Optics · Cross-listed from quant-ph
Wide-field mid- to long-wave infrared imaging with undetected photons
Vladimir Kornienko, Nathan Gemmell, Caiyi Liu et al. (+3 more)
Quantum imaging with undetected
photons (QIUP) allows an object to be probed at mid-infrared frequencies by only measuring interference in the visible range, thus leveraging silicon camera technology. We show that non-collinear phase-matching in a silver thiogallate (AgGaS$_2$)
crystal enables wide-field QIUP in the wavelength range of 6-10 $\mu$m (1670-1000 cm$^{-1}$). A combination of coherent detection and infrared
photons being “undetected” enables imaging at ${\sim}$100 times better than the background-limited infrared photodetection (BLIP) limit. At 8 $\mu$m, our images have over 8000 $\pm$ 100 resolvable elements with a 297 $\pm$ 5 $\mu$m resolution, and 10 s acquisition time. Our results pave the way to fast, background-noise-free, room-temperature, spectrally-selective mid-infrared imaging.
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All authors Vladimir Kornienko, Nathan Gemmell, Caiyi Liu, Asteria Chen, Chris Phillips, Rupert Oulton
Instrumentation and Detectors
Nanoscale silicon sensor - guided new insights into early metabolic response of Escherichia coli to ampicillin
Yingtao Yu, Victoria Nolan, Zheqiang Xu et al. (+4 more)
Antibiotic killing is often attributed to inhibition of specific cellular targets, yet metabolic processes can strongly influence drug efficacy. However, the relationship between metabolic responses and antibiotic lethality remains incompletely understood. Here, we employed silicon nanowire field-effect transistor (SiNWFET) sensors to monitor real-time metabolic responses of Escherichia coli to ampicillin (AMP). AMP treatment induced a biphasic extracellular pH signature, characterized by rapid acidification followed by alkalization. Metabolomic analyses revealed that the initial acidification resulted from organic acid secretion, whereas the subsequent alkalization was associated with altered amino acid metabolism and formate flux. Using metabolic and respiratory mutants, we found that these extracellular signatures reflected pathway-specific metabolic rewiring that predicted bacterial killing. AMP lethality strongly correlated with ATP dynamics and formate secretion: strains exhibiting larger AMP-induced ATP increases and greater formate secretion showed enhanced susceptibility. In contrast to literature, changes in NADH and NADPH levels did not support redox stress as the primary bacterial-killing mechanism. Together, our findings identify formate metabolism as a key pathway underlying the elevated ATP levels associated with AMP bactericidal activity. These results demonstrate that SiNWFET sensors provide a versatile label-free tool for probing antibiotic mechanisms, rapidly assessing bacterial susceptibility, and potentially guiding antimicrobial therapy development.
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All authors Yingtao Yu, Victoria Nolan, Zheqiang Xu, Allison Jones, George Alhoush, Zhen Zhang, Sanna Koskiniemi
Fluid Dynamics · Cross-listed from nlin.PS
Dissipation-driven champion solitons in one-dimensional shallow-water waves
Ashleigh Simonis, Sergey Nazarenko, Jalal Shatah et al. (+1 more)
In this paper, we identify a new mechanism for rogue wave formation in a shallow-water setting. We study a bidirectional shallow-water wave field in the context of the Kaup-Boussinesq equation, and introduce a weak high-wavenumber dissipative perturbation that breaks the underlying integrability of the system. In this setting, dominant
solitons grow through successive interactions with weaker, co-propagating
solitons, leading to the formation of a "champion
soliton" in each direction of propagation. This behaviour is in contrast to the general intuition that dissipation damps coherent structures, and instead shows that weak dissipation can induce their intensification. Moreover, we find that weak dissipation alone is not sufficient for champion
soliton formation; the presence of random waves plays a crucial role in the intensification process, catalysing the transfer of energy into dominant coherent structures. While champion
solitons have previously been studied in non-integrable systems, these works primarily consider perturbations introduced through modifications of the nonlinear terms (e.g., higher-order Korteweg-de Vries and Schrödinger-type models). In the present work, high-wavenumber dissipation provides a more physically natural perturbation, since such small-scale damping is a common feature in many systems.
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All authors Ashleigh Simonis, Sergey Nazarenko, Jalal Shatah, Yulin Pan
Computational Physics · Cross-listed from cs.LG
Green BOA: Determining the environmental break-even point for ML-based data compression
Caterina Doglioni, Thomas Elliott, Akshat Gupta et al. (+3 more)
We summarise the outcome of two summer internship projects based at the University of Manchester, focused on the break-even point in terms of environmental sustainability for ML-based data compression
algorithms. Using the example of a ML-based lossless compression
algorithm, we compare estimates for the carbon-equivalent of the infrastructure needed for ML training and inference with the carbon-equivalent savings from reduced disk storage requirements, and discuss their break-even point.
