Optics
A high-Q Split Cavity Enabling Independent Electrical Tuning of two Quantum Dots
Lan Hoang Mai, Nazifa Tasnim Arony, R S Joshya et al. (+3 more)
Cavity-mediated strong coupling is an essential tool for
quantum photonics. However, the inherent inhomogeneity in ensembles of matter-based
qubits necessitates independent tuning to bring more than one
qubit into resonance with a single cavity mode. We present the design, fabrication, and characterization of a GaAs-based photonic
crystal split cavity that consists of two electrically-distinct portions, which preserves the ability to apply independent electric fields that would independently tune two distinct
qubits based on InAs
Quantum Dots (QDs) into resonance with a cavity mode. We show that this device, despite the cut required to electrically isolate the two halves, achieves an average Q $\geq 20,000$, sufficient to enter the strong coupling regime. Moreover, we show that the Q is limited primarily by the precision and accuracy of the e-beam lithography tool, rather than by sidewall scattering. This result creates a realistic experimental path toward devices that use controlled interactions between two InAs QDs, mediated by strong coupling to a single cavity mode, to generate multi-dimensional
photon graph states.
Read the full abstract ▾
All authors Lan Hoang Mai, Nazifa Tasnim Arony, R S Joshya, Tyler Manfre, Joshua M. O. Zide, Matthew F. Doty
Geophysics · Cross-listed from cs.SD
An End-to-End Workflow for Fin Whale Song Detection, Note Characterization, and Localization with Distributed Acoustic Sensing
Dídac Diego-Tortosa, Miriam Romagosa, Arantza Ugalde et al. (+4 more)
Submarine fiber-optic cables instrumented with distributed acoustic sensing (DAS) provide an effective approach for large-scale monitoring of fin whales. We present an end-to-end workflow for detecting, characterizing, and localizing fin whale notes, tested on two submarine telecom cables in the Strait of Gibraltar and western Alboran Sea. The workflow applies a kurtosis-value picker adapted to narrow-band fin whale notes. Channel-wise detections are grouped into individual notes using density-based spatio-temporal clustering, cluster agglomeration, and
hyperbolic fitting to reject incoherent picks. The retained clusters are characterized through temporal, spectral, and energy-related descriptors that support note-type discrimination and estimation of inter-note intervals. Relative arrival times across DAS channels are then used in a grid-search procedure to estimate candidate source locations. Evaluation against manually annotated detections from six fin whale songs yielded median pick-level precision of 0.990 and recall of 0.744, and median cluster-level precision of 0.880 and recall of 0.806. Representative applications demonstrate separation of overlapping vocalizations, characterization of type-A and type-B notes, and the inference of apparent source movement. By transforming dense DAS recordings into compact note-level bioacoustic information, the workflow provides an integrated framework for fin whale monitoring and a basis for adaptation to other synchronized acoustic receiver arrays.
Read the full abstract ▾
All authors Dídac Diego-Tortosa, Miriam Romagosa, Arantza Ugalde, Hugo Latorre, Sergi Ventosa, Jose Enrique García, Antonio Villaseñor
Mesoscale and Nanoscale Physics
Second-harmonic generation in twisted double bilayer graphene: Double-resonant enhancement from moiré flat bands
Takaaki V. Joya, Takuto Kawakami and Mikito Koshino
We theoretically investigate second-harmonic generation (SHG) in twisted double
bilayer graphene (TDBG) with AB–AB and AB–BA stacking configurations using a perturbative approach based on an effective continuum
Hamiltonian. We present a systematic analysis of the SHG response as a function of twist angle, vertical bias voltage,
Fermi energy, and stacking configuration. We find that the SHG signal is strongly enhanced at small twist angles due to the emergence of moiré flat bands and the associated increase in the joint density of states. Beyond this conventional enhancement mechanism, we demonstrate that the reduced bandwidth enables a pronounced double-resonant process, in which optical transitions at both $\omega$ and $2\omega$ are simultaneously satisfied over extended regions of the moiré Brillouin zone. This mechanism leads to a substantial amplification of the SHG response, analogous to the enhancement observed in systems with discrete energy levels, but realised here in a tuneable moiré band structure. Furthermore, we show that the AB–AB and AB–BA configurations exhibit a systematic $\pi$ phase shift in the SHG response at large bias voltages, reflecting their distinct
symmetry and electronic structure. Our results identify double-resonance effects as a generic mechanism for enhancing SHG in moiré systems and provide a unified framework for understanding and controlling nonlinear optical responses in tuneable flat-band materials.
