Computational Physics · Cross-listed from quant-ph
Open quantum systems beyond equilibrium: Lindblad equation and path integral molecular dynamics
Benedikt M. Reible, Somayeh Ahmadkhani and Luigi Delle Site
The Lindblad equation determines the time
evolution of the density operator of open
quantum systems. While valid for any system size, its use is, in practice, restricted to prototype/surrogate models with the aim of tackling specific aspects of the overall
quantum complexity of a multi-atomic system. Path integral molecular dynamics (PIMD) instead provides static and dynamical
quantum statistical averages of physical observables for systems in
equilibrium composed of up to thousands of atoms over timescales up to nanoseconds, under the condition that short-time
quantum coherence is not relevant for the properties of interest. PIMD relies on the well-established technique of molecular dynamics (MD) with its associated classical trajectories. However, it cannot describe a direct time
evolution of a system and its convergence to a stationary state in situations out of
equilibrium. In this work, we analyze the link between the Lindblad equation and PIMD; specifically, we will discuss how PIMD can actually be used to calculate the time
evolution of ensemble-averaged physical observables and their convergence to a stationary state for situations out of
equilibrium, bypassing the need of explicitly solving the Lindblad equation. Yet, at the same time, the Lindblad equation and PIMD are linked to one another through a formal relation of equivalence, which provides an argument for the consistency of PIMD results, namely the positivity of the density operator at any time. A numerical study of a prototype system, which is of interest in chemical physics, will be used to showcase the method.
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Computational Physics · Cross-listed from cond-mat.mtrl-sci
Ab initio informed electronic stopping models for light ion propagation in metals
Evgeniia Ponomareva, Artur Tamm and Andrea E. Sand
Understanding ion-matter interactions at the atomistic level is key to advancing materials for the
semiconductor industry, space systems, and
nuclear fusion technologies. However, most atomistic frameworks still rely on simplified descriptions of how ions transfer energy to the electronic subsystem, overlooking the sensitivity of this process to the actual ion path. Existing electron-ion interaction models, such as the tensorial unified two-temperature model, were developed to study self-irradiation scenarios, but their suitability for light-ion irradiation remains unexplored. Here, we propose that for light projectiles, stepping back from the tensorial formulation toward a simpler, local model of electronic stopping provides a more efficient and physically transparent trajectory-dependent description. We parameterize and validate both models for hydrogen and helium in tungsten using ab initio electronic stopping data and large-scale ion range simulations, benchmarked against existing experimental data. This provides a consistent framework for including nonadiabatic electronic stopping in atomistic simulations of light-ion energy dissipation.
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Optics
Photonic nanojets as emergent free-space power flux funnels
Mirza Karamehmedović, Cristian Placinta, Tobias Abilock Mikkelsen et al. (+1 more)
A reduced local field model derived from full-wave electromagnetic simulations shows that photonic nanojet formation corresponds to an emergent mesoscopic funnel of propagating power flux sustained by an effective free-space transverse mode structure. This interpretation moves beyond purely
geometric-optics or interference-based explanations by identifying a self-consistent redistribution of phase gradients and effective longitudinal wavenumber near the nanojet waist. The model quantitatively captures characteristic nanojet morphology, including the formation and local structure of the jet waist. It also yields a geometry-independent lower bound on the nanojet waist, linking transverse confinement to the effective axial wavenumber through an explicit trade-off. The model establishes a direct connection between full-wave Maxwell fields and a reduced free-space oscillator description, yielding new physical insight into nanojet confinement and suggesting design principles for nanojet-assisted imaging, lithography, and subwavelength field localization.
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All authors Mirza Karamehmedović, Cristian Placinta, Tobias Abilock Mikkelsen, Jesper Glückstad
Atomic Physics
Partial ionisation cross sections for the binary-encounter Bethe model
Anthony Jeseněk, Alejandro Luque and Nikolai Lehtinen
The original binary-encounter Bethe model of Kim and Eugene Rudd (1994 Phys. Rev. A 50 3954-67) has proven to be an accurate analytical representation of total impact ionisation cross sections of electrons colliding with atoms and molecules. It is based on a decomposition into partial ionisation cross sections from electrons in bound orbitals. Despite the model's accuracy for total ionisation, its individual partial cross sections for ionisation rely on thresholds calculated theoretically which systematically overestimate the experimental orbital binding energies. Here, we examine the BEB model's performance when based on experimental ionisation thresholds. The resulting partial cross sections of the various final (excited) ionic states produced could help to prefigure subsequent optical radiations and non-radiative transitions in models of
plasma physics.