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All authors Caterina Doglioni, Thomas Elliott, Akshat Gupta, Hanzila Hussain, Sanjiban Sengupta, Zhengkai Sun
Computational Physics
Resonant state expansion for acoustic resonators. Part II. Scattering problem
Egor Domoratskii, Vladimir Igoshin, Nikolay Solodovchenko et al. (+4 more)
We develop a resonant-state expansion formulation for acoustic scattering by individual resonators. The scattered pressure and particle-velocity fields are expanded over the resonant states of the system, with excitation amplitudes determined by overlap integrals between the incident field and the resonant states over the resonator volume. Using the acoustic energy flux, we derive expressions for the extinction, scattering, and absorption cross-sections and show that the extinction spectrum can be resolved into contributions from individual resonant states. The formulation is first validated for a homogeneous two-dimensional cylinder, where it reproduces the analytical Mie-theory solution. We then consider a sectorally perturbed cylinder with coupled azimuthal modes and demonstrate agreement with finite-element simulations. Finally, we combine the
eigenvalue and scattering formulations for a material-programmed hard-wall annular metaatom and reproduce its scattering spectra and near fields. The developed framework provides a physically transparent modal approach to acoustic scattering by open resonators with reduced
symmetry and spatially structured material parameters.
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All authors Egor Domoratskii, Vladimir Igoshin, Nikolay Solodovchenko, Mingzhao Song, Yong Li, Mihail Petrov, Andrey Bogdanov
Geophysics
3-D numerical modelling of the feedback between deformation and thermal structure during subduction initiation for the French Lesser Antilles
E. Momoh, S. Tait and H. S. Bhat
We used 3-D thermomechanical modelling to investigate conditions during subduction-zone initiation and early thermal development with focus on the Lesser Antilles. Our model imposes a convergence velocity of 2 cm per year and incorporates heating caused by irreversible deformation of mantle and crustal rocks, using elasticity, creep, and non-associative plastic flow laws. Our results show that deformational heating before slab development is unexpectedly strong. After several million years, buckling and heating due to irreversible deformation create distinctive patterns of topography and surface heat flow that resemble present-day observations, despite the slab and subduction interface being incompletely developed. Within the Caribbean plate, plate buckling produces a high topographic ridge underlain by a large positive thermal anomaly of approximately 200 K, centred just below the Moho. The conductive thermal boundary layer transporting this heat to the surface thins from about 100 km to 10 km beneath the topographic maximum, allowing the ridge to rise above sea level. This thermal structure suggests the potential initiation of a volcanic arc approximately 180 km from the inter-plate contact. A hot zone at 30-50 km depth has pressures consistent with those inferred from Lesser Antilles primitive magmas and represents the most plausible location for partial melting of Caribbean mantle if volatiles are present. The thick Caribbean crust, approximately 20-25 km, is also heated sufficiently for possible silicic melt generation. The inferred lithospheric thickness of 50-100 km aligns with
tomography studies. Thus, subduction thermal structure is strongly influenced by several million years of initiation processes.
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Chemical Physics
Resonance Raman spectroscopy from ab initio Hagedorn wavepacket dynamics
Davide Barbiero, Léa Zupan and Jiří J. L. Vaníček
We present a practical, ab initio time-dependent method using Hagedorn wavepackets to simulate resonance Raman (RR) spectra of polyatomic molecules. Hagedorn functions—Gaussians multiplied by specific
polynomials—are used to represent RR initial and final states because these functions are exact solutions to the time-dependent Schrödinger equation for at-most-quadratic potentials and can be propagated at zero cost beyond that of propagating the guiding Gaussian. Using efficient recursive formulae to compute overlaps between Hagedorn wavepackets, we can evaluate RR excitation profiles for arbitrary spectral signals, such as fundamental, overtone, combination, and hot bands. We then construct the Stokes and anti-Stokes RR spectra from these profiles. We first validate the method in a two-dimensional displaced, distorted, and Duschinsky-rotated harmonic model against numerically exact split-operator calculations. Then, we apply the method to compute RR spectra of anthracene by performing dynamics on a 66-dimensional harmonic potential energy surface constructed from density functional theory calculations.
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Computational Physics
Resonant state expansion for acoustic resonators. Part I. Eigenvalue problem
Egor Domoratskii, Vladimir Igoshin, Nikolay Solodovchenko et al. (+4 more)
Resonant-state expansion (RSE) is a powerful modal framework for the perturbative analysis of open resonant systems, providing direct access to complex eigenfrequencies and eigenmodes. While RSE is well developed in electromagnetism, a comparably systematic formulation for acoustics remains less established. Here, we develop a general Green-function-based formalism for acoustic RSE and illustrate it for a class of two-dimensional acoustic resonators. Using the resonant states of an analytically solvable cylindrical reference system as a basis, we derive explicit perturbation
matrix elements for uniform, radial, and sectoral variations of density and compressibility, representing homogeneous tuning, graded profiles, and
symmetry-induced modal coupling. The resulting complex eigenfrequencies and eigenmodes are validated against exact analytical solutions and finite-element simulations, showing excellent quantitative agreement. The framework provides a systematic and physically transparent approach for analyzing perturbed open acoustic resonators and establishes a basis for resonant-state methods in acoustic metamaterials and non-Hermitian acoustics.
