Ideally, the characterization of non-classical states requires measurements on timescales much shorter than the system’s decoherence time. However, in quantum cavity electrodynamics, photon loss rates are often comparable to measurement rates, which degrades the fidelity of the readout. In this work, we propose an active protocol to accelerate the phase estimation of squeezed vacuum states trapped in a lossy cavity. Instead of relying on passive leakage or linear coherent driving, we excite the system with a time-optimized degenerate parametric drive. This adapted two-photon pump actively amplifies the relevant quantum fluctuations, rapidly projecting the phase information of the squeezed state onto the integrated homodyne photocurrent of the output field before significant decoherence occurs. Because a squeezed vacuum carries no phase information in its first moments, this quadratic control is the minimal resource able to imprint the squeezing angle onto the detected signal. Using a numerical optimal control approach, we derive pumping envelopes that maximize the ability to distinguish between orthogonal squeezed states, achieving approximately a 6.02-fold increase in signal contrast compared to constant excitation schemes. We demonstrate that this active extraction protocol produces a strictly monotonic calibration curve, enabling rapid and unambiguous identification of the squeezed phase angle. Furthermore, robustness analysis confirms that the phase estimate remains reliable even in the presence of intense Gaussian detection noise, providing a practical framework for rapid state verification in open-system quantum technologies.
Phase transitions play a central role in statistical physics and are well understood in systems at thermal equilibrium. However, their nonequilibrium counterparts remain less explored because of the lack of a unified theoretical framework. In this study, we examine the potential of deep learning, specially convolutional neural networks (CNN), to detect nonequilibrium phase transitions (NEPT) in a 2D Ising model-like square lattice ferromagnetic system under effective parameter $h$ . Without this parameter ( $h = 0$ ), we generate equilibrium spin configurations using the standard Metropolis algorithm as usual. With $h\ne 0$ , we generate nonequilibrium spin configurations using an effective Glauber update rule which breaks detailed balance. While the former is used to train CNN, the later is not subsequently described by the usual Boltzmann-Gibbs distribution rather used to test the model. The study shows that the trained CNN can distinguish between ordered and disordered nonequilibrium steady states and accurately predict the critical temperature of the system undergoing NEPT. Finite size scaling analysis of the model’s output (perdition) reproduces critical exponents that agree with theoretical expectations, indicating that this method provides a strong, data driven approach for examining nonequilibrium critical phenomena.
We formulate matter scale field as a relativistic framework in which a homogeneous scalar field controls the evolution of the physical metric and material standards through one common scale. Cosmological redshift is interpreted as a comparison between propagated light and material standards whose scale has evolved between emission and detection. The action is written on a single physical metric $g_{\mu\nu}$ : gravity, electromagnetism, the Standard Model, clocks and rulers, emission and detection are all defined on this metric. Consequently, the local Standard-Model description, local Lorentz invariance, universal matter coupling and the operational meaning of dimensionless constants are preserved. For a homogeneous solution, we write $g_{\mu\nu}(t) = b(\phi(t))^2g^0_{\mu\nu}$ , where $b(\phi) \gt 0$ is the scalar-controlled metric scale and $g^0_{\mu\nu}\equiv g_{\mu\nu}(t_0)$ is the physical metric at the present epoch, with $b(\phi(t_0)) = 1$ . When the same action is expressed relative to the present value, source-free Maxwell propagation contains no explicit factor $b(\phi)$ , whereas the coefficients setting the Higgs vacuum scale, generated particle masses and atomic transition frequencies acquire the corresponding powers of $b(\phi)$ . Particle masses and atomic frequencies therefore scale with $b(\phi)$ , while material lengths scale as $b(\phi)^{-1}$ . A photon emitted at $t_\textrm{em}$ has a present-calibrated frequency proportional to $b_\textrm{em}$ , which is conserved during source-free propagation. At observation, it is compared with the present material standard proportional to $b_0$ , giving $1+z = b_0/b_\textrm{em}$ . Light-curve time dilation and the Friedmann–Lemaitre–Robertson–Walker distance relations follow from the physical metric. We derive the homogeneous kinematics, physical-metric action and Standard-Model scale organization behind this mechanism. For a canonical scalar, a log-linear field-to-scale map yields a model-specific expansion and distance–redshift relation directly testable against $\Lambda$ CDM and other background cosmologies. Cosmological perturbations, structure growth, gravitational lensing and CMB anisotropies are decisive tests of the framework.