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Fluid Dynamics
Denoising diffusion and latent diffusion models for physics field simulations
Yuan Jia, Chi Zhang, Hao Ma et al. (+3 more)
Accurate prediction of physical fields is critical in various engineering applications, including thermal management in electronic systems, airfoil shape optimization in aerospace, and flow field control in hypersonic vehicles. This study employs the Denoising
Diffusion Probabilistic Models (DDPMs) for predicting the temperature field caused by the thermal
diffusion, and the flow fields spanning from incompressible to hypersonic regimes. A conditional DDPM framework is first validated with a steady-state thermal
diffusion problem by predicting the temperature distribution around a plate with holes. Strong agreement with ground truth data is shown with an average error of approximately 0.013 for plates with a central circular hole. The model also delivers high accuracy in critical regions, such as near the inner circular or square holes. Its performance is further evaluated on incompressible flow around an airfoil and hypersonic flow over a compression ramp, confirming robust predictive capability across diverse flow conditions. Additionally, a latent-space implementation of DDPM is introduced, which employs an Autoencoder (AE) for dimensionality reduction and reconstruction of the physical data. The resulting Latent
Diffusion Model (LDM) maintains reconstruction quality comparable to the standard DDPM while substantially reducing the computational cost of the
diffusion training process. When applied to hypersonic flow over a compression ramp in the original parameter space, LDM predictions align well with ground truth, achieving a deviation of only 4.28% in separation length estimation. This work confirms the high predictive accuracy of the DDPM framework and highlights the efficiency gains from performing
diffusion in a learned latent space. The findings establish an efficient framework for high fidelity generative modeling of complex thermal/flow fields.
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All authors Yuan Jia, Chi Zhang, Hao Ma, Qiao Zhang, Kai Liu, Chih-Yung Wen
Optics · Cross-listed from quant-ph
Quantum Limits of Passive Optical Surface Metrology and Defect Detection
Jernej Frank, George Brumpton, Tommaso Tufarelli et al. (+2 more)
We develop a
quantum statistical framework for passive optical surface metrology. Modelling a surface as an incoherent ensemble of point emitters imaged through a diffraction-limited system, we employ techniques from
quantum parameter estimation and hypothesis testing to derive ultimate bounds for jointly estimating geometrical features and for deciding the presence or absence of surface defects, and we identify optimal measurements from the geometry of the point-spread-function
manifold. As a representative application, we analyse a minimal surface crack model based on three point sources and show that spatial mode sorting can simultaneously enable near-
quantum-limited estimation of crack width and depth and markedly enhanced detectability of the crack, compared with direct imaging. Our results pave the way towards enhanced optical inspection and characterisation of sub-diffraction surface features by probing a limited number of spatial modes without any illumination control.
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All authors Jernej Frank, George Brumpton, Tommaso Tufarelli, Gerardo Adesso, Samanta Piano
Applied Physics
Revealing Magnon-Photon Coupling in Ultrathin Magnetic Films Using the Derivative-Divide Method
Kang An, Zhenhui Hao, Yongzhang Shi et al. (+4 more)
Magnon-
photon coupling in planar cavities provides a promising platform for integrated cavity magnonics devices. However, its characterization becomes challenging in ultrathin
magnetic films because their weak
magnetic response can be obscured by the much stronger microwave background. Here, we employ the derivative-divide method to extract the field-dependent
magnetic response from transmission measurements of split-ring resonators. The method reveals clear magn-
photon anticrossings that are hardly discernible in conventional transmission spectra and enables quantitative extraction of the coupling strength. We resolve coupling in yttrium iron garnet films down to 60 nm and extend the approach to conductive CoFeB films down to 5 nm. Our results demonstrate a practical method for characterizing magno-
photon coupling in ultrathin
magnetic films, providing an experimental route toward cavity magnonics systems based on ultrathin
magnetic films.
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All authors Kang An, Zhenhui Hao, Yongzhang Shi, Yingjie Zhu, Xiling Li, Chi Zhang, Guozhi Chai
Space Physics
Auroral Acceleration Generates Electron Beams in Jupiter's Middle Magnetosphere
June Piasecki, Joachim Saur, George Clark et al. (+3 more)
Observations made by the Juno spacecraft above Jupiter's polar regions have revealed that electrons accelerated toward Jupiter, which contribute to auroral emissions, are frequently accompanied by electrons accelerated away from Jupiter. These electrons should be observable as narrow electron beams in the middle magnetosphere, in accordance with the principles of adiabatic particle motion. The existence of such beams has been previously reported using data from the Galileo mission, and their relation to auroral processes has been hypothesized. In the present study, we analyze electrons measured by Juno's JEDI instrument in the middle magnetosphere between 13 RJ and 50.5 RJ radial distance and within energies of 30-1,200 keV. The pitch angle distributions of potential electron beams are fitted with an intensity 'beamness' function. The presence of narrow beams is demonstrated throughout the observation range. The energy fluxes of auroral and equatorial electron beams are compared by including pitch angle scattering processes along the magnetospheric field lines. This is achieved by solving the pitch angle
diffusion equation for different sets of
diffusion coefficients. The statistical occurrence distribution and the energy fluxes of the beams are consistent with auroral upward accelerated electrons observed in studies of the polar space environment. This finding provides further support for the hypothesis that the electron beams observed in the middle magnetosphere originate from the auroral acceleration region.