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All authors Egor Domoratskii, Vladimir Igoshin, Nikolay Solodovchenko, Mingzhao Song, Yong Li, Mihail Petrov, Andrey Bogdanov
Optics
Oscillator-driven broadband femtosecond transient microspectroscopy with supercontinuum probes generated in a photonic crystal fiber
Rikuto Fukuda, Kyosuke Kishihata, Ryo Man-nami et al. (+4 more)
We present an oscillator-driven femtosecond transient microspectroscopy system based on supercontinuum generation in a photonic
crystal fiber (PCF). The system operates at 80 MHz without pulse amplification, enabling high-sensitivity measurements with a detection sensitivity better than $10^{-4}$ while using low pulse energies suitable for microspectroscopy. Optimization of the PCF length ($\leq 50$ mm) suppresses dispersion-induced chirp, achieving nearly uniform temporal resolution below 100 fs across 450-900 nm. The high-repetition-rate operation allows rapid spectral acquisition and efficient noise reduction. The developed system provides micrometer-scale spatial resolution and supports both reflection and transmission configurations. Ultrafast carrier dynamics in multilayer and monolayer MoS$_2$ are successfully resolved, including spatially dependent relaxation within a single monolayer flake. These results demonstrate a versatile platform for probing local ultrafast dynamics in low-dimensional materials.
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All authors Rikuto Fukuda, Kyosuke Kishihata, Ryo Man-nami, Hiroaki Atsumi, Borja Cirera, DaeGwi Kim, Masahiro Shibuta
Computational Physics
Diagonalization of the Landau Hamiltonian with a Periodic Potential via a Galerkin Projection Method and Applications to Topological Band Properties
Rafael Antonio Lainez Reyes, Benjamin Stamm and Hans Peter Büchler
In this paper, we study the numerical computation of eigenfunctions of the Landau
Hamiltonian with a periodic potential. We propose a spectral method using the eigenfunctions of the Landau operator that allows us to numerically compute the band structure for potentials of different strengths, including the well-studied weak and strong potentials, and additionally systems in the intermediate regime. We then apply the method to simulations across the full range of coupling constants from weak to strong coupling and present an analysis of the band structure as a function of the potential strength.
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Optics
Full frame denoising for pyramid wavefront sensors
Noah Schwartz, Samuel Pinilla, Charlotte Z. Bond et al. (+3 more)
Adaptive optics systems operating under low-flux conditions face significant challenges, as
photon and detector noise in particular degrade wavefront measurements and ultimately limit correction performance. While pyramid wavefront sensors (PyWFSs) offer greater sensitivity than conventional wavefront sensors such as the Shack-Hartmann sensor in many operating regimes, obtaining accurate wavefront estimates under
photon-starved conditions remains a key challenge. We present a full-frame image denoising strategy for the PyWFS that exploits the nonlocal self-similarity of wavefront sensor image patches through FFT-accelerated patch grouping and global collaborative 3D wavelet filtering, applied directly to the raw PyWFS intensity frame prior to slope computation. Specifically, the method suppresses noise while preserving structural features required for accurate wavefront reconstruction. The approach is evaluated using end-to-end simulations of a VLT-scale SCAO system. The results show improved performance in low signal-to-noise regimes, with typical Strehl ratio gains of up to 12% and an increase in limiting magnitude of approximately 0.5 in median seeing conditions. Modal analysis indicates reduced variance across most controlled modes. The improved PSF quality enables a reduction in the FWHM and an enhanced contrast. These results demonstrate that image-domain denoising can improve the robustness of PyWFS-based AO systems and extend their operational range toward fainter guide
stars.
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All authors Noah Schwartz, Samuel Pinilla, Charlotte Z. Bond, Ben Buky, Gianfelice Cinque, Robert Rambo
Biological Physics
SoilWaterNow: Soil water nowcasting for mapping plant available water (PAW) across paddocks for improved on-farm decision-making
Yi Yu, Mikaela J. Tilse, Patrick Filippi et al. (+1 more)
Timely, paddock-scale estimates of plant-available water (PAW) can support crop management in water-limited grain systems. We present the Sydney Soil Water-Energy Balance (SWEB) model, a scalable, physically consistent modelling framework that integrates satellite and
climate data with soil properties to estimate crop evapotranspiration and root-zone soil moisture (RZSM) at daily, 30 m resolution. SWEB was validated nationally against different SM monitoring networks across Australia, which demonstrated robust performance across diverse grain-growing environments (correlation coefficients generally ranged from 0.70 to 0.85 for most regions). In future applications, mid-season PAW nowcasts could be combined with water-use-efficiency approaches to estimate water-limited yield potential and inform responsive management decisions, such as nitrogen fertiliser top-up recommendations.