Read the full abstract ▾
Nuclear Theory
Effects of light-cluster degrees of freedom on collective flows in heavy-ion collisions at FOPI energies
Xin Li, Si-Pei Wang, Rui Wang et al. (+4 more)
Within a
lattice Boltzmann-Uehling-Uhlenbeck transport model coupled to a kinetic approach for light-cluster formation, we investigate the impact of explicit light-cluster degrees of freedom on collective flows in Au+Au collisions at FOPI energies with beam energies $E_{\rm beam}$= $120$–$1500 A$ MeV by using a density-, momentum-, and isospin-dependent N$5$LO Skyrme pseudopotential. We first
benchmark the kinetic approach by comparing the calculated light-cluster yields with FOPI data in central Au+Au collisions. We then analyze the collective flows of
protons and light
nuclei (deuterons, tritons, $^{3}\mathrm{He}$, and $^{4}\mathrm{He}$) in mid-central collisions. For
protons, calculations with and without dynamical light-cluster degrees of freedom are compared to quantify the influence of dynamical cluster formation on
proton directed ($v_1$),
elliptic ($v_2$), triangular ($v_3$), and quadrangular ($v_4$) flows. We find that the dynamical light-cluster effect appreciably modifies
proton $v_1$–$v_4$ flows at $E_{\rm beam}=120$–$150 A$ MeV, remains visible at $E_{\rm beam}=250$–$400 A$ MeV, and gradually weakens at $E_{\rm beam}\gtrsim 600 A$ MeV. For light
nuclei, the kinetic approach captures the overall beam-energy dependence of the FOPI flow data, with better agreement for $E_{\rm beam}\geq 400 A$ MeV. We further examine the nucleon-number scaling of $v_2/A$ in both model calculations and experimental data, finding that the kinetic light-cluster formation approach qualitatively reproduces the observed scaling behavior. These results highlight the importance of a dynamical treatment of light-cluster formation for interpreting collective flows in heavy-ion collisions below about $600 A$ MeV, although the clustering effects on
proton flows are minor at higher collision energies.
Read the full abstract ▾
All authors Xin Li, Si-Pei Wang, Rui Wang, Zhen Zhang, Jie Pu, Chun-Wang Ma, Lie-Wen Chen
Solar and Stellar Astrophysics
Statistical insights on the decorrelation lengths of solar wind parameters at L1 point under varying conditions
Yogesh, Aparupa Apsara Baruah, Dibyendu Chakrabarty et al. (+3 more)
Understanding the spatial coherence of
solar wind
plasma and
magnetic field properties is essential for interpreting multi-spacecraft observations and for characterizing the large-scale structure of heliospheric transients. In this study, we quantify the spatial correlation of six key
solar wind parameters - interplanetary
magnetic field components, bulk flow speed,
proton number density, and the alpha-to-
proton abundance ratio - using simultaneous measurements from the ACE and Wind spacecraft as a function of their instantaneous separation distance. The analysis is performed separately for intervals of background
solar wind, Interplanetary Coronal Mass Ejections (ICMEs), and Stream Interaction Regions (SIRs). The decay of the Pearson correlation coefficient with distance is modeled using an exponential function to infer characteristic de-correlation length scales. We find that the bulk
solar wind speed is the most spatially coherent parameter in all regimes, while
plasma composition exhibits the weakest coherence.
Magnetic field coherence shows strong dependence on
solar wind structure: ICMEs display near-unity correlations and the largest
magnetic coherence scales, consistent with organized, flux-rope-like configurations, whereas SIRs exhibit reduced coherence - particularly in the north - south
magnetic field component - reflecting compressed and turbulent
plasma. The background
solar wind exhibits intermediate behavior, with large-scale coherence in bulk
plasma properties but shorter coherence lengths in
magnetic fluctuations. These results provide a quantitative framework for distinguishing
solar wind structures based on their spatial coherence properties and have important implications for multi-point
solar wind studies and space weather applications.
