Optics
Twist Engineering for Reconfigurable Optical and Optoelectronic Devices
Gang Huang, Annan Helian, Mengting Jiang et al. (+12 more)
Reconfigurable optical and optoelectronic devices require compact tuning mechanisms capable of reshaping electronic, excitonic, polaritonic, and photonic responses without rebuilding the underlying nanostructure. Against this backdrop, twist has emerged as a powerful
geometric degree of freedom that reconfigures interlayer coupling, momentum matching,
symmetry, radiation channels, and
chiral response by simply rotating adjacent two-dimensional layers or photonic
lattices. In this Review, we survey twist-engineered optical and optoelectronic devices spanning van der Waals materials and photonic platforms. We first review the current landscape of twist-angle metrology, classifying existing characterization approaches into three complementary categories: direct structural imaging, methods based on moiré periodicity and morphological features, and techniques that infer the twist angle from spectroscopic or electronic responses. We then survey the principal technological routes for twist-angle control, including deterministic transfer and growth strategies, atomic force microscopy (AFM)-assisted manipulation,
quantum twisting microscopy (QTM), microelectromechanical systems (MEMS), and emerging non-contact approaches, highlighting their respective capabilities, limitations, and prospects for programmable and scalable moiré photonic platforms. Finally, we discuss the future
evolution of twist engineering from the fabrication of individual twisted structures toward dynamically reconfigurable, feedback-controlled, and manufacturable photonic systems. We further highlight MEMS-based rotation, piezoelectric actuation, and micro-
LiDAR as representative enabling technologies and emerging applications within this broader landscape.
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All authors Gang Huang, Annan Helian, Mengting Jiang, Chi Wang, Yu Xing, Mayank Joshi, Jae Yeong Lee, Jiang Wang, Syed M Assad, Ping Koy Lam, Qiushi Liu, Lin Wu, Young-Wook Cho, Yuan Ma, Xuezhi Ma
Instrumentation and Detectors
Traceable In Situ Microwave Power Measurement at the Cryogenic Device Plane in a Dilution Refrigerator
Paolo Panetta, Andrea Celotto, Alessandro Alocco et al. (+7 more)
Accurate knowledge of the microwave power delivered to a cryogenic device under test (DUT) is essential for the characterization and operation of superconducting
quantum circuits. However, this information is difficult to obtain inside dilution refrigerators because of distributed attenuation, impedance mismatch, switch-path repeatability, and temperature-dependent microwave components. This paper presents an in situ measurement method for RF power at the cryogenic device plane. The method uses a custom variable temperature stage (VTS) as a cryogenic thermal-transfer element. The TVS is alternately heated by a four-wire DC heater and by microwave power dissipated in a 20 dB pass-through attenuator. By fitting the thermal transients and comparing the corresponding steady-state temperatures, the absorbed microwave power is inferred from a directly measured DC electrical power through an AC/DC substitution procedure. The finite reflection and transmission of the attenuator are then accounted for by cryogenic two-port scattering-parameter measurements based on a switch-assisted Short–Open–Load–Reciprocal calibration, so that the result is referred to the DUT reference plane. The system is demonstrated in a dilution refrigerator with powers between -43 and -58 dBm at the DUT input plane. The demonstrated relative standard uncertainty ranges from about 2% at -43.9 dBm to about 40% at -57.6 dBm. The proposed approach combines thermal RF power transfer, cryogenic S-parameter correction, and uncertainty evaluation in a measurement architecture compatible with
quantum-device experiments, providing a practical route toward traceable microwave-power calibration at millikelvin stages.
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All authors Paolo Panetta, Andrea Celotto, Alessandro Alocco, Bernardo Galvano, Luca Fasolo, Emanuele Palumbo, Luca Callegaro, Luca Oberto, Patrizia Livreri, Emanuele Enrico
Geophysics
An Extension to the Procedure for Developing Uncertainty-Consistent Shear Wave Velocity Profiles from Inversion of Experimental Surface Wave Dispersion Data
Joseph P. Vantassel and Brady R. Cox
Measurements of shear wave velocity (Vs) with uncertainty are critical for site-specific probabilistic seismic hazard studies. However, rigorously quantifying the uncertainty in Vs over large enough areas and great enough depths remains challenging. In 2021, Vantassel and Cox (i.e., VC21) proposed a procedure for developing suites of Vs profiles from surface wave testing whose uncertainty were consistent with the experimental dispersion data's uncertainty. The VC21 procedure was a significant step forward, however, it requires a full dispersion data
matrix to compute inter-wavelength phase velocity correlations. While applicable to many practical cases, VC21 could not be applied to the case where multiple surface wave arrays of different sizes were deployed at a site as a means of developing broadband dispersion data and deeper Vs profiles. In response, this work extends the VC21 procedure using two possible approaches for estimating a full dispersion data
matrix. Approach 1 uses a selection of theoretical dispersion curves from an initial, traditional surface wave inversion. Approach 2 estimates the full data
matrix by combining pieces of the data
matrix obtained from the experimental dispersion measurements. Both approaches are evaluated using two synthetic
datasets; one relatively-simple, three-layered model and one more-complex, five-layered model. Approach 1 and Approach 2 were able to reasonably estimate the true correlation
matrix and recover uncertainty-consistent Vs profiles similar to the true distribution of Vs. While the uncertainty of the recovered Vs profiles were higher than is often assumed, the engineering proxies computed from those Vs profiles, namely the time averaged shear wave velocity in upper 30 m and the fundamental site period, showed substantially less uncertainty indicating the Vs profiles, while uncertain, are effective at capturing a site's ...