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All authors June Piasecki, Joachim Saur, George Clark, Barry H. Mauk, Annika Salveter, Jamey Szalay
Physics and Society
A Survey on Algorithmic Interventions in Opinion Dynamics
Atsushi Miyauchi, Yuko Kuroki, Federico Cinus et al. (+2 more)
Social media platforms have become critical infrastructures for public communication, where large-scale interaction can both support socially beneficial collective pressure and amplify polarization and conflict. While opinion-dynamics research has long modeled how beliefs evolve through interpersonal influence, the central challenge for healthier online environments increasingly lies in algorithmic interventions: mechanisms that steer collective opinion toward desirable outcomes or dampen harmful dynamics. This survey offers a structured synthesis of this fast-growing, interdisciplinary literature. We organize prior work by the objective optimized – overall opinion (e.g., consensus or mean opinion), polarization and disagreement, and other quantities – and review the associated optimization formulations and representative
algorithms with mathematical rigor. We also compile intervention-relevant theoretical and empirical findings. Finally, we outline concrete future directions that emerge from this survey.
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All authors Atsushi Miyauchi, Yuko Kuroki, Federico Cinus, Stefan Neumann, Francesco Bonchi
Atomic Physics
Zero crossings of the differential scalar polarizability of Ba$^+$ clock transition
N Jayjong, M D K Lee, K J Arnold et al. (+1 more)
The differential scalar polarizability $\Delta\alpha_0(\omega)$ of the Ba$^+$ S$_{1/2}$-to-D$_{5/2}$ clock transition has a zero crossing near 481nm, which is measured to be 623.603\,13(17)\,THz. From this measurement, we infer a ratio of reduced
matrix elements $\langle P_{3/2}\|r\|S_{1/2}\rangle/\langle P_{1/2}\|r\|S_{1/2}\rangle=1.411\,81(13)$, which provides a stringent test of atomic structure calculations and experimental determination of
matrix elements. Additionally, it enables the construction of an accurate approximation to $\Delta\alpha_0(\omega)$, valid for frequencies up to 450\,THz, with only one reduced
matrix element, $\langle P_{1/2}\|r\|S_{1/2}\rangle$, appearing in the model's parameterization. We discuss the achievable accuracy of the model, the application to the assessment of blackbody radiation (BBR) shifts in ion-based clocks, and the applicability of the approach to other alkaline-earth ions.
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All authors N Jayjong, M D K Lee, K J Arnold, M D Barrett
Fluid Dynamics
Thermodynamic Non-Uniformities Behind Incident and Reflected Shocks in a Single-Diaphragm Shock Tube
Touqeer Anwar Kashif, Janardhanraj Subburaj and Aamir Farooq
Shock tubes provide well-controlled high-temperature and high-pressure conditions for chemical kinetics studies, yet the region behind the reflected shock is seldom perfectly homogeneous. Axial and radial gradients arise from shock formation, attenuation, and the interaction of the reflected shock wave with the boundary layer, and these variations influence chemical kinetic measurements such as ignition delay time. The present study combines experimental diagnostics and numerical simulations to quantify these gradients in a single-diaphragm shock tube. A coupled RANS-LES framework implemented in CONVERGE CFD incorporates realistic diaphragm opening profiles and is validated using pressure histories and shock velocity profiles for argon, nitrogen, and carbon dioxide. The results show that incident shock attenuation strongly influences the thermodynamic state of the reflected-shocked region, with test gas-dependent differences: a nearly uniform core with modest axial gradients is maintained in argon, whereas substantial axial gradients due to reflected-shock and boundary-layer interactions is seen in nitrogen and carbon dioxide. The analysis provides a foundation for quantifying test-gas homogeneity in shock-tube experiments and potential extrapolation to improving interpretation of ignition data acquired under non-ideal flow conditions.
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Applied Physics · Cross-listed from cond-mat.mes-hall
Fast readout for large scale spin-based qubits
X. Luo, B. Bertrand, H. Niebojewski et al. (+3 more)
In this letter, we present fast readout of Pauli
spin blockade phenomena and interdot coupling tunability in a silicon double
quantum dot (DQD) fabricated using industry-compatible processes. The interdot couplings are tuned with a second self-aligned gate layer. The charge sensing and
spin readout are performed by using gate-based reflectometry techniques. The results pave the way for scalable fast readout of large-scale industry-standard manufactured Si
spin qubit arrays.