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All authors Yi Yu, Mikaela J. Tilse, Patrick Filippi, Thomas F. A. Bishop
Plasma Physics
Effect of ion temperature on lunar photoelectron sheath
Trinesh Sana and Sanjay K. Mishra
Observations suggest that the
solar wind ions impinging on the lunar surface possess a finite temperature. The effect of ion temperature on the
plasma sheath over the lunar surface is investigated in this paper. To account for thermal effects, a thermal pressure term has been added to the ion-flow force equation. Quantitative estimation of sheath characteristics has been performed by solving the Poisson equation, accounting for photoelectrons,
solar wind electrons, and warm ions. Notably, the presence of warm ions within the sheath, i) changes the potential, field, sheath population density structures, ii) changes the sheath thickness, iii) reduces the photoelectron trapping, and iv) reduces
solar wind electron reflection, compared to cold ions. The effect is more prominent at high lunar latitudes, which in turn may significantly modulate the
dust dynamics.
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Instrumentation and Detectors
An Overview of Potential Medical Applications of Microwave Kinetic Inductance Detectors
Cáthal McAleer, Gary Donegan, Colm Bracken et al. (+4 more)
Microwave kinetic inductance detectors (MKIDs) have proven to be a versatile detector technology and are very promising for several applications in medical imaging. Deep imaging into human tissues often requires detectors with low background noise, high detection efficiency, broad wavelength sensitivity or single-pixel energy resolution. MKIDs offer a unique combination of valuable features for medical imaging but have so far not been discussed much for modern medical instrumentation. This represents an exciting opportunity to investigate the potentially powerful advantages MKIDs could offer for clinical studies in several areas. The most promising fields for MKIDs in medical imaging include fluorescence microscopy, near-infrared spectroscopy, energy-resolved medical X-ray imaging and synchrotron X-ray microscopy. We present the respective advantages MKIDs offer for these fields and compare them to current detector state-of-the-art.
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All authors Cáthal McAleer, Gary Donegan, Colm Bracken, Oisín Creaner, Mario De Lucia, Tom Ray, Gerhard Ulbricht
Atmospheric and Oceanic Physics
The impact of feature engineering and an optimisation framework for ocean colour machine learning
Edson Silva, Julien Brajard, Simon Cappe et al. (+2 more)
Machine learning (ML) is widely used for the development of ocean colour
algorithms, but most studies focus on model parameter training and hyperparameter tuning. The optimisation of the data that feeds the models - i.e., Feature Engineering (FE) - is not fully explored. We assess the impact of FE in ocean colour machine learning models and we propose an optimisation framework that includes seven sequenced levels of data transformation: i. band choice, ii. log scaling, iii. spectral shape normalisation, iv. index extraction, v. principal component analysis, vi. feature scaling, and vii. zero-to-one scaling. We demonstrate the application for Multi-layer perceptron, Support Vector Machines, and eXtreme Gradient Boosting Trees on Sentinel-3 OLCI observations in the Norwegian coastal waters. The models are trained to estimate Chlorophyll-a concentration [Chl-a] and Secchi disk depth (Zsd). Results show that accuracy is highly variable among FE found in six studies using Sentinel-3 OLCI and the ones that we optimise. The R range from 0.01 to 0.55 for [Chl-a] and from 0.15 to 0.68 for Zsd, where the optimised FE shows the top results. The ML models with optimised FE could also improve by two times the R and reduce up to 63% of the mean absolute error when compared to CHL_OC4ME and CHL_NN standard
algorithms. Nevertheless, no common optimised FE is found for all target variables and ML models, suggesting that FE optimisation is necessary for each application. Therefore, our proposed framework can be key for improving the accuracy of water quality monitoring in coastal waters.
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All authors Edson Silva, Julien Brajard, Simon Cappe, Lasse H. Pettersson, François Counillon
Optics
A Non-Hermitian Biorthogonal Encoding Paradigm for Physical-Layer Secure Computational Imaging
Xi-Hao Chen, Kan-Xu Jia, En-Rui Zhang et al. (+5 more)
The conventional paradigm of computational imaging, rooted in Hermitian systems, is fundamentally constrained by rigid orthogonal basis transformations, which bottleneck the balance between reconstruction fidelity, computational load, and physical-layer security. In this work, we propose a generalized secure computational imaging framework based on non-Hermitian biorthogonal
symmetry breaking. By mapping spatial information into a biorthogonal operator space, we establish an asymmetric sensing architecture governed by distinct left-basis $\langle\phi_{m}\vert{}$ and right-basis $\vert{}\psi_{n}\rangle$ modes, satisfying the biorthogonality relation $\langle\phi_{m}\vert{}\psi_{n}\rangle = \delta_{mn}$. Within this
manifold, precise tuning of the non-Hermitian parameter $\gamma$ establishes a physical-layer cryptographic gate, where high-fidelity
retrieval is exclusively enabled by matching the dual basis; any parameter mismatch triggers deterministic inter-modal crosstalk that effectively neutralizes unauthorized access. Notably, this architecture intrinsically supports direct, iteration-free image
retrieval across a wide range of sampling ratios, significantly reducing the computational overhead compared to conventional iterative reconstruction. We validate this framework on a single-pixel imaging platform, demonstrating a fundamental paradigm shift: by
embedding security directly into the measurement physics, we transform image
retrieval from a software-dependent task into a parameter-sensitive physical decryption process that ensures architecture-intrinsic confidentiality.