Read the full abstract ▾
All authors Yogesh, Aparupa Apsara Baruah, Dibyendu Chakrabarty, Kalyan Bhuyan, Aakash Gupta, Gregory G. Howes
Disordered Systems and Neural Networks
Bayesian Inference with Structured Signal: Static Replica Symmetry Breaking on the Nishimori Line in the Planted Spin Glass
Andrea Vincenzo Dell'Abate and Louise Budzynski
A common assumption in theoretical models of
Bayesian inference is that the signal has i.i.d. components. To study the effect of correlations in the signal prior, we consider a minimal model: the planted
spin glass on random regular graphs, where the signal is sampled from an Ising model with coupling $\kappa$. Depending on the phase of the prior, we find that adding structure in the signal can either help or hinder inference. In the paramagnetic regime, correlations in the signal lower the reconstruction threshold, so that weaker signal strength is sufficient for recovery. In the
ferromagnetic regime, the prior alone already enables partial recovery, and we identify the threshold above which the observations provide additional information. When the prior itself is in a replica
symmetry breaking (RSB) phase, we detect a static RSB transition in the posterior under Nishimori conditions. This provides an example where a non-separable, correlated prior leads to static RSB in a Bayes-optimal inference problem. We discuss the consequences of this glassy phase for algorithmic performance, in particular for Belief Propagation.
Read the full abstract ▾
Cosmology and Nongalactic Astrophysics
Axial Bianchi IX meets Gaia data
Thomas Schücker
The aim of the present work is two-fold: {\it(i)} Compute the drift of comoving extragalactic sources in axial Bianchi IX universes, in particular in those satisfying Einstein's equations with positive cosmological constant and comoving
dust. {\it(ii)} Linearize this drift (and for comparison the previously calculated Lemaître-Hubble diagram) simultaneously in small anisotropy and in small positive
curvature. We find that the drift in this linear approximation coincides with the drift in axial Bianchi I universes. This is not true for Lemaître-Hubble diagrams.
Read the full abstract ▾
High Energy Physics (Theory)
Subleading Asymptotic Charges in Massless Scalar QED
Éanna É. Flanagan and Zhihan Liu
We study subleading asymptotic charges of a U(1) gauge field coupled to a charged massless scalar field in Minkowski spacetime. We consider a phase space for which the scalar-field initial data on null infinity have compact support, while the gauge-field initial data admit an asymptotic expansion with inverse-power tails in retarded (advanced) time, which we refer to as initial-data tails. We identify three finite charges at the null infinities which are conserved under scattering. One is a renormalized version of the standard subleading soft charge. The second is a logarithmic charge which is the difference of the coefficients of the leading order tails at the future and past ends of null infinity. The third is a new charge that probes the average of the tail coefficients. We
conjecture that the third charge is associated with a new class of large gauge transformations which diverge linearly in retarded time.
Read the full abstract ▾
Geophysics
Network-Based Subbasin-Scale Mapping of Streamflow Alteration in Ontario, Canada
Hongren Shen, Bryan A. Tolson, James R. Craig et al. (+3 more)
Dams, reservoirs, and waterpower facilities support regional water management but can alter streamflow far downstream through connected river networks, complicating hydrologic modeling and aquatic ecosystem assessment. Existing indicators typically quantify alteration only at discrete locations, limiting spatially continuous mapping of potential infrastructure influence. We propose the Streamflow Alteration Index (SAI), a network-based screening metric that propagates point-based alteration signals downstream through a routing network. The framework includes paired indices, SAI_I and SAI_II (0-100%), representing influence from confirmed (Level I) and potential (Level II) alteration sources. We implemented SAI for Ontario, Canada, using the Ontario Lake and River Routing Product Version 2 (OLRRP v2) and an inventory of 643 alteration signal sources compiled from provincial
datasets. The resulting SAI v1.0 database provides seamless, high-resolution, subbasin-scale mapping and estimates at gauged and ungauged network nodes. We validated SAI by classifying gauged subbasins as natural, conditional, or altered and comparing these classes with two independent references: Reference Hydrometric Basin Network gauges and Water Survey of Canada (WSC) Natural and Regulated labels. SAI classified 86% of RHBN natural gauges and 86% of WSC-natural gauges as natural. Among WSC-regulated gauges, 74% were classified as conditional or natural. SAI v1.0 therefore provides an objective screening product for large-domain hydrologic and aquatic applications without requiring detailed dam operating information and offers a scalable basis for national- to global-scale mapping of potential streamflow alteration.