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Instrumentation and Detectors
Influence of compaction pressure on the impedance of Gadolinium Doped Ceria electrolytes for IT-SOFCs
Renato A. N. de Oliveira, Celeste Z.A. Aquino, Magna Monteiro Schaerer et al. (+15 more)
Gadolinium doped ceria (GDC) is one promising oxygen-ion conducting ceramic electrolyte for intermediate-temperature solid
oxide fuel
cells (IT-SOFCs), due to its high ionic conductivity at reduced operating temperatures, favorable defect chemistry, and compatibility with a broad range of electrode materials [1,2]. Despite extensive understanding of its intrinsic ion transport mechanisms, the influence of ceramic processing parameters on the effective electrical behavior of polycrystalline GDC electrolytes remains an active topic for investigation [3-5]. In particular, processing steps that govern green body formation and sintering can strongly affect microstructural features such as density, grain size, grain boundary character, and residual porosity, which in turn determine the macroscopic conductivity [4-6]. In this work, dense GDC ceramic pellets were fabricated under systematically varied isostatic compaction pressures ranging from 49 to 140 MPa, followed by sintering at 1350 C for four hours under identical thermal conditions. Platinum electrodes were deposited on both sides of the pellets by electron-beam deposition, and the electrical properties were characterized by electrochemical impedance spectroscopy (EIS) over a wide temperature range. The results demonstrate a dependence of the impedance with respect to compaction pressure.
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All authors Renato A. N. de Oliveira, Celeste Z.A. Aquino, Magna Monteiro Schaerer, Rafael Galiza Yoshimura, Liliana Mogni, Maurico Arce, Diego G. Lamas, Lucia Toscani, Maria Belén Arcentales Vera, Esteban Elvis Asto Ramos, Marcia Carvalho de Abreu Fantini, Taofeeq Oladayo Bello, Tereza da Silva Martins, Danilo Waismann Losito, James Moraes de Almeida, Valeria Spolon Marangoni, Leopoldo Suescunand, Santiago Figueroa
Applied Physics
Are gate-all-around 2D CFETs the optimal architecture for the A2 node and beyond?
Fengben Xi, Gautam Gaddemane, Anshul Gupta et al. (+15 more)
As logic scaling enters the angstrom era, vertically stacked complementary field-effect transistors (CFETs) based on atomically thin two-dimensional (2D)
semiconductors offer a potential route to extend device scaling beyond the A2 node. Here, we develop an A2-oriented 2D CFET integration flow with a CPP of 36 nm and Lg of 10 nm and present initial demonstrations of several key process modules. Despite their atomically thin channels, 2D GAA CFETs do not provide a contacted poly pitch scaling advantage over Si GAA CFETs at the A2 node, because contact formation constraints impose a similar minimum CPP of 36 nm. We also combine a critical assessment with a multiscale power-performance-area (PPA) evaluation framework spanning
quantum transport simulations, compact-model generation, A2-targeted 2D CFET gate-all-around (GAA) integration-flow definition, parasitic extraction and
circuit-level benchmarking. Our analysis, however, shows that the expected benefits of 2D GAA CFETs are strongly constrained by non-idealities, in particular high contact resistance and dominant layout-induced parasitic capacitances. Although architectural optimization can improve the Ieff/Ceff ratio, the associated rise in absolute capacitance limits
circuit-level gains. Meaningful progress will require co-optimization of contacts, transport and parasitics, together with 2D-specific CFET architectures.
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All authors Fengben Xi, Gautam Gaddemane, Anshul Gupta, Sheng Yang, Aryan Afzalian, Quentin Smets, Maarten Van de Put, Kaustuv Banerjee, Tom Schram, Devin Verreck, Ward Janssens, Juergen Boemmels, Xiangyu Wu, Thomas Chiarella, Jérôme Mitard, Gouri Sankar Kar, Geert Hellings, Cesar Javier Lockhart de la Rosa
Applied Physics
High-frequency magnetotransport in LaMnO3 samples synthesized by microwave irradiation versus conventional heating
Y. H. Lee, M. Manikandan and R. Mahendiran
Magnetoresistance of hole-doped LaMnO3 at frequencies above a few MHz has been seldom reported compared to numerous studies on magnetoresistance measured at direct current. Here, we contrast the high-frequency magnetoresistance in the frequency range f = 0.9-3 GHz in polycrystalline LaMnO3 (LMO) synthesized by microwave irradiation of
oxide precursors in a microwave furnace (MW-LMO) and by conventional heating (CH-LMO) in an electrical furnace. The structure at room temperature changed from orthorhombic in CH-LMO to rhombohedral in MW-LMO. A combination of magnetization and resistivity studies suggest that the CH-LMO sample is a canted
antiferromagnetic insulator below 140 K but the MW-LMO is a
ferromagnetic metal with T_C = 240 K. While the high-frequency resistance of the CH-LMO sample at 300 K decreases gradually with increasing strength of the applied dc
magnetic field for all f, a peak appears at H = H_r larger than 0 gauss when f equal or greater than 1.4 GHz in the MW-LMO sample and H_r increases linearly with f. We attribute the observed features in the high-frequency magnetoresistance of MW-LMO to current-driven resonant excitation of
spins in the paramagnetic state. Its absence in the CH-LMO sample highlights the need for an optimum hole density to observe this effect.