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All authors Xi-Hao Chen, Kan-Xu Jia, En-Rui Zhang, Yi-Zhu Zhang, Xin-Peng Wei, Bu-Ran Yu, Qian-Qian Bao, Shao-Ying Meng
Instrumentation and Detectors
Developing a Compact SWIR Imaging Spectrometer for CO2 and CH4 Retrieval Using Photonic Crystal Filters
Marijn Siemons, Brecht Simon, Irina Malysheva et al. (+1 more)
The need for atmospheric measurements with higher spatial and temporal resolution is driving the development of satellites and satellite constellations to complement existing flagship missions. We are developing an instrument concept based on photonic
crystal filters with tailored spectral transmission for trace gas
retrieval. These filters can be integrated directly with the detector module, enabling a highly compact system architecture. In this work, we present performance simulations for methane and carbon dioxide
retrieval in the 1.6 um SWIR band for a medium-resolution global coverage mission with an approximately 250 m spatial resolution and a 150 km swath. We furthermore introduce an improved
retrieval algorithm that substantially reduces
retrieval bias. These results demonstrate the potential of the proposed architecture for medium-resolution global greenhouse-gas mapping, with
retrieval performance comparable to state-of-the-art global mapping missions such as the planned CO2M mission at substantially finer spatial resolution. This measurement approach also inherently compresses the acquired spectral information, reducing the need for high downlink data rates. In the coming year, these filters will be fabricated by NIL Technology, followed by mechanical integration and experimental validation in a breadboard system.
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All authors Marijn Siemons, Brecht Simon, Irina Malysheva, Ralf Kohlhaas
Chemical Physics · Cross-listed from quant-ph
Resource-Efficient Bio-Molecular Docking on a NISQ-era Digital Quantum Computer
Tianqi Chen, Adrian M. Mak, Jianguo Li et al. (+3 more)
Molecular docking is a vital computational task in drug discovery, wherein the objective is to efficiently identify optimal binding poses between a ligand and a target receptor
protein. Due to the combinatorial explosion of possible binding configurations, docking of large and flexible molecules remains a computationally intensive problem, especially at scale. Early studies have revealed that the molecular docking can be re-cast as a maximum vertex-weighted clique problem (MVWCP) problem on a compatibility graph to be solved classically. In this work, we proposed a hybrid
quantum-classical approach for molecular docking leveraging the MVWCP formalism with a variational full-basis encoding (FBE) strategy, which enables efficient encoding of classical binary variables with Bloch sphere vectors. We further prove that a global minimizer of the FBE objective can always be chosen to be a pure product state, thereby providing a rigorous justification for its optimization using a
unitary variational
circuit. The molecular docking problem is first mapped to a cost
Hamiltonian that is minimized within a variational framework, optimized via a randomized imaginary time
evolution (ITE)-inspired warm start, and gradient-based techniques. Finally, we also executed the
circuit on an IBM
quantum computer, underlying the feasibility and of
quantum-assisted optimization for structure-based drug design and point towards the broader utility of advanced encoding techniques in
quantum optimization for computational biology.
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All authors Tianqi Chen, Adrian M. Mak, Jianguo Li, Jian Feng Kong, Chandra Verma, Sebastian Maurer-Stroh
Plasma Physics
Simulation of trapped non-neutral plasma dynamics with rotating wall compression
Luisa Riik and Oliver Boine-Frankenheim
A spectral macroparticle simulation scheme is used to model non-neutral
plasma dynamics in a Penning-Malmberg trap. This grid-free numerical scheme is well adapted to the specific geometry of trapped
plasmas, with varying longitudinal and transverse profiles in a cylindrical conducting pipe. The cutoff spectral harmonics provide control over the trade-off between accuracy and noise smoothing, which is especially important in the three-dimensional case. We demonstrate the ability of this scheme to obtain the dispersion relation of the
plasma modes from the inherent simulation noise, providing a valuable tool for understanding the
plasma's behavior. In the presence of a rotating wall drive, we show that the numerical scheme can reproduce the time
evolution of the driven eigenmodes, identify the onset of mode mixing with increasing drive amplitude and retrieve the compression rate dependency on the drive frequency, known from the weak drive regime of the rotating wall technique. To the authors' knowledge, such simulations have not been reported in the literature so far.
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Chemical Physics
Nuclear-Electronic Orbital Subsystem Density Functional Theory
Denis G. Artiukhin
We present a new computational approach based on
Nuclear-Electronic Orbital and Subsystem Density Functional Theory. The resulting NEO-sDFT methodology enables
quantum chemical calculations of large molecular systems composed of thousands of atoms while also describing selected
protons quantum mechanically. A key feature of the associated program implementation is its flexibility in assigning
quantum protons to subsystems, allowing different
embedding schemes to be employed within a unified framework. The accuracy of NEO-sDFT is assessed by computing water dimer interaction energies, which exhibit errors of only a few meV compared to reference
Nuclear-Electronic Orbital Density Functional Theory results. The favorable computational scaling of NEO-sDFT is further showcased through calculations on water clusters of increasing size, with up to 303
protons being treated
quantum mechanically. Our results demonstrate that NEO-sDFT is an accurate and efficient approach for incorporating
nuclear quantum effects into large-scale simulations, providing a foundation for future applications to
proton transfer processes in biochemical systems.
