechanisms coexist in a single transmission spectrum. Interference-induced troughs are generated by the multimode fiber section, while a resonance-induced trough is introduced by the long-period fiber grating. Although none of these troughs responds exclusively to a single parameter, each exhibits simultaneous and linearly independent responses to temperature, axial strain, and refractive index with distinct sensitivity magnitudes and trends. Consequently, each trough can be described by a unique sensitivity vector, enabling robust multi-parameter discrimination through multi-wavelength spectral demodulation.

High-frequency instabilities in crossed-field ($\bm E\times\bm B$) plasmas are widely implicated in anomalous cross-field electron transport in Hall thrusters and related devices. Building on the fully kinetic 3D electrostatic dispersion relations reported by Ducrocq et al. and later by Lafleur et al., we provide a concise, self-contained derivation of the key missing step: the magnetized-electron density perturbation $n_{e1}$ obtained from the linearized Vlasov equation via a retarded integration along unperturbed orbits, including finite-Larmor-radius effects and cyclotron harmonics. We collect the required mathematical identities in appendices and clarify the mapping between the Ducrocq Poisson-form and the Lafleur dielectric-form representations, including ion closures (cold-fluid versus kinetic Landau response). We conclude with a brief discussion of the assumptions and possible extensions toward more realistic configurations.

The evolution of modal crosstalk in multimode fibers is investigated using four different experimental and numerical approaches. Results converge to demonstrate that the fiber disorder alone is capable of generating steady states characterized by non-uniform modal power distributions, which promote the lower-order modes at the expenses of the higher-order ones and are properly described by a weighted Bose-Einstein law.

Purpose: This essay is a retelling of general relativity in a language in which space-time geometry is expressed as a fluid. This trivial and useful reformulation gives 1) a non-perturbative covariant description of cosmological inhomogeneities and 2) a simple formula describing how cosmic inhomogeneities are generated on super-horizon scales. Methods: Equating the Ricci curvature with the associated matter stress-energy gives a description of space-time geometry in terms of fluid properties. These locally measurable (covariant) non-perturbative quantities are in some ways superior to commonly used "gauge invariant" quantities. The dynamics of a quantity (kurvature) which describes cosmological inhomogeneities is described in detail. A detailed comparison is made of space-time fluid dynamics with that of a classical (Newtonian physics) fluid. Results: The fluid lexicon permits an unambiguous definition of the velocity of space-time. The evolution of the space-time fluid is in many ways identical with that of the classical fluid when expressed in Lagrangian coordinates. Kurvature is a measure of the specific binding energy of the fluid and is a most useful covariant measure of cosmological inhomogeneities. For plausible matter models kurvature will increase, even on super-horizon scales, due to non-linear hydrodynamic effects rather than gravity. This phenomena is also exhibited by classical fluids. Conclusion: The space-time fluid representation of geometrodynamics gives a simple and useful description of the evolution of cosmological inhomogeneities.

We, as researchers in quantum science and technology, are publishing this manifesto to express our deep concerns about the current geopolitical situation and the global race to rearm. We firmly oppose all forms of militarization in our societies and, in particular, within the academic world. We categorically reject the use of our research for military applications, population control, or surveillance. We stand against the practice of military funding for research. This manifesto is a call to action: to confront the elephant in the room of quantum research, and to unite all researchers who share our views. Our main goals are: i) To express, as a unified collective, our rejection of the use of our research for military purposes; ii) To open a debate in our community about the ethical implications of quantum research for military purposes; iii) To create a forum where concerned scientists can share their opinions and join forces in support of demilitarized research; iv) To advocate for the establishment of a public database listing all research projects at public universities funded by military or defense agencies. In what follows, we lay out our concerns and the rationale behind our opposition to the militarization of quantum research.