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Plasma Physics
On the transition to large fluxes and access to second stability in gyrokinetic simulations of electromagnetic turbulence in STEP
Daniel Kennedy, Yujia Zhang, Toby Adkins et al. (+6 more)
This work investigates the nonlinear transition to large heat fluxes observed in local gyrokinetic simulations of electromagnetic
turbulence in STEP. Using the stress-balance framework of Zhang et al. (arXiv:2606.04616, arXiv:2607.11789), we confirm that the onset of extreme transport correlates with a critical value of $q^{2}\beta_{e}$, where $q$ is the safety factor and $\beta_{e}$ is the ratio of electron thermal pressure to
magnetic pressure, and relate this to a limit on the poloidal beta $\beta_{\mathrm{pol}}$. Crucially, this critical value lies below any relevant linear stability limit in the ($q$, $\beta_{e}$) space (e.g., the onset of ideal or kinetic ballooning modes). Using an extensive set of nonlinear gyrokinetic simulations, we demonstrate that the transition to large fluxes in STEP is governed by a balance between the electrostatic and
magnetic-flutter stresses. We argue, and also show numerically, that larger-major-radius tokamaks reach the electromagnetic non-zonal regime at lower $\beta_{e}$, making this MHD-controlled saturation limit more accessible in reactor-scale devices than in small spherical tokamaks. We also demonstrate that access to a second-stable regime enables re-saturation at larger values of $\beta^{\prime}$. We further show that the ideal ballooning mode (IBM) threshold serves as a useful proxy for delineating this second-stable region and also as a qualitative guide for the onset of large fluxes. These results provide a predictive framework for identifying no-go zone predictions from local gyrokinetics and offer new insight into the electromagnetic saturation physics relevant to STEP and other high-$\beta_{e}$ devices.
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All authors Daniel Kennedy, Yujia Zhang, Toby Adkins, Plamen Ivanov, Francis Casson, Harry Dudding, Bhavin Patel, Colin Roach, Howard Wilson
Chemical Physics · Cross-listed from quant-ph
Entanglement and Optical Nonreciprocity in spontaneous Raman Scattering
Frank Schlawin
Inelastic light scattering is a central tool for sample characterization and label-free imaging across the physical and life sciences. Recent work has suggested that scattered light can also exhibit nonclassical correlations. Here, we develop a microscopic theory of Raman scattering that connects naturally to established descriptions of entangled-
photon generation in three- and four-wave mixing, while capturing essential differences arising from the resonant, dissipative character of Raman scattering. Using a cumulant-expansion approach, we analyze the
entanglement structure of the scattered sidebands and identify signatures that distinguish Raman-mediated correlations from those generated in conventional off-resonant nonlinear wave mixing. In particular, we show that Raman scattering induces
chiral couplings between Stokes and anti-Stokes sidebands, leading to nonreciprocal amplification of coherent seed fields. These results establish a theoretical framework for Raman-based
quantum photonic protocols and suggest routes toward
quantum-enhanced Raman spectroscopy and imaging.
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Physics and Society · Cross-listed from q-bio.PE
Contrasting statistical patterns in melodic and molecular evolution reveal distinctive constraints in a culturally evolving system
John M McBride and W Tecumseh Fitch
Evolved sequences can be used to infer the rules of
evolution. Orally transmitted folk melodies are evolved sequences whose similarity to
protein sequences (one-dimensional, drawn from a limited alphabet) invites application of bioinformatics methods to study cultural
evolution. A major obstacle is that melodies encode rhythm, which breaks some assumptions of standard sequence-
alignment algorithms. We develop a rhythm-aware
alignment method and apply it to \num{40000} Irish dance tune variants, enabling the first large-scale automated melodic
alignment. Four canonical bioinformatics analyses – mutability, substitution
matrices, positional conservation, and covariance – reveal patterns distinct from those of molecular
evolution, revealing the forces that shape each domain: biochemical and biophysical constraints for
proteins;
memory, motor, and social biases for melodies. Together the results show that bioinformatics provides a powerful framework – conceptual as much as algorithmic – for studying cultural
evolution. Although the cultural transmission of music has been discussed for centuries, here we show how to analyze it at large scale.
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Optics
Collective-State Preparation in a Subwavelength Triangular Trimer Using SUPER Excitation
Thomas Nunner, Johannes Kerber, Helmut Ritsch et al. (+1 more)
The Swing-UP of
quantum EmitteR population (SUPER) scheme has recently been proposed as a deterministic method for the preparation of collective radiative states in two strongly dipole-coupled
quantum emitters (Phys. Rev. Res. 8, 013179 (2026)). Here, we apply this approach to an equilateral subwavelength triangular trimer of dipole-coupled two-level
quantum emitters (QEs), loosely inspired by biological light-harvesting ring geometries, and demonstrate that tailored, time-overlapping, red-detuned ultrashort SUPER pulses can selectively prepare collective states in a $C_3$-symmetric system, including energetically degenerate eigenstates that are resolved through site-dependent optical phases. We find that both the state selectivity and the preparation efficiency depend strongly on the inter-emitter spacing. In particular, at deep-subwavelength separations, the symmetric collective state can be deterministically prepared with near-unity efficiency (approximately $94\%$), whereas the inversion efficiency and state selectivity are significantly lower at larger inter-emitter separations. Furthermore, this state preparation technique inherits a certain degree of robustness against reasonable static position imperfections and on-site frequency inhomogeneities of the individual QEs. Our results demonstrate that deep-subwavelength triangular trimers and, more broadly, highly compact ring geometries are excellent candidates for the deterministic preparation of collective radiative states via SUPER excitation. These predictions could be realized with solid-state emitters and molecules. Our findings offer a route toward the direct probing of the `pure' electromagnetic layer of interaction in biological and bio-inspired synthetic nanophotonic ring configurations, with possible relevance in photonics,
quantum information processing, and metrology.
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All authors Thomas Nunner, Johannes Kerber, Helmut Ritsch, Arpita Pal
Instrumentation and Detectors · Cross-listed from quant-ph
Quantum metrology with undetected mid-infrared photons for applied non-destructive testing
Paul Gattinger, Andreas W. Schell, Maja Buchegger et al. (+2 more)
Metrology with undetected
photons is an emerging technique that leverages
quantum effects and
photon correlations (
entanglement) to retrieve valuable information in a target spectral range (e.g., mid-infrared, mid-IR) using measurements in an easily accessible domain (e.g., visible, near-IR). The underlying
quantum process of spontaneous parametric down-conversion (SPDC) is utilized to generate non-degenerate correlated signal and idler
photons to serve as detection and probing
photons, respectively. Sensing with undetected
photons enables important advantages, such as ultra-low probe powers, room-temperature operation, and shot-noise-limited detection. In this contribution, we apply a
quantum nonlinear interferometer based on an SPDC source to perform applied mid-IR spectroscopy, mid-IR microscopy, and mid-IR optical coherence
tomography (OCT) as among the most promising techniques for
quantum-based routine non-destructive testing. Moreover, we characterize the system,
benchmark it against classical systems, and provide a prospective outlook for this new technology.