Read the full abstract ▾
All authors Hongren Shen, Bryan A. Tolson, James R. Craig, Robert A. Metcalfe, Jonathan Romero-Cuellar, James J. Luce
Superconductivity
Superconducting ternary compounds Li-X-B (X=Mo, W) within the mild pressure range: First-principles predictions
Bangshuai Zhu, Juefei Wu, Dexi Shao et al. (+6 more)
Among the superconducting hydrides under high pressure, a number of studies concentrate on the ternary compounds to explore unique
superconductors, which are capable of reducing the stable pressure and maintain superconductivity. In this work, to verify our proposed strategy of ternary composition lines (TCLs) to explore ternary compounds, we combined the first-principles calculations and
crystal structure predictions to study the ternary compounds Li-X-B (X=Mo, W) under high pressure. After calculations along five and four TCLs in Li-W-B and Li-Mo-B, respectively, five Li-W-B compounds and four Li-Mo-B compounds were predicted. The compositions of LiWB4, Li4MoB2 and LiMo2B2 could be thermodynamically stable under high pressure, and Li2WB6 is around 0.02 eV/atom above the convex hull at 0 GPa, which has potential for synthesizing. Both of the predicted Li2WB6 P6/mmm and Li2WB4 R-3m are superconducting and their Tc are around 11 K, which are similar to the Tc of WB2 P6/mmm around 100 GPa. An anomalous increase of Tc was found in Li4MoB2 C2/m upon compression. We carried out full ternary search (FTS) to evaluate the validity of the TCLs strategy in Li-W-B system at 0 GPa. Our results are helpful for understanding the phase diagram of Li-X-B (X=Mo, W) under high pressure and the introducing of Li atoms provide candidate structures to reduce the measured stable pressure from ~100 GPa in WB2 P6/mmm to 0 GPa. Meanwhile, we preliminary validate the strategy of TCLs in structure predictions and we expect to improve this strategy in the future, shedding light on the studies of ternary compounds.
Read the full abstract ▾
All authors Bangshuai Zhu, Juefei Wu, Dexi Shao, Junjie Wang, Yu Han, Cuiying Pei, Qi Wang, Jian Sun, Yanpeng Qi
Fluid Dynamics
Aerodynamic Drag and Heat Transfer Corrections for Dehydrated Pollen Particles: CFD-Based Modeling of Airborne Allergen Transport in Smart Urban Environments
Omar Hamad, Samer Ali, Mahmoud Khaled et al. (+1 more)
Airborne pollen transport is a key concern for urban air-quality assessment, allergy-risk
forecasting, and smart-city planning. However, conventional dispersion models generally assume smooth spherical particles, neglecting how pollen dehydration alters particle morphology and impacts aerodynamic and thermal behavior. To address this gap, this study presents, for the first time, advanced CFD simulations evaluating the aerodynamic drag forces and convective heat transfer of realistically dehydrated (dry) pollen particles. Investigations are conducted at Reynolds numbers ($0.1 \leq Re_p \leq 15$) at the particle's scale corresponding to realistic atmospheric wind speeds ranging from 0.27 to 30 km/h. The findings reveal that dry pollen particles exhibit drag coefficients 8% to 15% higher than those predicted for hydrated pollen spherical particles. Conversely, their Nusselt numbers are 5% to 15% lower than those for hydrated pollen particles. These considerable deviations confirm that conventional spherical correlations are inadequate for simulating dry pollen Lagrangian transport and evaporation. These findings highlight the need to account for realistic dehydrated shapes when modeling airborne allergen transport in urban environments.
Read the full abstract ▾
All authors Omar Hamad, Samer Ali, Mahmoud Khaled, Talib Dbouk
Optics
Metaphotonic Catalysis: Amorphous silicon metasurfaces encode photochemical activity
Elif Nur Dayi, Priscila Vensaus, Milad Sabzehparvar et al. (+3 more)
Solar-to-fuel conversion can benefit from photoelectrodes with engineered light-matter interactions, yet most nanostructured designs provide limited control over the spatial and spectral distribution of photochemical activity. Here, we present an all-dielectric amorphous-silicon metasurface photoelectrode that confines resonant light-matter interactions within a 220-nm-thick active layer. Tunable Mie-type and guided-mode resonances spectrally encode chemical reactivity and produce absorptance above 80% near the silicon band edge, compared with less than 30% for an unpatterned film of the same thickness. The metasurface simultaneously functions as the light absorber, carrier-transport layer, and catalytic interface without an added co-catalyst or engineered passivation layer. Operando photo-scanning electrochemical microscopy reveals wavelength- and structure-dependent redox activity and a tenfold enhancement in internal
quantum efficiency near the silicon band edge relative to planar films. Power-dependent measurements support a
photon-driven rather than nonlinear photothermal origin of the enhancement, while surface-sensitive ultrafast transient-reflectivity measurements probe the underlying carrier dynamics. Light-coupled scanning electrochemical
cell microscopy further shows hydrogen-
evolution enhancements of up to 21-fold under photocatalytic conditions and 15-fold under photoelectrochemical bias, corresponding to 11.2-fold and 7.7-fold enhancements after accounting for the estimated surface-area increase. The metasurfaces remain stable during more than 10 hours of immersion and prolonged
laser illumination. These results establish amorphous silicon as a stable and versatile platform for resonantly programmed photocatalysis and
solar-fuel generation.