The shale revolution, driven by advances in horizontal drilling, multi-stage hydraulic fracturing, and cyclic gas injection, has reshaped the oil and gas industry over the past two decades. In the United States, these technologies transformed ultra-low permeability shale formations into commercially viable resources, increasing crude oil production from 5 million bpd in 2008 to more than 12 million by 2019. Horizontal drilling became the standard after 2010, with nearly 200,000 horizontal wells completed by the end of 2023, accounting for more than 80% of all new wells in the US. This success is now being replicated in Argentina making the country a leading unconventional producer. The common driver in both cases is the mass manufacturing approach, which industrializes oil production through standardized well designs, repeatable workflows, multi-well pad drilling, and continuous process optimization. Supported by a competitive oilfield service market and a skilled technical workforce, this model has reduced drilling times from months to weeks and cut well costs by half over the past decade. New technologies such as precision geosteering, advanced completion designs, real-time drilling analytics, and cyclic gas injection continue to improve efficiency and productivity. Applying these methods and technologies to conventional reservoirs could significantly expand global production capacity and place sustained downward pressure on crude oil prices. This paper argues that in a period of slowing economic growth and potential financial deleveraging, abundant supply from both unconventional and conventional developments could extend a prolonged phase of relatively low oil prices. Such a scenario would have far-reaching implications for energy policy, investment strategies, and the competitive position of oil-producing nations.

Digital cameras and displays utilise picture elements (pixels) that perform a single function: detecting or emitting light intensity. To exploit the full information content of electromagnetic waves, more advanced elements are required. This has driven the development of multifunctional components, which for example, simultaneously detect and emit intensity or extract intensity and spectral information. However, no pixel exists that both senses and generates optical wavefronts with full control over amplitude, phase, and polarisation, limiting reciprocal control and feedback of sophisticated light fields. Here we present a route to such pixels by demonstrating a versatile platform of miniaturised diffractive elements based on Fourier optics. We exploit plasmonic surface waves, which propagate coherently and efficiently across metallic surfaces. When these plasmons are launched towards wavy microstructures designed with simple Fourier analysis, arbitrary and background-free optical wavefronts are generated. Conversely, incoming light can be sensed and its amplitude, phase, and polarisation fully characterised. By combining or superposing several such components, we create multifunctional 'Fourier pixels' that provide compact and accurate control over the optical field. Our approach, which could also use photonic waveguide modes, establishes a scalable, universal architecture for vectorially programmable pixels with applications in adaptive optics, holographic displays, optical communication, and quantum-information processing.

The Casimir interaction in salted water contains a universal contribution of electromagnetic fluctuations that makes it of a longer range than previously thought. The universal contribution dominates non universal ones at the distances relevant for actin fibers inside the cell. We discuss universal and non-universal contributions with a model mimicking biological matter. We also show that the universal Casimir effect should have important implications at the cell scale.

Molecular simulations of interfacial polar media routinely employ periodic boundary conditions parallel to the interface. We show that this lateral periodicity introduces a spatially uniform in-plane mode ($q_{\parallel}=0$) that is unscreened because every lateral replica carries identical charge fluctuations. This 2D mode reduces the plane-averaged potential to a stochastic integral of the plane-averaged charge density along $z$, so that in a semi-infinite slab the variance of the potential grows linearly with depth. In a finite or periodic cell along $z$, with boundaries held at fixed potential, it follows a parabolic profile–a Brownian bridge–pinned to zero at both ends, with amplitude inversely proportional to the lateral cell area. These diverging fluctuations are a pure artifact of the imposed 2D lateral periodicity: they remain bounded in systems that are non-periodic or of finite lateral extent. We provide an analytic expression for their magnitude in dipolar media, yielding a practical criterion for the choice of lateral cell dimensions.