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All authors X. Luo, B. Bertrand, H. Niebojewski, F. Martins, C. Smith, T.-Y. Yang
Plasma Physics
Magnetohydrodynamics in turbulent dynamo regime: the stability problem
Michal Hnatič, Tomáš Lučivjanský, Lukáš Mižišin et al. (+2 more)
This paper investigates
stochastic solenoidal magnetohydrodynamics within the field-theoretic Martin-Siggia-Rose-De Dominicis-Janssen formalism, with a specific focus on the stability of the system when spatial mirror (parity)
symmetry is explicitly broken. Under helical forcing, the one-particle-irreducible
magnetic response function already at one loop contains a curl-type contribution that dominates the bare resistive term in the infrared limit, leading to exponential instability of the trivial state $\langle \mathbf{b} \rangle = \mathbf{0}$. We re-examine a stabilization mechanism proposed in [L. T. Adzhemyan, et al., Theor. Math. Phys. 72, 940-950 (1987)], in which the system evolves into a phase with a dynamically spontaneously broken rotational
symmetry and a generated mean
magnetic field $\langle \mathbf{b} \rangle = \mathbf{B}_0$. By deriving a self-consistency condition for $ \mathbf{B}_0$, we show that for any physically admissible (infrared) form of the pumping function, the model admits only a singular solution. We illustrate this with the standard power-law and "massive" pumping functions. We further show that previous claims of a finite $ \mathbf{B}_0$ arose from an inconsistent truncation of asymptotic expansions. We argue that a consistent physical resolution requires including a bare curl term in the
stochastic induction equation, which naturally arises from a parity-violating modification of Ohm's law. With this modification, stabilization of the system by spontaneous
symmetry breaking becomes a viable field-theoretic description of large-scale mean-field generation (turbulent dynamo) in helical turbulent magnetohydrodynamics.
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All authors Michal Hnatič, Tomáš Lučivjanský, Lukáš Mižišin, Yurii Molotkov, Andrei Ovsiannikov
Optics
Deep learning assisted inverse design of nonreciprocal multilayer photonic structures
Weiran Zhang, Hao Pan and Shubo Wang
Nonreciprocal structures play an important role in optical physics and applications. Conventional approaches for designing nonreciprocal optical structures rely heavily on extensive numerical simulation and parameter tuning, leading to high computational cost and low efficiency. Here, we apply deep learning to the design of nonreciprocal multilayer photonic structures. Three neural-network models-a forward neural network (FNN), an inverse design network (IDN), and a variational autoencoder (VAE)-are employed to learn the complex mapping between structural/material parameters and nonreciprocal spectral characteristics. We show that the FNN can rapidly and accurately predict the nonreciprocal electromagnetic response of a given structure, while the IDN can directly generate suitable structural parameters for target spectral responses. Both approaches substantially reduce computational cost and design time while improving nonreciprocal performance. Furthermore, the VAE can generate band-limited inverse design under practical performance constraints, facilitating efficient exploration of multiple feasible structures that meet different threshold requirements within specified frequency bands. Our work highlights the potential of deep learning for the advanced design of nonreciprocal optical structures and devices.
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Computational Physics · Cross-listed from cond-mat.mes-hall
Gauge transformation for pulse propagation and time ordered integrals
Adel Abbout
We investigate a gauge transformation based on the successive elimination of time-dependent onsite potentials at individual sites in finite or infinite systems. Our analysis shows that this transformation renormalizes the inward hoppings by a phase factor $e^{i \phi(t)}$ and the outward hoppings by $e^{-i \phi(t)}$. We further demonstrate how this procedure facilitates the reduction and simulation of pulse propagation in scattering systems, while significantly simplifying the time-ordered integrals involved in the time
evolution operator for time-dependent Schrodinger equation.
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Physics and Society
Planning for isolation? The role of urban form and function in shaping mobility in Brasilia
Andrew Renninger
Brasília offers a rare test of how urban form shapes experienced segregation. Built almost at once around modernist neighbourhood units, then expanded through planned satellites and informal peripheries, it lets us ask whether urban form turns mobility into mixing or into a more efficient engine of separation. We combine data on human mobility with urban morphometrics, amenities, road networks, along with enclosures and tessellations that capture segregation at the scales where access is structured: districts, neighbourhoods, blocks, and street-and-building
cells. We find that segregation intensifies as resolution sharpens, from 0.282 at the district scale to 0.545 at the block scale, indicating that Brasília looks most integrated at coarse units and most segregated where everyday encounters are actually organised. Mobility softens home segregation for most users, but not symmetrically: poorer groups travel farther, while affluent groups remain the most selectively exposed. civic cores and mid-rise, mixed-use areas are the least segregated morphotypes, yet they occupy only a sliver of the metropolis. Elsewhere, rich lakefront suburbs and dense poor settlements reach similarly high segregation through opposite spatial logics. Amenities predict lower segregation, while barriers and enclosed residential interiors predict higher segregation. Built form explains more of this pattern than visit volume alone in the segregation models: integration is less a property of residential design than of shared destinations and porous connections. Planned capitals can build order without building isolation if they distribute mixing space rather than sequestering it.