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All authors Paul Gattinger, Andreas W. Schell, Maja Buchegger, Markus Brandstetter, Ivan Zorin
Chemical Physics
Core-excited and shape-type resonances in the micro-solvated Uracil: A CASSCF study
Sneha Arora and Achintya Kumar Dutta
Electronic resonances play an important role in electron attachment-induced processes in biomolecules, and their properties can be significantly influenced by the local molecular environment. Here, we investigate the effect of amino acid micro-solvation on the uracil resonances by employing uracil-glycine as a model system. The resonance spectrum of the uracil-glycine complex consists of four {\pi}-type shape resonances and three core-excited resonances, including an additional glycine-centered resonance, as characterized using the CASSCF/Resonance via Padé (RVP) methodology. Comparison with isolated uracil and the uracil(ghostGly) model shows that explicit interaction with glycine stabilizes both the shape and core-excited resonances by lowering their energies and increasing their lifetimes, while the ghost calculations demonstrate that basis-set extension alone cannot account for the observed stabilization. The core-excited resonances exhibit states that retain non-negligible lifetimes despite their much higher energy, suggesting that they may play an important role in electron-induced dissociation pathways. Overall, the present results demonstrate that amino acid micro-solvation significantly modifies the resonance landscape of uracil, highlighting the importance of explicitly accounting for local biomolecular interactions in theoretical studies of electron attachment.
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Instrumentation and Detectors
A critical consideration of X-ray detectors based on Ga2O3: excitation, carrier transport mechanisms and performance standardization
Alfred Moore, Daniel A Lamb, Lijie Li et al. (+11 more)
X-ray detection underpins a wide range of applications in medicine, security, industrial inspection, scientific research for non-destructive imaging and material analysis. The rapid development of Ga2O3-based X-ray detectors offers a promising pathway toward next-generation detectors with high sensitivity, low noise, and harsh environment applications, benefiting from its intrinsic material properties such as high density, wide band gap energy, and high thermal-chemical stability. However, the underlying device operating mechanisms, including both carrier excitation and transport processes, have not yet been adequately studied, largely due to the misuse of X-ray sources in previous studies. Besides, benchmarking of device characteristics has been problematic due to experimental or data analysis issues, as well as misunderstandings of the applied equations associated with parameter definitions. In this work, we have designed and performed an instructive research work based on epitaxial beta-Ga2O3:Si and its planar Schottky detectors, measured with energy-tuneable monochromatic X-ray beams on a synchrotron beamline, clarifying the device excitation and carrier transport mechanisms with properly benchmarked device performance. In the end, we propose a set of protocols for correctly measuring and analysing the device performance. The proposed protocols are broadly applicable and can be readily extended to other
semiconductor X-ray detectors.
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All authors Alfred Moore, Daniel A Lamb, Lijie Li, Oliver Fox, Kawal Sawhney, Ciaran Llewelyn, Jon E Evans, Saqib Rafique, Tiantian Chai, John Harrington, Zabeada Aslam, Andrew P Brown, Rik Drummond-Brydson, Yaonan Hou
Optics
Nanoparticle Arrays for Efficient Organic Light-Emitting Diode Emission Management
Aron J. J. Dahlberg, Matas Gužauskas, Malek Mahmoudi et al. (+16 more)
OLEDs are increasingly applied in illumination and displays because they offer excellent color quality, are mechanically flexible, and are self-emissive. However, their usage is limited by low external
quantum efficiency (EQE) and efficiency roll-off at high driving voltages. These limitations, together with demands for smaller pixels and device sizes in emerging technologies, motivate innovations that increase efficiency and allow replacing external optical elements with embedded solutions. Here, we demonstrate enhanced outcoupling as well as directional and polarization control of OLED emission, based on collective surface
lattice resonances of plasmonic nanoparticle arrays that are embedded in the active layers of four different state-of-the-art OLED structures. Both square arrays and more complex
lattices producing flat bands are demonstrated to guide the light to directions and polarizations determined by their optical modes. We show that by the design of the array geometry and the OLED structure, spectral and angular enhancement of the electroluminescence (EL), up to 30 %, can be achieved. Our results verify that surface
lattice resonances of nanoparticle arrays offer a robust and versatile embedded solution for tailoring the OLED emission, as well as exciting prospects for efficiency increase if combined with narrow-spectrum emitters.
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All authors Aron J. J. Dahlberg, Matas Gužauskas, Malek Mahmoudi, Joel Lehikoinen, Dmytro Volyniuk, Manish Kumar, Anton Matthijs Berghuis, Hassan A. Qureshi, Rasa Keruckiene, Michael A. Papachatzakis, Evgeny A. Mamonov, Rebecca Heilmann, Henri Lyyra, Olli Siltanen, William L. Barnes, Jaime Gómez Rivas, Konstantinos S. Daskalakis, Juozas Vidas Gražulevičius, Päivi Törmä
Instrumentation and Detectors
Exploiting the latent space of deep AutoEncoders for the identification of signal pulses in noisy time-series
Gioacchino Alex Anastasi, Sebastiano Francesco Albergo, Marzio De Napoli et al. (+3 more)
We propose a data-driven procedure, based on convolutional variational autoencoders, to identify the presence of signal pulses in long time-series. The
dataset consists of synthetic waveforms, each composed of non-gaussian noise and a log-normal shaped signal of variable intensity, with a length of 10,000 samples. The model heavily compresses the input waveforms, allowing a direct study of such a reduced representation. After training for 150 epochs on 7,500 waveforms, a region in the latent space where the network encodes time-series presenting only background noise emerges, allowing in turn to tag as candidates for containing a signal those falling outside. When applied on a test
dataset of freshly generated waveforms, 100% of the events with a large pulses are correctly labelled, and this fraction only decreases for signal amplitudes comparable with accidental noise pulses. This approach was designed to fully exploit the measurements in dual-phase
Liquid Argon Time Projection Chambers, as the one of the
Recoil Directionality experiment, built in the context of the Darkside project.