Read the full abstract ▾
All authors Elif Nur Dayi, Priscila Vensaus, Milad Sabzehparvar, Michele Puppin, Omer Can Karaman, Giulia Tagliabue
Quantum Physics
Revealing and reducing growth-induced interfacial disorder in preferentially aligned nitrogen-vacancy centers in diamond
Cheng-I Ho, Marina Davydova, Patrik Straňák et al. (+4 more)
Nitrogen-vacancy (NV) centers in chemical-vapor-deposition (CVD) diamond can form preferentially oriented ensembles with high sensing performance and low densities of
lattice defects. Thin films of this material are a cornerstone of various imaging modalities. However, nitrogen injection needed to produce such films can transiently drive growth out of
equilibrium, generating interfacial strain and
spin defects that degrade NV coherence. Here, we investigate this disorder in $^{12}\text{C}$-enriched, preferentially oriented NV layers grown on (111) diamond using two nitrogen-injection procedures, combined with nanometer-scale selective
plasma etching and NV
spin-coherence measurements. Pulsed nitrogen injection produces a pronounced nitrogen overshoot within a 60–80 nm interfacial region, generating excessive amounts of defects. By contrast, smooth nitrogen delivery through mass flow controllers substantially suppresses interfacial disorder, yielding coherence properties close to the theoretical limit imposed by
spin-bath noise. A 50-nm NV layer is used to demonstrate
proton nuclear magnetic resonance detection. This work reveals the role of interfacial disorder associated with the nitrogen-doping procedure and provides a route to growing high-quality, thin NV-doped layers for
quantum-sensing applications.
Read the full abstract ▾
All authors Cheng-I Ho, Marina Davydova, Patrik Straňák, Felix Hoffmann, Peter Knittel, Andrej Denisenko, Jörg Wrachtrup
Superconductivity
Cryogenic focused-ion-beam microstructuring enabling quantitative $c$-axis transport measurements in Tl$_2$Ba$_2$CuO$_{6+\delta}$
Ayanesh Maiti, Carsten Putzke, Linus Holeschovsky et al. (+10 more)
Absolute transport measurements in correlated
quantum materials are often limited by disorder, inhomogeneity,
geometric uncertainty, and small
crystal size. Focused ion beam (FIB) technology offers a route to overcome many of these limitations by enabling transport devices with precisely defined geometry to be fabricated from lamellae extracted from carefully selected regions of a
crystal, but its application to cuprate
superconductors has been hindered by ion-beam-induced damage. Here we study the clean overdoped cuprate Tl2201 and show that conventional FIB processing causes thermally driven oxygen loss, while cryogenic FIB microstructuring largely suppresses this degradation and preserves the
crystal structure from the bulk to the atomic scale. Microstructured devices quantitatively reproduce established in-plane resistivity and
Hall carrier density measurements without rescaling. Applying this approach to $c$-axis transport, we obtain absolute $\rho_c(T)$ values approximately three times larger than previously reported, bringing the transport anisotropy into quantitative agreement with the known
Fermi surface geometry within an isotropic relaxation-time approximation. These results resolve a long-standing discrepancy between transport and
quantum oscillation measurements in overdoped Tl2201 and establish cryogenic FIB microstructuring as a route to reliable quantitative transport measurements in
quantum materials where disorder, inhomogeneity, geometry, or small
crystal size have previously limited experimental accuracy.