We investigate the propagation of structured scalar optical beams in an effective anisotropic background inspired by the scalar sector of the Standard-Model Extension and controlled by a single dimensionless parameter λ. The physically relevant configuration is a transverse radial director field that modifies the radial part of the Helmholtz operator while preserving axial symmetry. Starting from the Green-function representation, we cast the propagation problem as an initial-value spectral reconstruction of a prescribed finite-aperture entrance profile at z=0 and verify that this profile is recovered at the launch plane across the values of λ used in the analysis, within small numerical error. We use the Laguerre–Gaussian mode L_3 as the representative vortex-free Laguerre case, retain L_4 only as a quantitative benchmark for radial-order dependence, and compare both with a Bessel–Gaussian beam of input order m=0. The effective anisotropy produces a systematic redistribution of radial intensity, determines whether the central peak remains dominant or is overtaken by off-axis maxima as propagation advances, and controls the radial displacement of the dominant side lobes. For the finite-aperture Bessel–Gaussian beam, the same parameter quantifies how the approximately diffraction-resistant ring structure broadens for negative λ and compresses for positive λ during propagation.
Local arguments based on the equivalence principle are often used to motivate gravitational redshift, light bending, and other weak-field effects without invoking the full Einstein field equations. Such arguments are physically suggestive, but they do not, by themselves, determine the exterior metric of a gravitating body. This technical note provides a diagnostic of a local-equivalence ansatz closely related to the Mociuţchi metric. Starting from a local special-relativistic interpretation and the energy ansatz $E(1+\Phi/c^2) = E_\infty$ , with the ‘Newtonian potential’ proxy $\Phi = -GM/R$ , one obtains the clock and radial ruler factors $1-GM/(c^2R)$ . If these factors are promoted to a static, spherically symmetric line element, the result is \begin{align*} \mathrm{d} s^2 = {}\left(1-\frac{GM}{c^2R}\right)^2c^2\mathrm{d} T^2 -\frac{\mathrm{d} R^2}{\left(1-\frac{GM}{c^2R}\right)^2} {}-R^2\mathrm{d}\Omega^2 .\end{align*} The ansatz agrees with the Schwarzschild metric at leading weak-field order and reproduces some familiar first-order intuition. Its post-Newtonian expansion gives $\gamma = 1$ and $\beta = 3/2$ , in contrast with the general-relativistic values $\gamma = \beta = 1$ for an uncharged vacuum exterior. It follows that the perihelion correction is $5/6$ of the Schwarzschild prediction; for Mercury this gives $35.82$ arcsec per century instead of $42.98$ . The same ansatz shifts the horizon, photon sphere, and innermost stable circular orbit to smaller areal radii than in Schwarzschild, and gives a smaller critical impact parameter. These diagnostics suggest that local-equivalence heuristics can reconstruct first-order behavior, although they do not by themselves provide the Schwarzschild exterior metric unless further conditions recover the observed post-Newtonian structure.
The BARC-TIFR Pelletron Linac Facility, a key centre for heavy ion research in India, routinely delivers a variety of ion beams from Li to Cl with $E\sim5-8$ MeV A $ ^{-1}$ for experiments. The energy of ion beams from 14UD Pelletron is boosted with a superconducting linac ( $\beta_\mathrm{opt}$ = 0.1, lead-plated copper cavities operating at $\sim$ 150 MHz). A program to incorporate niobium low-beta ( $\beta_\mathrm{opt}\,\sim$ 0.07) quarter wave resonators (QWRs) at the entrance linac module to broaden the mass acceptance of the linac has been initiated. This program is an important step forward towards advancing the heavy ion research in India. The design study of the low beta QWR is presented in this article along with RF measurements on the prototype QWR to qualify the design parameters.