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All authors Gioacchino Alex Anastasi, Sebastiano Francesco Albergo, Marzio De Napoli, Noemi Pino, Sebastiana Maria Puglia, Alessia Rita Tricomi
Fluid Dynamics
Gradient-free learning of a closed-loop wall controller for turbulent drag reduction
Giorgio Maria Cavallazzi, Miguel Pérez Cuadrado and Alfredo Pinelli
Closed-loop wall controllers learnt by multi-
agent reinforcement learning are usually trained on periodic boxes far smaller than the flows they are meant to drive, and a large part of their drag reduction is lost when they are carried across. Retraining on the target domain is not an affordable remedy: the centralised critic that assigns credit to each wall patch degrades as patches are added, the zero-net-mass constraint couples the patches it is asked to separate, and the episodes must be collected in sequence at a cost that grows with the domain. We propose instead a short gradient-free refinement stage, applied to the transferred policy on the domain it will drive. An
evolution strategy scores whole flow episodes against a regularised objective, so no credit has to be assigned to individual patches, and the candidates in a generation are independent and run in parallel. Applied to a recurrent multi-
agent policy trained on a minimal flow unit at $\Retau\simeq180$ and evaluated on a channel sixteen times larger in wall-parallel area, a few generations raise the drag reduction from $19.0\%$ to $25.7\%$, above the $22.5\%$ of opposition control. Because the policies before and after refinement share an architecture and a training history, the difference between the controlled flows follows from the refinement alone. It shows in the friction decomposition, in the Reynolds stresses and in the near-wall spectra, and the actuation moves from a weak coupling to the wall-normal velocity towards a strong coupling to the streamwise fluctuation.
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Atomic Physics · Cross-listed from gr-qc
High-Frequency Gravitational Wave Constraints from Precision Spectroscopy
Dmitry Budker, Valerie Domcke, Joachim Kopp et al. (+1 more)
Gravitational waves affect the propagation of electromagnetic waves in
laser cavities, modulating the frequency of emitted
photons. We use this effect to search for high-frequency gravitational waves between 100 kHz and 100 MHz using optical precision spectroscopy. Our limits constrain much of this frequency range for the first time. We discuss future improvements of the technique, which we expect to enhance the sensitivity by eight orders of magnitude, and to extend the frequency coverage up to at least 1 GHz.
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All authors Dmitry Budker, Valerie Domcke, Joachim Kopp, Oleg Tretiak
Optics · Cross-listed from quant-ph
Constructing mode-resolved quantum optical models for emitters in photonic crystals
Antonio Morales-Pérez, Iñaki García-Elcano, Chiara Devescovi et al. (+3 more)
Recent advances are enabling
quantum emitters to interact with photonic
crystals, whose electromagnetic modes exhibit complex dispersion relations, spatial mode structure, and polarization textures. However, modeling light-matter behavior in these systems faces a persistent trade-off: electromagnetic approaches based on Maxwell-equation solvers provide realistic vectorial descriptions but are difficult to integrate with
quantum many-body and non-perturbative methods, whereas simplified
quantum-optical
lattice models are tractable but typically rely on scalar and spatially independent light-matter couplings that miss essential features of these structured photonic environments. Here, we introduce a constructive framework to derive
quantum-optical
lattice descriptions that overcome this trade-off. Combining
symmetry-constrained tight-binding constructions with numerically computed photonic band structures and field profiles, our method yields minimal,
symmetry-enforced
lattice Hamiltonians that reproduce the target photonic dispersion while retaining the mode-resolved (position- and polarization-dependent) structure of the light-matter coupling. We show that these models recover Green's-function-based emitter dynamics in the perturbative regime, while providing access to non-perturbative
quantum dynamical simulations beyond emitter-only descriptions. As a proof of principle, we apply the framework to a two-dimensional photonic
crystal and show that it captures polarization-dependent directional emission inaccessible to scalar models, while enabling the analysis of non-Markovian light-matter dynamics and
entanglement. Our results provide a practical bridge between classical electromagnetic simulation tools and
quantum-optical many-body and non-Markovian modeling in photonic
crystal settings.
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All authors Antonio Morales-Pérez, Iñaki García-Elcano, Chiara Devescovi, Maia G. Vergniory, Aitzol García-Etxarri, Alejandro González-Tudela
Space Physics
Unraveling the Generation Mechanism of a Mid-Latitude Plasma Blob and the Evidence of Its Rare Interaction with a MSTID Phase Front
D. Patgiri, R. Rathi, V. Yadav et al. (+10 more)
We report observations of two distinct nighttime F-region irregularities,
plasma blob (localized density enhancement) and medium-scale traveling ionospheric disturbance (MSTID), in O(1D) 630.0 nm all-sky airglow images from Hanle (32.7{\deg}N, 78.9{\deg}E; Mlat~24.1{\deg}N), Ladakh, India, during the geomagnetically quiet (Ap=6) night of 06 July 2021. Global vertical total electron content (VTEC) maps revealed that the
plasma blob developed beyond the southern edge of imager's field-of-view before appearing in airglow images and propagated predominantly westward, as confirmed from both the airglow and VTEC
datasets. The existence of the
plasma blob and MSTID outside the imager field-of-view was further confirmed by temporal VTEC fluctuations recorded by multiple GNSS receivers. Additionally, FORMOSAT-7/
COSMIC-2 signal-to-noise ratio and ICON/MIGHTI wind profiles indicated the presence of sporadic-E (ES) layers at E-region near both the
plasma blob and the MSTID. We propose that polarization electric field associated with either MSTID or ES-layers mapped along
magnetic field lines to lower latitudes, driving upward
plasma transport from F-peak region through vertical uplift of the F-layer. This F-layer uplift was confirmed by simultaneous in-situ O+/H+ density enhancements/reductions at LEO altitudes measured by FORMOSAT-7/
COSMIC-2. Upward-transported
plasma experienced reduced chemical loss at higher altitudes, producing localized VTEC enhancements (
plasma blob). The
plasma subsequently diffused along
magnetic field lines to higher/lower latitudes/altitudes (~250 km), entering imager's field-of-view, where enhanced dissociative recombination of O2+ produced high intensity airglow region. Interestingly, interaction between the
plasma blob and MSTID's
plasma-depleted front caused gradual decay and bifurcation of the front due to
plasma influx from the high-density blob region.