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Physics and Society
Technological Excellence Requires Human and Social Context
Karl Palmås, Mats Benner, Monica Billger et al. (+18 more)
Breakthrough technologies increasingly shape social institutions, economic systems, and political futures. Yet models of research excellence associated with such technologies often prioritize technical performance, scalability, and short-term innovation metrics while treating ethical, social, and cultural dimensions as secondary considerations. This perspective article argues that such separation is no longer tenable. We propose a broader understanding of excellence that combines technical rigor with ethical robustness, social intelligibility, and long-term relevance. The rapid emergence of generative and agentic artificial intelligence further underscores this argument. As technological systems increasingly operate through
language, interpretation, and normative
alignment, expertise traditionally cultivated in the humanities and social sciences becomes integral to the design, governance, and responsible deployment of such systems. Drawing on historical examples and contemporary research practices, this article examines five interconnected domains where the humanities and social sciences, treated as integrated dimensions of research practice, can strengthen technological development: (1) ethical, legal, and social integration in agenda-setting and research design; (2) plural and reflexive foresight practices that shape technological futures; (3) graduate education as a leverage point for cross-disciplinary literacy; (4) visualization and communication as epistemic and civic practices; and (5) institutional frameworks that move beyond rigid distinctions between basic and applied research. Across these dimensions, we propose practical strategies for
embedding interdisciplinary collaboration structurally rather than symbolically.
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All authors Karl Palmås, Mats Benner, Monica Billger, Ben Clarke, Raimund Feifel, Julia Fernandez-Rodriguez, Anna Foka, Juliette Griffié, Claes Gustafsson, Kerstin Hamilton, Johan Holmén, Kristina Lindström, Tobias Olofsson, Joana B. Pereira, Marisa Ponti, Julia Ravanis, Sviatlana Shashkova, Emma Sparr, Pontus Strimling, Fredrik Höök, Giovanni Volpe
Optics · Cross-listed from quant-ph
Experimental simulation of non-equilibrium quantum piston on a programmable photonic quantum computer
Govind Krishna, Rohan Yadgirkar, Balakrishnan Krishnakumar et al. (+6 more)
Quantum fluctuation relations provide a microscopic formulation of thermodynamics beyond
equilibrium, but experimentally accessing many-body
quantum work statistics remains an outstanding challenge. The
quantum piston constitutes a canonical model of boundary-driven nonequilibrium dynamics, where finite-time deformation of a confining potential generates non-adiabatic transitions, dissipation and irreversibility. Here we experimentally simulate the nonequilibrium dynamics of a two-
boson quantum piston on a programmable photonic
quantum computer. Using two indistinguishable
photons, we encode a truncated piston propagator through a quasi-
unitary embedding, with an ancilla mode representing leakage into higher-energy states outside the resolved
manifold. This architecture enables direct reconstruction of thermodynamic transition statistics for both expansion and compression protocols as functions of driving speed and final trap length. We observe the crossover from quasi-adiabatic to strongly non-adiabatic
evolution and show that bosonic interference restructures the resulting two-particle Fock-state populations and work distributions. The measured statistics are in close agreement with theoretical predictions and satisfy the Jarzynski equality across expansion and compression protocols for cyclic driving we further quantify irreversibility through dissipated work and state overlap. Our work identifies programmable photonic
quantum hardware as a powerful platform for simulating nonequilibrium
quantum thermodynamics and for experimentally resolving how indistinguishability and many-body interference shape
quantum work, dissipation and
entropy production.
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All authors Govind Krishna, Rohan Yadgirkar, Balakrishnan Krishnakumar, Andrea Cataldo, Ze-Sheng Xu, Johannes W. N. Los, Val Zwiller, Jun Gao, Ali W. Elshaari
Optics
Solid-state laser cooling of Yb3+-doped KY3F10 to 145 K
Luca Koldeweyh, Stefan Püschel, Zoe Liestmann et al. (+1 more)
We report
laser cooling of Yb3+-doped KY3F10 (Yb:KY3F10) driven by a 100-W, 1020-nm pump source. Despite pumping at a non-optimal wavelength, high-quality KY3F10
crystals doped with 3% and 7% Yb were cooled to 145 K and 151 K, respectively, in a double-pass pump configuration. These results establish Yb:KY3F10 as an attractive
laser-cooling medium competitive with Yb:YLF, the state-of-the-art
laser-cooling material for optical cryocoolers. The observed cooling performance and spectroscopic characteristics suggest that lower cryogenic temperatures may be achieved through pump-wavelength optimization, enhanced pump absorption, and reduced radiative heating.
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All authors Luca Koldeweyh, Stefan Püschel, Zoe Liestmann, Hiroki Tanaka
Optics · Cross-listed from quant-ph
Topological robustness of orbital angular momentum entanglement in stochastic channels
Tatjana Kleine, Pedro Ornelas, Cade Peters et al. (+5 more)
Orbital angular momentum (OAM)
entanglement gives access to multiple
qubit and high dimensional
Hilbert spaces, but is unfortunately susceptible to disturbance, decaying in real-world noisy channels. Here, we show there is an underlying
topology arising from OAM
entanglement that is robust to such channels, which we demonstrate using atmospheric
turbulence – exemplary of
stochastic or chaotic media. Using a
quantum channel with various
turbulence strengths, we find the OAM topological observable preserved even though the OAM itself is shown to be highly sensitive to the
turbulence. We show this is true for mixed states too, with the OAM
topology intact even as the purity of the state decreases due to decoherence. Our work offers a new perspective on OAM
entanglement preservation, and may easily be extended to other spatial bases, degrees of freedom, as well as complex channels, whether static or dynamic.