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Medical Physics
Simultaneous 3D co-registered perfusion and oxygenation with ULM, photoacoustic imaging, and a planar matrix array
Léa Davenet, Jacques Battaglia, Franck Lager et al. (+6 more)
Objective. Joint assessment of tissue oxygenation and microvascular perfusion could offer valuable insights into vascular function across a wide range of biomedical applications. Multispectral photoacoustic imaging enables the evaluation of blood oxygenation, while ultrasound localization microscopy provides sub-diffraction visualization of the microvasculature and blood perfusion. Here, we combine these two complementary modalities to simultaneously generate co-registered, volumetric maps of blood oxygenation and perfusion. Approach. Photoacoustic imaging and ultrasound localization microscopy are both ultrasound-based techniques. We developed an imaging platform that integrates the two modalities using a single planar ultrasonic
matrix array, a state-of-the-art array for 3D ultrasound localization microscopy. The bimodal platform was validated in vitro using vessel-mimicking phantoms, then in vivo in mice. Main results. In vitro bimodal images of tubes injected with contrast
agents demonstrated a coregistration accuracy of 20 $\mu$m and revealed complementary structural and functional information. Multispectral photoacoustic imaging achieved oxygen saturation measurements spanning the physiological range (60-95 %) with 5 % accuracy using only five optical wavelengths. In vivo imaging of healthy mouse tissues with known vascular anatomy further demonstrated the ability of the proposed platform to jointly characterize blood oxygenation and microvascular perfusion. Significance. This work experimentally validates a bimodal photoacoustic imaging-ultrasound localization microscopy approach using a planar ultrasound array. We characterized the functional imaging performance of this platform and identified limited-view artifacts inherent to this array configuration in photoacoustic imaging. These findings establish a foundation for adopting the platform in future studies of murine models and for advancing this promising bimodal approach.
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All authors Léa Davenet, Jacques Battaglia, Franck Lager, Pascal Dargent, Charlotte Lussey-Lepoutre, Bertrand Tavitian, Olivier Couture, Lori Bridal, Jérôme Gateau
Chemical Physics
Rare Fluctuations from Normally Hyperbolic Invariant Manifolds
Stephen Wiggins
Freidlin–Wentzell theory converts weak-noise large deviations into a
Hamiltonian variational problem. We study how a $k$-dimensional normally
hyperbolic invariant
manifold (NHIM) $N$ of the deterministic dynamics appears in this
Hamiltonian system. Its zero-momentum copy $N_0=N\times\{0\}$ is invariant, but the
Hamiltonian dynamics has $2k$ center directions near $N_0$: $k$ tangent to $N$ and $k$ conjugate covector directions. We construct the resulting local
symplectic geometry and show that fluctuation extremals approaching $N_0$ backward in time at the strong normal rate form an $n$-dimensional exact Lagrangian invariant
manifold carrying a single-valued action. A counterexample shows that a corresponding zero-energy section need not be normally
hyperbolic within $H_{\mathrm{FW}}^{-1}(0)$. We then consider reaction dynamics. If a parameter moves a deterministic trajectory toward a codimension-one reactivity boundary, the minimum Freidlin–Wentzell action required to reach the boundary is quadratic in the distance from the threshold parameter. Its coefficient is determined by the relative motion of trajectory and boundary and by how effectively the available noise acts transversely. This deterministic boundary is distinct from a noise-dependent
stochastic transition state or a committor surface. In a solvent–solute model, varying solvent mass moves the phase-space reactivity boundary while leaving the potential-energy surface fixed, changing the rare-event cost without changing the potential-energy barrier.
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Classical Physics · Cross-listed from cond-mat.mtrl-sci
Constitutive modelling of open-porous neo-Hookean solids
Ameya Rege
Open-porous materials exhibit pronounced compressibility, nonlinear densification, and power-law scaling of stiffness with density. In this work, we propose a thermodynamically consistent compressible neo-Hookean constitutive model for open-porous solids in which porosity serves as the primary governing variable. The strain-energy density is formulated to couple distortional elasticity of the solid skeleton with a volumetric response governed by deformation-induced porosity
evolution, including a bounded representation of pore collapse. The formulation introduces a minimal set of parameters, namely the initial porosity, intrinsic skeleton
moduli, and a scalar parameter controlling the onset of densification. A key feature of the model is a modified volumetric term in which the response is normalised by the current porosity, ensuring a physically consistent transition from a porous to a densified state without artificial stiffening. In the small-strain limit, the model recovers classical linear elasticity with effective
moduli that may be chosen either from homogenisation bounds, such as the Hashin-Shtrikman estimates, or from Gibson-Ashby-type power-law scaling to capture
topology-dependent behaviour. At finite strains, the formulation captures the characteristic nonlinear stiffening and convex stress-stretch response associated with progressive pore collapse. The proposed framework thus provides a compact, flexible, and extensible constitutive description that unifies effective-medium consistency with experimentally observed scaling behaviour, and is well suited for finite element implementation and multiscale modelling of highly compressible open-porous materials. The model is finally validated against available experimental data.