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All authors D. Patgiri, R. Rathi, V. Yadav, D. Chakrabarty, M. V. Sunil Krishna, S. Kannaujiya, S. Sunda, Y. Otsuka, A. Shinbori, M. Nishioka, S. Perwitasari, P. Pavan Chaitanya, S. Sarkhel
Fluid Dynamics
Aerosol generation by the splashing of low viscosity drops impacting liquid layers
Guillaume Riboux and José Manuel Gordillo
Using theory and numerical simulations, here we describe the early stages of the impact with a velocity $V$ of a drop of radius $R_d$ of a low viscosity
liquid such as water against a layer of generic thickness $H$ of the same
liquid. Our predictions for the initial velocity $V_t\gg V$ and the diameter $H_t\ll R_d$ of the toroidal rim bordering the edge of the thin lamella which is ejected radially outwards after the impact, are in fair agreement with both the numerical results and also with the experimental measurements reported by Zhang et al [J. Fluid Mech, 690, 5, 2012]. Consequently, the present findings can be employed, for instance, to predict the initial diameters and velocities of the fastest tiny droplets which are ejected right after a rain drop falls on a
liquid pool, an ubiquitous phenomenon with implications in the dispersal of contaminants and in the generation of aerosols and of ice condensation
nuclei
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Atomic Physics
Optically Derived Radio-Frequency Benchmark in Methanol: A Sub-kHz Reference for Astrophysical Tests of Fundamental Physics
Frank M. J. Cozijn, Arthémise Altman, Alexandr S. Bogomolov et al. (+8 more)
Methanol
radio lines observed in space provide sensitive probes of whether the
proton-to-electron mass ratio has changed over
cosmic time, but such tests require laboratory rest frequencies with very high accuracy. Here we determine the frequency of the astrophysically important 12.2 GHz $3_{-1}$E – $2_{0}$E transition of CH$_3$OH by measuring near-infrared rovibrational transitions rather than the microwave line directly. Using wavelength-modulated NICE-OHMS locked to an ultra-stable optical frequency comb and referenced via a fiber link to a hydrogen-maser frequency standard, we measure Lamb-dip frequencies near 1.4 $\mu$m (216 THz) with 10 Hz statistical reproducibility and absolute uncertainties as low as 130 Hz. Pairs of optical transitions sharing common upper levels form a triangulation scheme that yields the ground-state rotational combination difference. We obtain 12 178 596.415(135) kHz, improving on earlier molecular-beam microwave spectroscopy by a factor of 20 and agreeing with a recent free-induction-decay measurement. This result establishes a sub-kHz laboratory
benchmark for a key
radio-astronomical methanol line and demonstrates that optical triangulation can be extended to non-
chiral molecules with internal rotation.
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All authors Frank M. J. Cozijn, Arthémise Altman, Alexandr S. Bogomolov, Alexis Libert, Simon Collignon, Erik Dierikx, Jeroen C. J. Koelemeij, Boy Lankhaar, Isabelle Kleiner, Clément Lauzin, Wim Ubachs
Atomic Physics
Coherence enhancement of Rydberg polaritons
Xiao-Feng Shi, Yan Lu, Yuechun Jiao et al. (+1 more)
Quantum nonlinear optics by Rydberg polaritons can enable single-
photon transistor and switch, single-
photon source, and deterministic
quantum information processing. A major hindrance in this study is the fast motional decoherence. Here, we devise a scheme to significantly enhance the coherence of Rydberg polariton by letting the atoms remember their velocities, or, alternatively, by changing the phase of Rydberg polariton according to its storage time. After the Rydberg polariton is prepared with a Rydberg state $|r_1\rangle$, i.e., during the storage time, two
laser fields induce a transition between $|r_1\rangle$ and a nearby Rydberg state $|r_2\rangle$ via a low-lying intermediate state $\lvert f\rangle$ which is largely detuned. In particular, we find that either a $2\pi\mathbb{N}$ protocol, a $\pi$-wait-$\pi$ protocol, or a wait-$\pi$ protocol, along with an appropriate choice of $\lvert f\rangle$ can lead to a phase-coherent Rydberg polariton upon its
retrieval. Importantly, the coherent transition between $|r_1\rangle$ and $|r_2\rangle$ ensures that the Rydberg polariton can block the Rydberg excitation of nearby atoms as in usual applications of Rydberg polaritons. Numerics show that the theory can nearly completely eliminate the motional dephasing, leaving Rydberg-state decay as the only fundamental channel of decoherence. This sheds light on a broad application of Rydberg-mediated
quantum nonlinear optics.