This article gives a self-contained geometric formulation of electrostatics on closed Riemannian surfaces. On a compact surface without boundary, Gauss’s law imposes a global compatibility condition: the total charge must vanish. Hence an isolated nonzero point charge is incompatible with the closed geometry unless it is neutralized by a compensating background. The appropriate replacement for the Euclidean Coulomb kernel is the normalized Green function of the Laplace–Beltrami operator, obtained by removing the constant zero mode. Within this framework, we organize the analytic structures needed for closed-surface electrostatics. These include solvability of the Poisson equation for mean-zero sources, the Hodge decomposition of smooth $1$ -forms, the resulting classification of smooth electrostatic fields, spectral and heat-kernel representations of normalized Green functions, and the Robin function as the diagonal regular part of the Green kernel. In two dimensions, the Robin function gives the renormalized self-energy of a neutralized point charge. We also derive the conformal transformation laws for the normalized Green function and the Robin function, together with the corresponding conformal-response formula for compact-surface Coulomb Hamiltonians. The general framework is illustrated on several representative closed surfaces. For the round sphere and for flat tori, we give explicit formulas for the normalized Green kernel; on flat tori, the area-normalized Fourier representation is compared with the Jacobi theta-function representation. For compact Riemann surfaces of higher genus, we recall the construction of the canonical Arakelov Green function from the prime form, including the Abel–Jacobi quadratic correction. As an application, we formulate the two-dimensional one-component plasma on a compact surface in terms of the normalized Green kernel and the Robin self-energy. We prove a leading $N^2$ -scale mean-field equilibrium theorem for this model: the normalized Riemannian area measure is the unique leading-order equilibrium measure, and asymptotically minimizing configurations equidistribute with respect to it. The paper thus provides a unified and explicit reference framework for Coulomb-type interactions on closed curved surfaces.
Measuring the difference between integrable functions or probability distributions is central to analysis, information theory, and physics. Classical distances and divergences provide global measures of discrepancy, but do not indicate how differences are distributed across intrinsic structural or informational resolutions. As a result, distributions that differ substantially in their internal organization may appear indistinguishable under standard metrics. This paper develops an entropy-visible multiscale representation for comparing nonnegative $L^1$ functions. Building on an entropy-driven hierarchical decomposition, each function is represented by a canonical sequence of step-function approximations in which refinement occurs only when genuine entropy-visible nonuniformity is present. Using these representations, we define finite-depth and infinite-depth pseudo-metrics that compare functions by resolving and accumulating discrepancies as entropy-defined distinctions become visible. Unlike single-scale distances, the proposed metric distinguishes purely coarse differences from structural disagreements that persist across resolutions. The representation further admits a canonical localization by scale and region, yielding an explicit description of where and by how much two functions differ in an information-theoretic sense. This provides a principled, entropy-aware notion of distance suited to coarse-graining and multiscale analysis in physical systems.
We study a thermally driven nematohydrodynamic model obtained by coupling Boussinesq convection to a Ginzburg–Landau relaxation of the director field. We prove the fundamental energy–dissipation identity, construct global weak solutions in three spatial dimensions, and establish uniqueness in two dimensions. A Serrin-type criterion is stated that upgrades weak solutions to strong solutions under a Prodi–Serrin integrability condition on the velocity. For Rayleigh–Bénard geometry with stress-free isothermal boundaries, we show that a uniformly aligned conduction state has the same linear onset threshold as the classical Boussinesq problem and that the nonlinear energy stability threshold coincides with the linear one, hence excluding subcritical instabilities for this model.
To investigate the potential for stable negative capacitance (NC) and better electrostatic control, a systematic study of cylindrical ferroelectric-dielectric heterostructures with diverse ferroelectric stacking configurations is presented. The cylindrical geometry is chosen because it provides better gate-to-channel control than traditional planar structures. By evaluating both FE-DE and FE-FE-DE configurations, our analysis clarifies how ferroelectric stack engineering impacts capacitance enhancement, voltage amplification, and the overall stability of the NC state. First an isolated cylindrical ferroelectric capacitor is studied to test the NC behavior, followed by the introduction of a dielectric layer in series to ensure stable operation. Of the materials investigated, Zr doped HfO2 demonstrates the best performance, exhibiting superior internal voltage amplification, strong NC stabilization and enhanced capacitance. Furthermore, our results indicate that the FE-FE-DE heterostructures consistently outperforms simpler FE-DE structures. To validate these findings at the circuit level, we integrated these optimized heterostructures into a baseline MOSFET framework and tested them using a resistive load inverter, confirming that Zr doped HfO2 based systems deliver the most effective performance for MOSFET applications.