We aim to investigate the impact of image and signal properties on visual attention mechanisms during a signal detection task in digital images. The application of insight yielded from this work spans many areas of digital imaging where signal or pattern recognition is involved in complex heterogenous background. We used simulated tomographic breast images as the platform to investigate this question. While radiologists are highly effective at analyzing medical images to detect and diagnose diseases, misdiagnosis still occurs. We selected digital breast tomosynthesis (DBT) images as a sample medical images with different breast densities and structures using digital breast phantoms (Bakic and XCAT). Two types of lesions (with distinct spatial frequency properties) were randomly inserted in the phantoms during projections to generate abnormal cases. Six human observers participated in observer study designed for a locating and detection of an 3-mm sphere lesion and 6-mm spicule lesion in reconstructed in-plane DBT slices. We collected eye-gaze data to estimate gaze metrics and to examine differences in visual attention mechanisms. We found that detection performance in complex visual environments is strongly constrained by later perceptual stages, with decision failures accounting for the largest proportion of errors. Signal detectability is jointly influenced by both target morphology and background complexity, revealing a critical interaction between local signal features and global anatomical noise. Increased fixation duration on spiculated lesions suggests that visual attention is differentially engaged depending on background and signal spatial frequency dependencies.

Ultra-High Field MRI (UHF-MRI) is increasingly used in large-scale neuroimaging studies, yet automatic brain segmentation and cortical parcellation remain challenging due to signal inhomogeneities, heterogeneous contrasts and resolutions, and the limited availability of tools optimized for UHF data. Standard software packages such as FastSurferVINN and SynthSeg+ often yield suboptimal results when applied directly to UHF images, thereby restricting region-based quantitative analyses. To address this need, we introduce GOUHFI 2.0, an updated implementation of GOUHFI that incorporates increased training data variability and additional functionalities, including cortical parcellation and volumetry. GOUHFI 2.0 preserves the contrast- and resolution-agnostic design of the original toolbox while introducing two independently trained 3D U-Net segmentation tasks. The first performs whole-brain segmentation into 35 labels across contrasts, resolutions, field strengths and populations, using a domain-randomization strategy and a training dataset of 238 subjects. Using the same training data, the second network performs cortical parcellation into 62 labels following the Desikan-Killiany-Tourville (DKT) protocol. Across multiple datasets, GOUHFI 2.0 demonstrated improved segmentation accuracy relative to the original toolbox, particularly in heterogeneous cohorts, and produced reliable cortical parcellations. In addition, the integrated volumetry pipeline yielded results consistent with standard volumetric workflows. Overall, GOUHFI 2.0 provides a comprehensive solution for brain segmentation, parcellation and volumetry across field strengths, and constitutes the first deep-learning toolbox enabling robust cortical parcellation at UHF-MRI.

We present a theoretical study of spin-wave scattering by a twisted domain wall (DW) in a two-dimensional ferromagnet with easy-axis anisotropy. While the twisted DW generates an effective gauge field for spin waves, leading to a deflection of their trajectories, our main focus is on a distinct effect that arises when a hard-axis anisotropy is present in addition to the easy-axis anisotropy. In this case, the translational symmetry of the spin-wave Hamiltonian along the DW is broken, resulting in a periodic modulation of the Hamiltonian. This periodicity leads to the formation of multiple diffracted spin wave modes on both sides of the DW, engendering a DW-induced magnonic diffraction pattern. The interplay between the emergent gauge field and the anisotropy-induced periodicity reveals rich spin-wave dynamics and suggests potential applications for manipulating magnon flow in two-dimensional magnetic textures.

We observe the emergence of a distinct, elasticity-driven flow state in a yield-stress fluid in the absence of inertia. Numerical simulations show that this elasto-plastic turbulent state is characterized by a broad spectrum of fluctuations in velocity and stress. Results show a non-monotonic relationship between the volume fraction of the unyielded flow and plasticity. Surprisingly, we find that above a critical value of plasticity, the system can fluidize. Our results reveal the complex interplay between elasticity and plasticity in simple shear flows, indicating that plasticity can enhance rather than hinder momentum transport.