Read the full abstract ▾
All authors Ayanesh Maiti, Carsten Putzke, Linus Holeschovsky, Roemer D. H. Hinlopen, Chunyu Guo, Dorothee Herrmann, Seunghyun Khim, Berit H. Goodge, Andre W. Tyler, Michele S. Conroy, Andreas W. Rost, Andrew P. Mackenzie, Philip J. W. Moll
Superconductivity
Pressure-induced concurrent amorphization and superconductivity in topological material NbNiTe5
Lingxiao Zhao, Yi Zhao, Bangshuai Zhu et al. (+6 more)
We have systematically studied the structural and electronic properties of a topological material NbNiTe5 under high pressure. The
evolution of the normal state resistance shows a non-monotonic trend from 0.7 GPa to 5.1 GPa, in accordance with the second-order transition along the inter-layer direction observed in X-ray diffraction and Raman spectra. At around 10 GPa, the sample starts amorphization, which is concurrent with the emergence of superconductivity. Upon further compression, the structural disorder enhances and the superconducting transition becomes clearer, suggesting that the superconductivity is modulated by the degree of disorder in NbNiTe5 under high pressure. Within 45.7 GPa, the superconducting transition temperature (Tc) slowly rises from 0.6 K at 9.5 GPa to 1.4 K at 45.7 GPa. Our findings extend the family of transition metal chalcogenide
superconductors and shed new light on understanding superconductivity in disordered systems.
Read the full abstract ▾
All authors Lingxiao Zhao, Yi Zhao, Bangshuai Zhu, Qi Wang, Cuiying Pei, Juefei Wu, Jin-Ke Bao, Wen-He Jiao, Yanpeng Qi
Mesoscale and Nanoscale Physics
Optical switching of magnetic order in few-layer CrSBr
Lukas Husel, Julian Trapp, Moritz Würf et al. (+7 more)
Manipulating magnetism with light is crucial for both fundamental understanding and technological advancements of information storage devices. The layered antiferromagnet CrSBr, part of the recently emerging class of two-dimensional van der Waals magnets, offers a unique path towards optical control of magnetism via magneto-
excitons, which allow optical readout of the
spin alignment and also provide a strong absorption channel. Here, we use
exciton absorption and photoluminescence to demonstrate optical switching of the
magnetic order in bi- and trilayer CrSBr. Using a continuous-wave
laser with a power as low as a few microwatts at near-critical external
magnetic fields, we demonstrate both local and remote switching of the
magnetic configuration in extended lateral domains and further employ this mechanism to deterministically prepare the zero-field
magnetic configuration. Our results establish optical switching as a useful means of controlling magnetism in CrSBr, with potential applications in magneto-optoelectronic devices.
Read the full abstract ▾
All authors Lukas Husel, Julian Trapp, Moritz Würf, Anna Rupp, Tim Wedl, Kenji Watanabe, Takashi Taniguchi, Iva Plutnarova, Zdenek Sofer, Alexander Högele
Materials Science
Synthesis and structural validation of close-to-stoichiometric NiTe$_2$ single crystals
T. Tirasutt, L. H. Tjeng and A. C. Komarek
We report the synthesis of stoichiometric NiTe$_{2}$ single
crystals via chemical vapor transport together with precise structural characterization. A combined analysis using powder and single
crystal X-ray diffraction (XRD) was performed to determine
lattice parameters and structural details. High-resolution single
crystal XRD reveals no evidence of interstitial nickel, confirming a close-to-stoichiometric composition. This work establishes a reliable
benchmark for the
crystal structure of stoichiometric NiTe$_{2}$, offering a reference for future studies on its physical properties.
Read the full abstract ▾
Quantum Physics
Task-Dependent Syndrome Memory in Quantum Sensing and State Recovery
Jianqi Sheng
Preserving metrological information under noise is central to
quantum sensing, yet finite detectors and
memories impose an unavoidable limit on how finely noise trajectories can be resolved. Using exact symmetric-logarithmic-derivative geometry, we determine when a monitored trajectory can be compressed without losing
quantum Fisher information. For an explicit faithful monitored
qubit family, the complete joint signal-and-noise model is recoverable from only polynomially many type records, requiring $O(\log n)$ terminal
memory, whereas deferred recovery of arbitrary $n$-
qubit states requires exponentially many trajectories, or $O(n)$
memory. Online correction replaces this terminal storage by an irreducible per-use readout and feedback alphabet. These results establish syndrome information as a task- and timing-dependent resource connecting
quantum sensing, statistical sufficiency, and
quantum error correction.