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All authors Tatjana Kleine, Pedro Ornelas, Cade Peters, Zhenyu Guo, Bereneice Sephton, Isaac Nape, Yijie Shen, Andrew Forbes
Optics · Cross-listed from quant-ph
Fundamental Limits of Non-Hermitian Sensing from Quantum Fisher Information
Jan Wiersig and Stefan Rotter
Exceptional points (EPs) exhibit strongly enhanced spectral responses and are therefore promising candidates for sensing applications. Whether these non-Hermitian degeneracies provide a genuine advantage in the
quantum regime has been the subject of ongoing debate. Here, we address this issue within a scattering-
matrix formalism for sensing with coherent light, which allows the
quantum Fisher information (QFI) to be evaluated directly from experimentally accessible scattering data without introducing additional noise channels beyond those inherent to the scattering process. We analyze both nondegenerate and degenerate scattering-
matrix poles, including EPs of arbitrary order, and show that the QFI per incoming
photon flux is governed by three key factors: the decay rate of the resonant mode, the strength of the spectral response associated with non-normality, and the adjustment between the scattering states and the information source. For spatially localized perturbations, this implies that the Fisher information is fully determined by the local density of states at the perturbation site. Within this framework, we demonstrate that EPs can enhance the QFI compared to isolated modes or diabolic points with identical decay rates, and that the QFI can be further increased by moving away from the EP toward parameter regimes where non-Hermitian linewidth splitting reduces the decay rate of one mode. We further show that sufficiently small additional internal losses do not alter this overall picture, thereby providing a unified and experimentally relevant perspective on the design of
quantum-limited non-Hermitian sensors.
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History and Philosophy of Physics · Cross-listed from quant-ph
Is the existence of unbounded operators a problem for quantum mechanics? In response to Carcassi, Calderon, and Aidala
Zhonghao Lu
In this paper I argue against Carcassi, Calderon, and Aidala's recent claim that the
Hilbert spaces are unphysical and should be replaced with the Schwartz spaces in
quantum mechanics, since
Hilbert spaces include states with infinite expectation values for certain observables. I also review and discuss issues regarding unbounded operators in
quantum mechanics raised by Streater and Wightman, Heathcote, and Lemos. I argue that the existence of infinite expectation values does not cause problems in
quantum mechanics. On the other hand, replacing the
Hilbert spaces with the Schwartz spaces would cause more issues, as it would exclude a class of meaningful
Hamiltonian evolutions. I also discuss the question in literature whether reformulating
quantum mechanics with essentially self-adjoint operators instead of self-adjoint operators may cause problems. I further analyse the hierarchies of the notions of "physicality" and possibility in fundamental physics, and suggest that "physicality" is a vague concept. Finally, I connect the problem raised by Carcassi, Calderon, and Aidala with the problem of the Hadamard condition in
quantum field theory.
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Geophysics
Monitoring of slopes, rock faces and masonry walls in a 19th century public park: the example of the Buttes Chaumont Park (Paris, France)
Marc Peruzzetto, Isabelle Halfon, Clara Lévy et al. (+6 more)
Developed on former gypsum quarries, the Buttes Chaumont Park is a 25-hectare geotechnical complex that is unique in the world. After three years of heavy work to create, in particular, an artificial cave, a lake and an island, the park opened in 1867 and has suffered gravitational hazards ever since (landslides, rockfalls and sinkholes). The BRGM has worked with the Paris City Council since 2021 to characterize the geological and geotechnical context, identify major gravitational hazards, and monitor the
evolution of instabilities in slopes and rock/masonry walls. In this context, the BRGM has proposed, defined and followed a geotechnical supervision scheme including four levels of monitoring: detailed quarterly site visits since March 2023, bimonthly tacheometric surveys (operating since December 2022), monthly manual gauges measurements (since January 2024), and automatic extensometers and temperatures measurements (since March 2024). The interpretation of the data allows to confirm and/or complement the gravitational hazard mapping that had been carried out in 2022. By analyzing the correlation between displacement measurements and meteorological conditions, we could also differentiate between seasonal/daily trends mainly associated with temperature variations, and displacements associated with gravitational processes. These results help mitigate risks in the Buttes Chaumont Park in its current state, and adapt works planned in the coming years to restore and secure the park.