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All authors Xiao-Feng Shi, Yan Lu, Yuechun Jiao, Jianming Zhao
Plasma Physics
First reduced model for integrated computations of helicon wave heating and current drive in magnetic fusion plasmas
Zi-Chen Kan, Lei Chang, Zhen-Yu Wang et al. (+9 more)
Fast predictive modelling of
radio-frequency heating and current drive is important for integrated tokamak scenario design, yet kinetic calculations of helicon-wave absorption remain too computationally expensive for large-scale parameter scans. We present a reduced model for helicon-wave heating and current drive that retains the dominant parallel electron Landau-damping channel. The wave response is evaluated on the cold-
plasma dispersion root, and a single-Landau-pole correction is introduced to obtain compact expressions for the local damping rate and current-drive efficiency. The model is benchmarked against the Chiu-Chan heating model using approximately 1.6 million samples covering representative conditions of EAST, HL-3, DIII-D and KSTAR. The reduction error is found to be governed primarily by the electron Landau parameter and electron beta. Within an identified sub-lower-hybrid-frequency validity window, results from different devices collapse onto a common error curve, which enables an empirical correction that is further tested using ITER-like and BEST-like extrapolation cases. Near and above the lower-hybrid frequency, the agreement deteriorates rapidly owing to changes in the cold-dispersion root structure and the breakdown of the single-branch WKB description. When coupled to a reduced current-drive source, the corrected heating model gives a median deviation of 10.8 percent from the Landau-channel Ehst-Karney reference and reproduces published CFETR current-density profiles. The resulting model provides a computationally efficient reduced closure for helicon-wave heating and current-drive calculations, together with physically interpretable limits on its range of validity.
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All authors Zi-Chen Kan, Lei Chang, Zhen-Yu Wang, Hua-Sheng Xie, Ping-Wei Zheng, Lai Wei, Qi-Bin Luan, Xue-Mei Zhai, Zhao-Qing Hu, Zheng-Xiong Wang, Matthew Hole, Zhi-Song Qu
Data Analysis and Statistics · Cross-listed from stat.ME
Symbolic Weak-form Recovery of 2-D Stochastic Generators
Sai Sathvik Gullipalli and Eshwar R A
Recovering two-dimensional Ito generators from trajectory data is difficult because drift increments have low signal-to-noise, bivariate weak designs can be ill-conditioned, and unconstrained tensor estimates need not be positive semidefinite. We study WG-SINDy
estimator combining covariance-shaped spatial kernels, a ridge-stabilized local-
polynomial projection, adaptive-LASSO/STLSQ selection, one in-sample per-component feasible diagonal GLS pass, and a PSD projection–Cholesky read-out with mild isotropic shrinkage. The released
estimator uses a data-dependent full-cloud smoother and one in-sample per-component feasible diagonal GLS pass; accordingly, we do not claim exact finite-sample martingale cancellation or a feasible-GLS efficiency
theorem for the reported implementation. We evaluate the
estimator on 29 synthetic two-dimensional systems: 19 meet their declared per-system recovery contracts, eight are retained as named limits, and two remain scoped reviews. Across the 19 PASS rows, the median central-grid drift metric is 0.204 and the median tensor error is 0.0397. Among the six systems with a finite, non-degenerate off-diagonal target, the median $a_{12}$ cosine is 0.997. Positive-semidefinite validity is imposed by construction. These results are synthetic, in-sample sampled-region diagnostics and do not establish universal or real-data recovery.
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Geophysics · Cross-listed from astro-ph.EP
Discrimination of Tectonic, Swarm and Impact-related Marsquakes using Spectral Characteristics
Simon C. Stähler, Savas Ceylan, Nikolaj Dahmen et al. (+2 more)
The NASA InSight mission observed over 2000 marsquakes in the course of its three year mission. These quakes varied in magnitude between 1.5 and 4.5, as well as in spectral content. We present a simple framework to describe the spectral characteristics of all observed marsquakes, based on source process; propagation through the mantle or crust; and local, receiver-side amplification. We assign to each quake an objective measure of its amplitude, as well as the spectral decay created by the duration of the rupture and the dampening of high frequencies due to visco-elastic attenuation. Together, this allows us to obtain characteristic patterns of the whole marsquake
dataset, e.g. in terms of event magnitudes, source size, and - for quakes caused by meteoritic impacts - crater size. We show that a significant fraction of all marsquakes - the high-frequency quakes - form a swarm that is likely not caused by tectonic processes in rocks. Our analysis allows separation of the whole marsquake catalogue into three event classes, of tectonic quakes, meteoritic impacts, and swarm events. We finally conclude that the largest marsquake, S1222a, most likely belongs to the group of meteoritic impacts.
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All authors Simon C. Stähler, Savas Ceylan, Nikolaj Dahmen, John Clinton, Domenico Giardini
Fluid Dynamics
Variable-Lattice-Density Optimization of Pin-Fin Heat Sinks under High-Reynolds-Number Flow Conditions
Yoshikatsu Furusawa, Kunitaka Shintani, Shunsuke Hirotani et al. (+1 more)
This study extends variable-
lattice-density optimization to high-Reynolds-number flows for the design of periodically arranged pin-fin heat sinks. Effective permeability and drag coefficient are identified from unit-
cell Reynolds-averaged Navier–Stokes analyses of cylindrical pin-fin arrays and incorporated into a reduced model based on the Darcy–Forchheimer law for macroscopic design exploration. To enable stable optimization under high-Reynolds-number conditions, a dual-mesh framework is introduced, in which the flow field and sensitivities are evaluated on a fine mesh, whereas the design variables are updated on a coarse mesh corresponding to the unit-
cell arrangement. For the base condition, the $L_2$ norm of the temperature deviation from the area-averaged temperature is decreased from 4.38 K to 1.00 K in the reduced model, and geometry-resolved analysis of the reconstructed design confirms a reduction from 5.98 K to 1.17 K. Additional calculations with higher inlet velocities and modified outlet locations show that the proposed method captures the dominant flow-redistribution trends under different operating and
geometric conditions, although the thermal objective became less accurate when local solid-temperature variations became pronounced. These results indicate that the proposed approach is useful as practical design-exploration for identifying candidate pin-fin heat sink configurations under high-Reynolds-number conditions.