Elasticity theory rests on a constitutive relation between stress and strain relative to a reference state. Living matter, however, generates forces by motor molecule activity independent of strain, requiring a different approach to active tissue mechanics. We develop a theory of two-dimensional continuum mechanics in which the active force configuration, not a reference shape, is the fundamental input. Motivated by the cell-level Active Tension Network model for epithelia, we encode motor-driven intercellular forces in a Riemannian tension metric, whose mapping into physical space relates macroscopic stress to the microscopic tensions. Assuming force balance, we show that a stress-free reference state and an effective stress-strain relation emerge at the tissue scale, making the system an effectively elastic active solid. Extending from statics to dynamics, we show how such a solid can morph its shape through adiabatic evolution of active tensions. To capture plastic cell rearrangement, we introduce a second metric representing the cell adjacency graph in the continuum; topological rearrangement then appears as a continuous reparametrization of the tension manifold. The key fields characterizing the tissue's local mechanical state - tension anisotropy, macroscopic stress, and cell shape - arise from the discrepancies between the tension, adjacency, and physical metrics, represented mathematically by quasiconformal maps. Our theory explains how local contractility controls tissue shape and yields predictions distinct from existing models: tissues can remain rigid while "flowing", with a speed set by the rate of change of active forces rather than their magnitude, and shear flow can occur even under isotropic stress, since macroscopic stress is distinct from local tension anisotropy.

This study presents high-fidelity, two-way coupled fluid-structure interaction simulations to investigate the dynamic behavior of tandem perforated elastic vortex generators across a wide range of bending rigidity, mass ratio, and porosity, at a fixed Reynolds number and interspacing. Comparative simulations with non-perforated EVGs are also performed. Three response modes, lodging, vortex-induced vibration, and static reconfiguration, are observed in both configurations, while a distinct cavity oscillation mode emerges exclusively in non-perforated tandem EVGs. This mode is entirely suppressed with porosity due to disruption of the low-pressure cavity and increased flow transmission through pores. Frequency analyses reveal that vortex-induced vibration is consistently locked onto the second natural frequency, whereas the cavity oscillation mode is locked onto the first natural frequency and closely aligns with the first Rossiter mode, underscoring its distinct physical origin. Perforation modifies the natural frequency of the EVGs, shifting the lock-in and mode transitions toward lower bending rigidity and higher mass ratio values, and reducing oscillation amplitudes due to motion damping. Drag analysis shows consistently higher upstream drag due to wake shielding, while porosity reduces upstream drag and increases downstream drag by restoring streamwise momentum. Flow visualizations demonstrate that vortex shedding originates at the EVG tips, with perforated configurations producing smaller, more dissipative vortical structures. These results establish that porosity fundamentally alters dynamic regimes, suppresses cavity-driven instabilities, and enables passive modulation of wake dynamics in tandem EVG systems.

Rare-event searches including dark matter, coherent elastic neutrino–nucleus scattering (CE$\nu$NS), and neutrinoless double-beta decay (0$\nu\beta\beta$) require high-purity germanium (HPGe) detectors with ultralow noise, stable backgrounds, and electrode geometries that can scale to larger single-crystal masses. Ring-contact (ring-and-groove) designs address scalability by shaping the electric field to preserve low-capacitance readout, but their nonplanar topology motivates a lithium-contact process that is compatible with conformal deposition and robust high-voltage operation. As a process demonstration toward future ring-contact prototypes, we fabricate and characterize a hybrid-contact planar HPGe device, KL01. Here, “hybrid” denotes an $n^{+}$ contact formed by an in-house lithium-suspension paint followed by controlled thermal diffusion, combined with an AJA-developed a-Ge/Al $p^{+}$ contact and a-Ge sidewall passivation. At 77~K the device exhibits pA-scale leakage current under kV bias, a depletion plateau near $V_{\mathrm{dep}}\approx 1300$~V, and energy resolutions of 1.57~keV FWHM at 59.5~keV and 2.57~keV FWHM at 662~keV. These results validate the compatibility of the paint-and-diffuse lithium process with thin-film a-Ge/Al contacts and establish a practical fabrication workflow to be extended to ring-and-groove electrodes for next-generation rare-event HPGe modules.