Weak values characterize quantum systems that are both pre- and post-selected. Such systems are described by two wavefunctions, the overlap of which defines the success probability of the experiment. In weak value theory, it is usually assumed that the weak value does not exist for zero-overlapping pre- and post-selected wavefunctions. In this paper, we show that weak values can be defined even when the success probability of the experiment tends to zero. We call such weak values impossible. Standard quantum expectation values can be constructed from weak values. Remarkably, impossible weak values vanish in the expectation value, but may appear in its dynamics. We show that impossible weak values are not unique for a given pre- and post-selected state pair. They depend on the path in state space along which the pair is approached.
The effect of biaxial strain on the quantum capacitance of two-dimensional NbSe2 was investigated via density functional theory calculations. Its two known polytypes, 1H and 1T, were found to have metallic electronic band structure under the Perdew-Burke-Ernzerhof exchange-correlation functional, consistent with previous results, implying that these two-dimensional materials are feasible supercapacitor electrodes. The quantum capacitance for both the 1H and 1T structural phases of NbSe (2) is found to improve as they are subjected to increasing biaxial tensile strain. On the contrary, increasing the biaxial compressive strain tends to decrease the quantum capacitance. Analysis of their density of states profile revealed that biaxial tensile strain induced the formation of localized states especially near the Fermi level, and the shifting of DOS peaks toward the Fermi level. These were proposed to explain the enhancement of quantum capacitance for both the 1T and 1H structural phases of NbSe (2). These results highlight the utility of biaxial strain in fine tuning and controlling quantum capacitance, and could potentially be of importance in the design and engineering of low-dimensional supercapacitors for nanoelectronics applications.
The current paper describes new transformations that determines all possible ways that the partial differential equation, ut=sigma 2xjuxx+g(x,t)u, becomes the heat transfer equation. Typically, the approach contains unknown functions of integration, which can be obtained by specific auxiliary equations. As an important result, fundamental solutions can be found analytically. The technique is systematic and avoids the need for computer algebra-demonstrating a potent relationship between theory and practice. This study contributes to analytical techniques by offering new pathways to overcome problem solving.
This work presents the results of a study on the electronic energy structure of La-doped gallium arsenide (GaAs). The electronic energy spectrum was calculated within the framework of density functional theory. Furthermore, the concentration dependence of the main energy and optical properties of Ga1-xLaxAs was established for La concentrations ranging from x = 0 to 0.25. An analysis of the energy band dispersion and density of states was performed. Based on the electronic energy spectrum, the real and imaginary components of the dielectric function were calculated for the studied samples. Using the Kramers-Kronig relations, fundamental optical functions, such as the refractive index (n), extinction coefficient (k), and absorption coefficient (alpha) were derived. The concentration dependence of these optical functions was established, followed by a comparative analysis with existing literature data.
We examine a coupled Allen-Cahn system that generalizes the classical Allen-Cahn equation, consisting of two interacting components with coupling parameters lambda,gamma>0. We provide a complete classification of critical points, identifying nontrivial equilibria for lambda gamma not equal 1 and a continuum of equilibria when lambda=gamma=1. Stability is analyzed from temporal, spectral, and spatial steady-state perspectives, demonstrating asymptotic stability for lambda gamma<1 and instability for lambda gamma>1. The steady states exhibit center or saddle behavior depending on the coupling regime. Numerical visualizations of equilibrium maps and phase-plane vector fields illustrate how stability and bifurcation patterns vary across the (lambda,gamma)-plane.