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All authors Yoshikatsu Furusawa, Kunitaka Shintani, Shunsuke Hirotani, Kentaro Yaji
Data Analysis and Statistics · Cross-listed from math.PR
Renormalisation of Inhomogeneous Random Graphs
Luca Avena, Diego Garlaschelli, Rajat Subhra Hazra et al. (+1 more)
We consider inhomogeneous random graphs in which vertices are assigned i.i.d.\ random weights, pairs of distinct vertices are connected by an edge independently with a probability that is a bi-variate function of the weights of the vertices, and single vertices are connected to themselves by a self-loop independently with a probability that is a uni-variate function of the weight of the vertex. We apply a renormalisation transformation in which vertices are aggregated into groups of equal size according to a greedy
algorithm, namely, distinct groups of aggregated vertices are connected by an aggregated edge if and only if there is at least one edge connecting two constituent vertices across the groups, while a group of aggregated vertices is connected to itself by an aggregated self-loop if and only if there is at least one self-loop at an internal vertex or one edge connecting a pair of distinct internal vertices. We analyse what happens when the renormalisation transformation is iterated. In particular, we show that, starting from appropriately scaled connection functions, the iterated renormalised graphs converge to a two-parameter family of random graphs, acting as an attractor in a universality class. We consider a light-tailed regime, for which the scaling limit is a homogeneous Erdős–Rényi random graph, and a heavy-tailed regime, for which the scaling limit is an inhomogeneous random graph with stable infinite-mean random weights and an exponential disconnection function. Different scalings are needed for the two regimes. Which of the two regimes prevails depends on the choice of the connection functions and the choice of the law of the random weights.
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All authors Luca Avena, Diego Garlaschelli, Rajat Subhra Hazra, Frank den Hollander
Plasma Physics
Impact of Residual Angular Chirp in a Petawatt-class Laser System on Laser-driven Proton Acceleration
Qingfan Wu, Minjian Wu, Jiarui Zhao et al. (+25 more)
Laser-driven
proton acceleration has attracted considerable interest owing to its appealing potential in versatile applications including cancer therapy.
Proton energies depend critically on the on-target intensities, yet the detrimental impact of focal spot degradation induced by spatiotemporal couplings on the acceleration remains insufficiently elucidated. In this study, we demonstrate that residual angular chirp (AC), stemming from minor misalignments of the grating compressor in a Petawatt-class
laser system, acts as a critical bottleneck for
proton acceleration. Experimental results reveal that even around 100 microradians of grating misalignment induces substantial focal-spot elongation and a pronounced reduction in peak intensity. By implementing an in situ spectral-blocking diagnostic, we effectively eliminated the residual AC and restored a near-diffraction-limited focus. This optimization led to a significant recovery of the on-target intensity, resulting in a twofold increase in the
proton cutoff energy. Our work presents a successful demonstration of diagnosing and eliminating residual AC. This provides a practical reference for generating high-energy
proton beams and supporting their diverse applications in a PW-class
laser.
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All authors Qingfan Wu, Minjian Wu, Jiarui Zhao, Ying Gao, Haoran Chen, Tan Song, Zhongshuai Zhang, Zhangyi Wu, Tianhao Liang, Shirui Xu, Ziyang Peng, Hui Zhang, Tianqi Xu, Qihang Han, Chenghao Hua, Ke Chen, Pengcheng Fan, Yuntian Xie, Xianduo Li, Peiqiang Liu, Xiangyu Nong, Shengxuan Xu, Liyong Ma, Yixing Geng, Chen Lin, Yanying Zhao, Xueqing Yan, Wenjun Ma
Plasma Physics
Radiation reaction measurements via single-shot energy-loss determination in high-intensity laser-electron collisions
Philipp Sikorski and Daniel Seipt
Effects of radiation reaction are considered a key factor for
lasers-
plasma-interactions at ultra-high intensities, and gaining precise understanding of these phenomena will be crucical for discoveries of novel strong-field QED effects. In this paper we investigate an experimental geometry that allows a direct single-shot measurement of radiation reaction energy losses in high-intensity
laser-beam collisions. This is made possible by simultaneous measurements of the pre-collision and post-collision electron beam spectra in a single shot by employing a dedicated 90-degree scattering geometry between the electron beam and the colliding high-power
laser. We discuss the principal requirements and design constraints, e.g. for the electron beam divergence and source size. We derive an analytic expression for the correlation between the final particle energy and the scattering angle. Numerical simulations are performed employing both classical and
stochastic quantum radiation reaction models to predict the experimental outcome and demonstrate the feasibility of the scenario.
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Fluid Dynamics
Emergent coordination and propulsion of a model spherical ciliate
Hang Su, Timothy A Westwood and Eric E Keaveny
A longstanding challenge in biofluid dynamics research is a mechanistic understanding of the coordinated movement of motile cilia and its resulting ability to facilitate fluid transport. In this study, we develop numerical techniques to simultaneously compute the emergent coordination of and propulsion by filamentous model cilia covering the surface of a sphere. To accomplish this, we develop what we refer to as the filament oscillator model, in which each cilium has two dynamic degrees of freedom: a phase variable that maps to a specific shape in a prescribed sequence, and an angle that describes the overall orientation of the sequence. By varying a parameter related to cilium stiffness, we show that there is bistability between
symplectic-like and diaplectic metachronal waves, provided that the stiffness is sufficiently low. Above the critical stiffness, only diaplectic waves emerge. Further, we analyse the propulsive capabilities and flow fields of the two emergent states, showing that diaplectic waves provide more efficient propulsion due to their shorter wavelengths. In addition, we examine how introducing beat-plane tilt leads to ciliate rotation while maintaining nearly identical emergent states and comparable swimming speeds.
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