Tweezer arrays of polar molecules present new opportunities for quantum science and quantum information. However, a major challenge, especially in bialkali molecule platforms, is the fact that current measurement schemes for the internal states are destructive. In this work, we present a method to use Rydberg atoms to nondestructively measure the internal state of a molecular qubit. We achieve this via microwave dressing of both molecules and Rydberg atoms, allowing us to tune the interactions so that there are minimal Rydberg-Rydberg interactions and many measurements can take place simultaneously. We consider two experimentally-motivated examples of detecting $^{23}$Na$^{133}$Cs and $^{87}$Rb$^{133}$Cs with $^{133}$Cs atoms. Finally, we discuss several strategies for mitigating various sources of crosstalk.

Time-periodic modulation of a static system is a powerful method for realizing robust unidirectional topological states. So far, all such realizations have been based on interactions among $s$ orbitals, without incorporating inter-orbital couplings. Here, we demonstrate higher-orbital Floquet topological insulators by introducing periodically modulated couplings between the optical $s$ and $p$ orbitals in a square lattice. The staggered phase of the $s$-$p$ couplings gives rise to a synthetic uniform $\pi$ magnetic flux per plaquette of the lattice, and periodic driving of the couplings opens a topological bandgap, characterized by the Floquet winding number. We image topological edge modes of $s$-$p$ orbitals traveling unidirectionally around a corner. Here, the topological phases are realized by a combined effect of the periodic driving and synthetic magnetic flux. Consequently, when the synthetic flux is turned off, the system becomes trivial over a range of driving parameters. Our results open a promising pathway for exploring topological phenomena by introducing the orbital degree of freedom.

Real-time data filtering and selection – or trigger – systems at high-throughput scientific facilities such as the experiments at the Large Hadron Collider (LHC) must process extremely high-rate data streams under stringent bandwidth, latency, and storage constraints. Yet these systems are typically designed as static, hand-tuned menus of selection criteria grounded in prior knowledge and simulation. In this work, we further explore the concept of a self-driving trigger, an autonomous data-filtering framework that reallocates resources and adjusts thresholds dynamically in real-time to optimize signal efficiency, rate stability, and computational cost as instrumentation and environmental conditions evolve. We introduce a benchmark ecosystem to emulate realistic collider scenarios and demonstrate real-time optimization of a menu including canonical energy sum triggers as well as modern anomaly-detection algorithms that target non-standard event topologies using machine learning. Using simulated data streams and publicly available collision data from the Compact Muon Solenoid (CMS) experiment, we demonstrate the capability to dynamically and automatically optimize trigger performance under specific cost objectives without manual retuning. Our adaptive strategy shifts trigger design from static menus with heuristic tuning to intelligent, automated, data-driven control, unlocking greater flexibility and discovery potential in future high-energy physics analyses.

Rapid and programmable shaping of light fields is central to modern microscopy, display technologies, optical communications and sensing, quantum engineering, and quantum information processing. Current wavefront shaping technologies face a fundamental dichotomy: liquid-crystal-on-silicon spatial light modulators (LCoS-SLMs) offer high pixel count but suffer from low refresh rates, while acousto-optic deflectors (AODs) provide moderate speed with restricted optical beam geometries. Though recent advances in photonic integrated circuits achieve fast switching, there is currently no tool that provides MHz-rate, continuous motion, and arbitrarily reconfigurable control over a set of diffraction-limited spots. Here we introduce a new class of spatial light modulator that provides both 2D pixel geometry and high speed. The device operates by encoding spatial information in frequency bins via a broadband optical phase modulator, and decoding them via a first-of-its-kind, high-resolution 2D spectrometer. The spectrometer, based on the architecture which we call the Re-Imaging Phased Array (RIPA), achieves its sensitivity through long path-lengths, enabled by intra-spectrometer re-imaging lens-guides. We demonstrate site-resolved optical pulsing with a 44(1)~ns rise time, corresponding to frame rates exceeding 10 million frames per second, as well as arbitrary, reconfigurable 2D addressing and multi-site operations, including asynchronous, independent beam motion, splitting, and recombination. Leveraging these tools opens new horizons in rapid optical manipulation of matter across science, from fast, scalable control that approaches the inertial and radiation limits of atoms in quantum processors, to dynamically programmable, microsecond-resolved illumination in microscopy and neuro-biological imaging.