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All authors Marc Peruzzetto, Isabelle Halfon, Clara Lévy, Florian Masson, Aurore Ramage, Gildas Noury, Daoud Benazzouz, Marina Kudla, Laurence Lejeune
Geophysics
Crustal Structure Imaging of Ghana from Single-Station Ambient Noise Autocorrelations and Earthquake Arrival Time Inversion
Hamzeh Mohammadigheymasi, Courage K. Letsa, Nasrin Tavakolizadeh et al. (+5 more)
The crustal architecture of southern Ghana remains inadequately resolved despite its tectonic significance and resource potential. Existing geological and geophysical studies provide only broad constraints on crustal composition, lacking the resolution to accurately define sediment-basement interfaces or intra-crustal stratigraphy. To address these limitations, we employ single-station ambient noise autocorrelation (SSANA) on continuous waveform data from the Ghana Digital Seismic Network (GHDSN). We extract P-wave reflectivity responses using a processing sequence that involves data pre-processing, Phase Cross-Correlation (PCC) for robust noise correlation, and phase-weighted stacking (PWS) of the derived autocorrelograms. This procedure yields a two-way travel-time (TWT) function representing the zero-offset P-wave reflection response beneath each station, enabling high-resolution imaging of the stratified crustal column. To facilitate depth conversion, we develop an enhanced one-dimensional crustal velocity model for the region. Using a compiled
dataset of local earthquake P- and S-wave arrival times from the GHDSN and an additional station in Cote d'Ivoire, we perform a joint inversion via a grid-search
algorithm to derive a regional 1D velocity structure. Our results provide new constraints on the depth and configuration of the Paleozoic basement beneath the Voltaian Basin, demonstrating the efficacy of ambient noise autocorrelation for crustal imaging in sparsely instrumented regions. We also present an updated seismicity catalog, relocated using the new velocity model, and analyze the spatial clustering of seismicity in southern Ghana. This study highlights the utility of passive seismic methods for elucidating crustal structure and evaluating resources in intraplate West Africa and analogous Precambrian terrains.
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All authors Hamzeh Mohammadigheymasi, Courage K. Letsa, Nasrin Tavakolizadeh, Zamir Khurshid, S. Mostafa Mousavi, Cyril D. Boateng, Paulina Amponsah, Martin Schimmel
Instrumentation and Detectors
High-Resolution Timing for Vertex-Reconstructed Muon-Spin Spectroscopy Using Plastic Scintillators and MuTRiG
Konrad Briggl, Maxime Lamotte, Marius Snella Köppel et al. (+12 more)
Vertex-reconstructed
muon-
spin spectroscopy (vx-{\mu}SR) based on silicon pixel detectors has recently demonstrated unprecedented lateral resolution and operation at
muon stop rates exceeding 400 kHz. However, the intrinsic timing resolution of current silicon pixel detector technology limits the accessible frequency range and restricts {\mu}SR measurements with fast relaxation rates. In this work, we report on the integration of plastic scintillator detectors (PSD) read out with the MuTRiG ASIC into the MuSiP vx-{\mu}SR spectrometer. This complements the spatial resolution achieved by using silicon pixel detectors with high-precision timing information for incoming
muons and decay positrons. We demonstrate stable operation of MuTRiG in
vacuum and achieve sub-300 ps time resolution after time-walk correction. Standard transverse-field {\mu}SR measurements on a SiO$_2$ sample confirm that the combined MuTRiG-PSD system resolves precession frequencies beyond 50 MHz, far exceeding the capabilities of silicon pixel detectors alone. These results establish a viable and scalable path towards high-rate, high-resolution {\mu}SR with both excellent spatial and temporal performance.
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All authors Konrad Briggl, Maxime Lamotte, Marius Snella Köppel, Jonas A. Krieger, Heiko Augustin, Niklaus Berger, Andrin Doll, Pascal Isenring, Hubertus Luetkens, Sebastian Mühle, Thomas Prokscha, Thomas Rudzki, André Schöning, Hans-Christian Schultz-Coulon, Zaher Salman
Atomic Physics
Quantum-logic spectroscopy of forbidden vibrational transitions in single nitrogen molecular ions
Aleksandr Shlykov, Meissa L. Diouf, Richard Karl et al. (+3 more)
Electric-dipole forbidden spectroscopic transitions in atoms form the basis of many advanced implementations of
quantum computers, atomic clocks and
quantum sensors. Coherently addressing such transitions in molecules which are among the most ubiquitous and versatile
quantum objects has remained a long-standing challenge owing to their complex energy-level structure. Here, we report the search, observation and coherent manipulation of electric-quadrupole rotational-vibrational transitions in single trapped molecules using a
quantum-logic-spectroscopy protocol. We identified individual hyperfine-Zeeman-rotational components of the fundamental vibrational transition of the nitrogen molecular ion, N$_2^+$, and performed coherent population transfer between energy levels. Our work opens up new perspectives for precision molecular spectroscopy, for high-fidelity
qubits encoded in the rotational-vibrational motion of molecules, for precise infrared molecular clocks and for searches for new physics
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All authors Aleksandr Shlykov, Meissa L. Diouf, Richard Karl, Mikolaj Roguski, Umesh C. Joshi, Stefan Willitsch
Plasma Physics · Cross-listed from astro-ph.SR
Neural Differential Equations for the Solar Dynamo
E. Illarionov, R. Stepanov, K. M. Kuzanyan et al. (+1 more)
Physical models aimed to reproduce basic features of the
solar sunspot cycle are typically based on the
solar dynamo mechanism. Usually qualitative arguments are used to define parameters of the model, among which a challenging component is the nonlinear form of quenching of the alpha-effect governing regeneration of the
magnetic field. We propose a novel approach, in which the functional form of the alpha-quenching is represented by a neural network model embedded into neural differential dynamo equations trained on observational data. For demonstration, we consider a low-mode dynamo model and find a wide set of alpha-quenching functions and corresponding dynamo numbers that provide an accurate fit to the average profile of the
solar cycle data given by sunspot numbers. Within this set, we observe a strong relationship between the dynamo number and the shape of the alpha-quenching function indicating that additional
magnetic field data or constraints are essential to unambiguously infer parameters of the dynamo model. In our opinion, the neural differential approach opens a new prospect for data-driven investigation of the closure problem in dynamo theory.