Accurate and efficient determination of beam phase space is essential for the operation of high-intensity proton accelerators such as the 20 MeV low energy high intensity proton accelerator (LEHIPA) at Bhabha Atomic Research Centre. Conventional solenoid scan techniques, though widely adopted, are limited by their sensitivity to noise, computational overhead, and difficulties in handling nonlinear beam dynamics. In this work, we present a dual-network machine learning (ML) framework. This framework consists of two cascaded neural networks (NNs): Model 1, an emittance prediction model that uses root-mean-square (RMS) beam size data and current to predict beam emittance, and Model 2, a Twiss parameter prediction model that incorporates the predicted emittance, beam current, and multiple RMS beam size measurements to predict the beam's Twiss parameters (alpha, beta). The emittance model is pre-trained using a physics-informed approach that leverages an analytical envelope equation model. This pre-training embeds beam physics into the NN, reducing the need for large volumes of expensive simulation data and ensuring physically consistent predictions. The model is then fine-tuned using high-fidelity data from TraceWin beam dynamics simulations. The framework is subsequently validated against experimental data from the LEHIPA facility. Our results confirm that this ML approach provides reliable and accurate beam parameter predictions. This methodology offers significant advantages in prediction speed, computational efficiency, and operational flexibility compared to traditional methods. The successful implementation of this ML framework demonstrates its high potential for real-time beam diagnostics and automated accelerator tuning in future high-current accelerator facilities.
The advent of quantum computing necessitates the transition from conventional encryption systems to quantum-resistant alternatives. Quantum key distribution (QKD) represents one such approach. Nevertheless, fibre-based QKD is constrained by severe limitations in transmission distance. A promising solution is satellite-based QKD, wherein a satellite establishes secure communication with a ground station. However, daylight presents a considerable challenge for QKD devices, which are highly sensitive to ambient light. Implementing satellite-based QKD in Arctic regions is particularly compelling due to their distinctive annual cycle and prolonged periods of darkness; yet, this possibility has received limited attention in the existing literature. This study assessed the feasibility of satellite-based QKD in regions above the Arctic Circle by simulating a satellite QKD link to three ground stations located in Finnish Lapland: Rovaniemi, Sodankyl & auml;, and Utsjoki. The simulation tool comprised MATLAB code for modelling the quantum link, satellite orbital data generated using the Python Skyfield library, and local weather data collected for the year 2024, including cloud cover, rain, snow, ice crystals, and fog. Our findings suggest that while the polar night provides favourable conditions for wintertime quantum communication, continuous daylight during summer and high cloud-cover probabilities may lead to extended service interruptions, severely limiting the achievable secret key material. Optimizing satellite overpass timing substantially reduces outage periods caused by background light; however, this optimization becomes ineffective during summer months due to the persistently high ambient light levels. These constraints underscore the need for robust key-storage mechanisms and careful evaluation of potential use cases. It is recommended that advanced filtering techniques be investigated as a potential means to mitigate summer outage periods caused by excessive ambient light.
Two criteria for the spectra of relativistic waves are proposed. Zero-point radiation provides the identity representation of the conformal group in Minkowski spacetime. Thermal radiation provides the irreducible representation of the conformal group in Minkowski spacetime which involves exactly one scaling parameter (the temperature) which is also time-stationary in a Rindler frame. Zero-point radiation is the limit of thermal radiation as the temperature goes to zero. Crucially, both zero-point radiation and thermal radiation take basically the same functional form in a Rindler frame. For relativistic scalar waves, a full derivation of the Planck spectrum including zero-point radiation is obtained within the classical theory.
Achieving low-emittance, high-intensity beams remains a critical challenge for next-generation high intensity proton accelerators. This paper presents a comprehensive design and advanced simulation analysis of a compact tetrode extraction system for a novel 2.45 GHz multi-cusp Electron Cyclotron Resonance (ECR) proton source developed as a parallel injector for Medium Energy High Intensity Proton Accelerator (MEHIPA). The system utilizes a zero-axial-field configuration to minimize magnetic contributions to the beam emittance. A dual-simulation methodology is implemented: IBsimu is used for initial geometric optimization and parametric analysis, followed by detailed studies of multi-species extracted beam in CST Microwave Studio (MWS) and the integration of Monte Carlo Collision (MCC) modelling in its Particle Tracking Solver (PTS). This combined approach allows accurate modelling and provides a better visualisation of complex phenomena, including multi-species co-extraction and the crucial effects of space-charge compensation (SCC) on the extracted beam. The optimized compact tetrode geometry (total length similar to 45 mm) is capable of delivering 12-15 mA of H+ current at 30 keV with a normalised emittance of 0.1 pi-mm-mrad. These results provide detailed design insights and optimization strategies that can guide the development of high brightness ion sources with optimized beam quality.