Optical spectroscopy based on second-order nonlinearity is a critical technique for characterizing two-dimensional (2D) crystals as well as bioimaging and quantum optics. It is generally believed that second-harmonic generation (SHG) in centrosymmetric crystals, such as graphene and other bilayer 2D crystals, is negligible without externally breaking the inversion symmetry. Here, we show that with a new homodyne detection technique, we can apparently circumvent this symmetry-imposed constraint and observe robust SHG in pristine centrosymmetric crystals, without any symmetry-breaking field. With its exceptional sensitivity, we resolve polarization-resolved SHG in bilayer hexagonal boron nitride (h-BN), bilayer 2H-WSe$_2$, and remarkably, Bernal-stacked bilayer graphene, allowing us to unambiguously identify the crystallographic orientation in these crystals via SHG for the first time. We also demonstrate that the new technique can be used to non-invasively detect uniaxial strain and optical geometric phase in these crystals. The observed SHG in our experiments is attributed to second-order nonlinearity in the quadrupole channel, which is controlled by the presence of the $C_2$ symmetry instead of the inversion symmetry. Our new technique expands the capability of nonlinear optical spectroscopy to encompass a large class of centrosymmetric materials that could never be measured before, and can be used for quantum sensing of moiré materials and twisted epitaxial films.

This article presents an evaluation of off-the-shelf commercial accelerometers at the mixing chamber stage of a cryogen-free dilution refrigerator at temperatures down to 8 mK. In addition, we present results of radioassay of accelerometers using a high purity germanium detector counting setup. Cryogen-free dilution refrigerators using pulse-tube cryocoolers (PTs) – due to recent advances in their cooling capacity, long-term stability, and operational costs – have become ubiquitous tools in a wide range of fields ranging from experimental particle physics to quantum information sciences. However, vibrations induced by PTs can negatively impact the experimental payload in these applications. This work demonstrates that commercially available accelerometers can not only measure vibrations at millikelvin cryogenic temperatures but also pave the way for continuous, in situ, real-time vibration monitoring of dry dilution refrigerators. This monitoring capability facilitates applications such as real-time denoising for vibration-sensitive experiments, thereby enabling ongoing noise assessment and mitigation.

At scales larger than the forcing scale, some out-of-equilibrium turbulent systems (such as hydrodynamic turbulence, wave turbulence, and nonlinear optics) exhibit a state of statistical equilibrium where energy is equipartitioned among large-scale modes, in line with the Rayleigh-Jeans spectrum. Key open questions now pertain to either the emergence, decay, collapse, or other nonstationary evolutions from this state. Here, we experimentally investigate the free decay of large-scale hydroelastic turbulent waves, initially in a regime of statistical equilibrium. Using space- and time-resolved measurements, we show that the total energy of these large-scale tensional waves decays as a power law in time. We derive an energy decay law from the theoretical initial equilibrium spectrum and the linear viscous damping, as no net energy flux is carried. Our prediction then shows a good agreement with experimental data over nearly two decades in time, for various initial effective temperatures of the statistical equilibrium state. We further identify the dissipation mechanism and confirm it experimentally. Our approach could be applied to other decaying turbulence systems, with the large scales initially in statistical equilibrium.