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All authors E. Illarionov, R. Stepanov, K. M. Kuzanyan, V. Kisielius
Chemical Physics
Towards Quantitative Reaction Dynamics of O3
Raidel Martin-Barrios, Abhirami Vijayakumar, Jingchun Wang et al. (+1 more)
The reaction dynamics of O(3P) + O2(3Sigma_g-) collisions in the O3(1A') electronic ground state is characterized on a high-level MRCI+Q/aug-cc-pVQZ potential energy surface represented as a reproducing kernel. For the atom exchange reactions involving the ^{16}O and ^{18}O isotopes as the atomic collision partner, associated with rates k6(T) and k8(T), respectively, a negative temperature-dependence of k(T), consistent with experiments was found. The absolute rates typically underestimate measured rates by 50 percent, depending on the experiment considered. For the ratio R(T) = k8(T)/k6(T), the measured T-dependence was found, including a cusp at lower temperatures. The differences between experiments and computations are primarily due to neglect of
quantum effects, primarily zero-point effects. For the atomization reaction, leading to 3O(3P), the rates is lower by approximately one order of magnitude compared with experiments, which is a clear improvement over simulations using previous potential energy surfaces computed with smaller basis sets. Non-adiabatic effects are deemed minor for the atom exchange reactions.
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All authors Raidel Martin-Barrios, Abhirami Vijayakumar, Jingchun Wang, Markus Meuwly
Chemical Physics · Cross-listed from cond-mat.mtrl-sci
First-Principles Electronegativity Scale from the Atomic Mean Inner Potential
Jin-Cheng Zheng
Electronegativity is a cornerstone of chemical intuition, essential for rationalizing bonding, reactivity, and material properties. However, prevailing scales remain empirically derived, often relying on parameterized models or composite physical quantities. In this work, we introduce a universal electronegativity scale founded on the atomic mean inner potential (AMIP), also known as the average Coulomb potential, a fundamental,
quantum-mechanical property accessible through both first-principles computation and electron-scattering experiments. Our scale, denoted $\chi_{\mathrm{AMIP},p}$, is an analytic function of just three ground-state atomic descriptors and carries explicit physical units. It demonstrates excellent agreement with established scales and successfully classifies bonding types across 358 compounds, including adherence to the metalloid “Si rule". Beyond replicating known trends, $\chi_{\mathrm{AMIP,1/2}}$ proves to be a powerful predictive tool, accurately determining Lewis acid strengths for over 14,000 coordination environments ($R^2=0.93$) and $\gamma$-ray annihilation spectral widths for 36 elements ($R^2=0.97$), outperforming previous methods. By linking electronegativity directly to a measurable
quantum property, this work provides a unified and predictive descriptor for electronic structure and chemical behavior across the periodic table.
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Plasma Physics
Existence domains of arbitrary amplitude nonlinear structures in two-electron temperature space plasmas. II. High-frequency electron-acoustic solitons
S. K. Maharaj, R. Bharuthram, S. V. Singh et al. (+1 more)
A three-component
plasma model composed of ions, cool electrons, and hot electrons is adopted to investigate the existence of large amplitude electron-acoustic
solitons not only for the model for which inertia and pressure are retained for all
plasma species which are assumed to be adiabatic but also neglecting inertial effects of the hot electrons. Using the Sagdeev potential formalism, the Mach number ranges supporting the existence of large amplitude electron-acoustic
solitons are presented. The limitations on the attainable amplitudes of electron-acoustic
solitons having negative potentials are attributed to a number of different physical reasons, such as the number density of either the cool electrons or hot electrons ceases to be real valued beyond the upper Mach number limit, or, alternatively, a negative potential double layer occurs. Electron-acoustic
solitons having positive potentials are found to be supported only if inertial effects of the hot electrons are retained and these are found to be limited only by positive potential double layers.
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All authors S. K. Maharaj, R. Bharuthram, S. V. Singh, G. S. Lakhina