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Computational Physics · Cross-listed from gr-qc
Kerr Quasinormal Modes without Variable Separation: A Two-Dimensional Hyperboloidal Teukolsky Solver with Physics-Informed Neural Networks
Antonio Ferrer-Sánchez, Daniela D. Doneva, José D. Martín-Guerrero et al. (+4 more)
We use physics-informed neural networks (PINNs) to solve the gravitational quasinormal-mode (QNM)
eigenvalue problem for Kerr spacetime directly in the two-dimensional hyperboloidal formulation of the Teukolsky equation. This formulation does not require separation of variables and thus retains the coupled radial–angular structure. Such a scheme provides a prototype for calculating the QNMs of beyond-Kerr black holes for which the perturbation equations are non-separable. Sequences with increasing angular momentum are constructed, reaching close to the extremal limit. We focus on the fundamental modes $(\ell,m,n)=(2,0,0)$, $(2,1,0)$, $(2,2,0)$, $(3,3,0)$ and $(4,4,0)$, together with the first overtone $(2,2,1)$. Independent
benchmark evaluation shows that every reported real and imaginary frequency component remains below $0.5\%$ error, with a median deviation of $0.1\%$. This accuracy is maintained in the near-extremal regime, where the damping rate becomes small and the modes are longest-lived. The results establish a non-spectral numerical route to multidimensional black-hole perturbation eigenproblems which does not match the substantially higher precision of dedicated Kerr solvers but offers greater flexibility and requires less analytical pre-processing. Non-separable rotating backgrounds and coupled systems, such as gravitational–electromagnetic Kerr–Newman perturbations, are natural extensions of the same construction.
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All authors Antonio Ferrer-Sánchez, Daniela D. Doneva, José D. Martín-Guerrero, Stoytcho S. Yazadjiev, Roberto Ruiz de Austri-Bazan, Yolanda Vives-Gilabert, José A. Font
Applied Physics
Experimental Realization of Topological Surface Acoustic Wave Resonances under Surface Liquid Loading for Micro-volume sample Sensings
Bowei Wu, Tingfeng Ma, Hanbang Deng et al. (+1 more)
Surface acoustic wave (SAW) sensors, owing to their high operating frequencies, compatibility with planar micro-fabrication, and exceptional sensitivity to surface perturbations, are widely used in lab -on-a-chip and biomedical diagnostic applications. However, conventional SAW sensors operating in
liquid environments suffer from substantial energy dissipation, which markedly reduces their quality factors (Q factors) and limits sensing reliability. Here, we design and fabricate a topological SAW resonant sensor for surface
liquid loading by exploiting interference coupling between topological interface states and resonant cavities. The band structures are validated using a semi-analytical plane wave expansion-finite element method. The device requires only 0.04 uL of sample and enables concentration sensing of NaCl and glucose solutions, with sensitivities of up to 190 kHz/% for NaCl and 101.8 kHz% for glucose, respectively, and a concentration resolution of 0.01%. This work offers a potential technological route towards high-performance SAW biomedical chips for micro-volume sample analysis.
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All authors Bowei Wu, Tingfeng Ma, Hanbang Deng, Shuanghuizhi Li
Optics
Nonlinear tunnel oscillations of light in spherical Bragg resonators
Victor P. Ruban
A weakly nonlinear regime of radial tunneling is theoretically considered for a light wave in a spherical dielectric Bragg resonator containing a set of “shell” eigenmodes (both TE and TM) with different azimuthal numbers $l\geqslant 1$, which are concentrated near a defect of the Bragg structure, several layers away from the origin. Also, a single mixed radial mode with $l=1$ is located near the resonator center, either TM or TE. Nonlinearity of Kerr type in the main approximation is actual for the central mode only, while all the shell modes remain in the linear regime. The tunneling occurs between the central mode and the shell $l=1$ mode of the same
symmetry. Nontrivial part of the dynamics of optical field is described by a
Hamiltonian system of ordinary differential equations for complex vectors ${\bf C}_{1}(t)$ and ${\bf C}_{2}(t)$, which determine the magnitude and spatial orientation of the wave structures at the center and at the shell, respectively. Depending on “asymmetry parameter” of tunnel coupling, the system demonstrates different variants of nonlinear behavior.
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Chemical Physics
A Comparative Study of Coherent and Action-Detected 2D Electronic Spectroscopies of a Multichromophore Photosynthetic System
Edoardo Amarotti, Ajeet Kumar, Luca Bolzonello et al. (+3 more)
Coherent two-dimensional electronic spectroscopy (C-2DES) is a powerful tool for resolving excitonic structure and dynamics in light-harvesting complexes with dense energy-level
manifolds. In contrast, action-detected 2DES has seen limited use on such systems, and its capacity to reveal electronic structure and dynamics remains unclear. Here we compare C-2DES and fluorescence-detected 2DES (F-2DES) on the major plant light-harvesting complex (LHCII) at 78 K. C-2DES resolves excitonic features and their spectral
evolution, mapping energy-transfer pathways. F-2DES shows strong cross-peaks, but these are largely time-invariant and dominated by incoherent mixing, obscuring the dynamics. C-2DES is therefore preferred for resolving ultrafast energy transfer in light-harvesting complexes and other large interacting networks. Combined, the two measurements directly quantify the suppression of population dynamics by incoherent mixing, confirming that nearly the entire LHCII trimer network contributes. We also identify pulse-shaper nonlinearities in F-2DES as spurious features, highlighting the need for rigorous artifact suppression.