Experiments were conducted to investigate characteristics of turbulent spots formed in transitional boundary layers developed over a flat plate and an axisymmetric cone placed in similar hypersonic freestream environment of Mach number 5.85. The freestream Reynolds number in the present work varied between $3.0-6.0\times10^6$/m. Heat transfer measurement along the surface of both the test models was used to ascertain the state of boundary layer and to calculate the intermittency associated with transitional boundary layer. Turbulent spots generated in the transitional boundary layer were characterized in terms of their leading-trailing edge velocities, their streamwise length scales and their generation rates on both the test models. Leading edge of the turbulent spots developed over both the test models were found to be convecting at a speed equivalent to 90% of the boundary layer edge speed. The trailing edge of the spots developed on a planar boundary layer traversed at a lower speed than its axisymmetric counterpart. Streamwise length scales of a turbulent spot developed in a planar boundary layer grew at a higher rate when compared with axisymmetric boundary layer. Turbulent spot generation rates for both planar and axisymmetric boundary layers was found to be in the range of $1000000-3000000$ spots/m/s.

This perspective introduces attosecond path qubits: measurement-defined two-level subsystems that arise naturally in strong-field physics from the coherent interference of distinguishable quantum pathways. These effective qubits are dynamical superposition states formed during laser-driven sub-cycle electron motion and appear in diverse settings, including short-long trajectories in high-harmonic generation (HHG), early-late ionization bursts in multicolor fields, polarization-selective recombination channels, and momentum or energy-bin interference in above-threshold ionization (ATI). Attosecond qubits can be prepared, coherently manipulated, and read out using existing attosecond techniques, providing a compact Hilbert-space description of strong-field dynamics beyond semiclassical trajectory pictures. A density-matrix formulation makes explicit the roles of coherence, dephasing, and decoherence, arising from continuum propagation, Coulomb interaction, infrared dressing, and macroscopic averaging, within a reduced description that remains far from thermalization. The attosecond qubits framework identifies new opportunities for ultrafast coherence metrology and for probing open quantum dynamics in strongly driven, time-dependent Hamiltonians.

Biased sampling in molecular dynamics simulations overcomes timescale limitations and delivers free-energy landscapes, essential to understand complex atomistic phenomena. However, when applied across diverse systems and processes, biasing protocols often require time- and resource-consuming fine-tuning. In search for robustness, we boost a prominent biasing method, Umbrella Sampling. To estimate the value of an integral, i.e., the free energy, our Bayesian Umbrella Quadrature (BUQ) method iteratively selects gradient samples, i.e., bias locations, that most reduce the posterior integral variance based on a noise-tolerant Gaussian process model, which also effectively interpolates between samples. We validate the method for a conformational change in a small peptide, a water-to-ice phase transition, and a substitution chemical reaction; obtaining excellent accuracies and speedups. To ease adoption of this more automated and universal free-energy method, we interface BUQ with wide-spread simulation packages and share hyperparametrization guidelines.

Urban scaling theory posits that urban indicators follow power-law relations with population, yet the evolution of these patterns - and the role of regional differences in settings marked by social inequalities and unplanned urbanization - remains poorly understood. Here, we analyze nearly three decades of mortality data from Brazilian cities to investigate the scaling of external causes of death: homicides, suicides, and accidents. Using a hierarchical Bayesian framework and spatial correlation analysis, we find that these mortality indicators exhibit distinct, regionally heterogeneous scaling trajectories. Homicide mortality has significantly attenuated its typical superlinear scaling with increased spatial clustering, suggesting a redistribution of violence to smaller cities and intensified intercity interactions, possibly linked to the consolidation of organized crime. Suicide mortality, usually sublinear, has trended upward, implying a weakening of urban agglomerations' protective effect. Accident mortality remains superlinear, with transport fatalities scaling nearly proportionally, and non-transport accidents becoming superlinear. The scaling changes for suicides and accidents coincide with less correlated and stable spatial patterns, suggesting that the underlying processes predominantly operate within city boundaries. Finally, while scaling exponents have evolved more homogeneously across Brazilian states, scale-adjusted mortality remains highly heterogeneous, indicating that fundamental processes govern scaling laws, whereas state-specific factors drive scale-adjusted metrics.