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All authors Edoardo Amarotti, Ajeet Kumar, Luca Bolzonello, David Bina, Tõnu Pullerits, Donatas Zigmantas
Chemical Physics
Iterative Projection-Based Embedding Scheme Combined with Variational Quantum Eigensolver
Hongseok Choi, Kyungmin Kim and Young Min Rhee
Quantum embedding methods offer a promising route to extend
quantum chemical calculations to large multiscale systems by treating a chemically important subsystem at a high level of theory while describing its surrounding environment at an affordable level. The methods are also quite relevant for
quantum computing approaches based on hardware with limited resources. Here, we present an iterative projection-based
embedding framework combined with VQE, in which the environment density is allowed to respond self-consistently to the refined electronic structure of the embedded subsystem described by VQE. Unlike conventional one-shot approaches where the environment remains frozen after the initial orbital optimization, the proposed iterative scheme alternates between the VQE-level treatment of the subsystem and a mean-field-level refinement of the environment until mutual self-consistency is achieved. The convergence behavior of the scheme is first examined using several small test systems. Its practical applicability is then demonstrated with a composite system with a CH2NH molecule sandwiched by two benzene rings, with the C=N dihedral angle rotating from 0 to 90 deg. The iterative procedure consistently converges within ~10 iteration steps across all tested geometries, yielding energies below the conventional one-shot
embedding results. The converged results well reproduce the fully correlated reference energy employing the same active space, and the resulting potential energy surface with respect to the dihedral rotation is also in good agreement with the reference one. These results demonstrate that our iterative
embedding framework is numerically robust and physically sound, yielding a self-consistent and reliable treatment of inter-subsystem correlation. We expect that its formulation will be particularly compatible with the emerging paradigm of
quantum-classical hybrid computing.
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Optics
Cavity-Enhanced Activation of Radiatively Suppressed Light-Hole Exciton Emission in Colloidal Nanoplatelets
Komal Sharma, Riya Dutta, Prathmesh Deshmukh et al. (+2 more)
Light-hole (LH)
excitons provide access to well-defined polarization and
spin degrees of freedom that are central to
quantum photonics and
chiral light-matter interactions. Achieving LH emission is challenging because LH states are energetically unfavoured and typically relax non-radiatively. Existing strategies to access LH
excitons rely on modifying the electronic band structure through strain, shape anisotropy, or piezoelectric fields, approaches that are material-specific and offer limited post-synthesis tunability. Here we demonstrate an all-photonic route to activate LH
exciton emission in colloidal CdSe-CdS nanoplatelets (NPLs) using a distributed Bragg reflector (DBR) cavity, without altering the underlying band structure. In the absence of a cavity mode, the system exhibits amplified spontaneous emission from heavy-hole (HH) states without detectable LH emission at low excitation powers. By spectrally matching a cavity resonance to the LH
exciton, cavity-coupled LH emission emerges at significantly lower excitation powers. Temperature-dependent spectroscopy reveals reversible switching between LH- and HH-coupled emission through
exciton-cavity detuning, while polarization-resolved and spectrally resolved time-resolved photoluminescence measurements provide independent evidence distinguishing the cavity-coupled LH and HH emission channels. These findings establish cavity engineering as a general materials-level approach for accessing radiatively suppressed optical states.
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All authors Komal Sharma, Riya Dutta, Prathmesh Deshmukh, Vinod M.Menon, Jaydeep K. Basu
Geophysics
Co-seismic surface fault displacement captured in videos: image tracking across three earthquakes
Shiro Hirano
Surface displacements, including co-seismic fault slip, have occasionally been captured by closed-
circuit television (CCTV) cameras. Such
video recordings may provide information unavailable from seismometers located away from the fault. We analyzed
videos of surface displacement from three earthquakes—the 2018 Hualien earthquake, the 2025 Mandalay earthquake, and the 2026 Kumamoto earthquake—using a unified methodology. We removed the effects of strong ground motion by aligning each frame so that reference regions in the image remained fixed. This analysis enables the temporal
evolution and, in particular, the duration of surface displacement to be estimated. Although the three earthquakes ranged from $M_\mathrm{w}$6.4 to $M_\mathrm{w}$7.7, the tracked motion lasted approximately 2 s in all three cases; in the Hualien case, the motion included compression of the ground rather than fault slip alone. Comparison with field surveys indicates that the maximum velocity was on the order of 1 m/s in each case. The 2026 Kumamoto earthquake, however, exhibited a more complex velocity history than the other two events. The three earthquakes involved different mechanisms of surface fault displacement, suggesting that these differences may also influence the complexity of the displacement time histories.
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