Read the full abstract ▾
Optics
Gallium phosphide on insulator for nanophotonics and quantum technologies
Tobias Bucher, Otto Arnold, Muyi Yang et al. (+7 more)
Gallium phosphide is a promising material platform for visible and near-infrared photonics and
quantum technologies owing to its high refractive index, low optical absorption, and strong second-order nonlinearity. Here, we demonstrate the fabrication of GaP-on-
insulator substrates by ion slicing. The splitting depth and exfoliation behavior of bulk GaP are tailored by controlling the He$^{+}$ ion implantation energy and fluence, enabling thin-film transfer onto amorphous substrates by anodic bonding and
plasma-enhanced direct wafer bonding. Channeling Rutherford backscattering spectrometry and X-ray diffraction confirm that the transferred layers retain their single-crystalline structure, while implantation-induced disorder and optical absorption are substantially reduced by annealing at 500 {\deg}C and subsequent polishing. The annealed films exhibit linear optical properties approaching those of bulk GaP. In addition, a (110)-oriented GaP thin film shows the characteristic polarization dependence expected from the zinc-blende second-order nonlinear susceptibility tensor, demonstrating a near-pristine second-order nonlinear response. This flexible fabrication approach enables the integration of high-quality single-crystalline GaP with variable orientation for free-space and integrated nanophotonics as well as nonlinear and
quantum optical devices.
Read the full abstract ▾
All authors Tobias Bucher, Otto Arnold, Muyi Yang, Zifei Zhang, Katsuya Tanaka, Annkathrin Köhler, Berit Marx-Glowna, Duk-Yong Choi, Isabelle Staude, Carsten Ronning
Quantum Physics
Learnable yet not simulable: a quantum resource theory of learning models
Xinbiao Wang, Yuxuan Du and Dacheng Tao
Quantum resource theory has sharpened our understanding of the intrinsic complexity of
quantum systems, particularly their classical simulability. However, it remains unclear which
quantum resource governs the classical learnability of
quantum circuits, especially beyond the regime of efficient classical simulation. Here we close this knowledge gap by studying the expectation-value functions of families of tunable
quantum circuits, with many applications in digital
quantum simulation,
quantum metrology, and
quantum-system characterization. Specifically, we introduce a new resource measure, the dynamical stabilizer
entropy (\DSE), which quantifies how broadly an expectation-value function is distributed across its frequency modes. By relating \DSE to operator stabilizer
entropy, we establish a computational phase diagram that compares classical simulators with
quantum-data-assisted classical surrogates. We first determine the \DSE-dependent learnability boundary of this diagram by deriving bounds on the sample complexity and runtime of classical surrogates, and by developing a \DSE-guided surrogate. We then complete the diagram by proving, under standard complexity-theoretic assumptions, the existence of
circuit families that can be efficiently learned by this surrogate but cannot be efficiently emulated from their
circuit descriptions alone. Numerical experiments on random and structured
circuits with up to 80
qubits support the predicted \DSE-dependent computational landscape. These results establish a quantitative resource-theoretic framework for delineating the boundary between classical simulation and learning, motivate resource measures linking
quantum resources to learnability, and guide the design of learning-based
algorithms for scalable
quantum systems beyond the reach of direct classical simulation.
Read the full abstract ▾
High Energy Astrophysical Phenomena
Magnetic rigidity reveals the PeVatron acceleration region in SS 433
Jie Liao, Wancheng Xu, Lang Cui et al. (+10 more)
PeVatrons are
cosmic accelerators capable of driving particles to petaelectronvolt (PeV) energies. Recently, microquasar jets have emerged as compelling
Galactic PeVatron candidates. This is especially the case for SS 433 as its $>100$ TeV gamma-ray emission is spatially coincident with an atomic cloud. However, the exact region where PeV
protons are accelerated and injected within these jets remains unresolved. Here we report, using archival, multi-frequency VLBA observations, the
magnetic field profile $B(H)$ along the SS 433 inner jet on tens of AU scale, where $H$ is the distance from the central compact object. We find that the field declines as $B(H) \propto H^{-0.50\pm0.12}$, demonstrating that the
magnetic rigidity $B(H)R_{\rm acc}$ grows with $H$ for a conical jet. This implies the Hillas limit ($E_{\rm max} \propto BH$) to lie well beyond a PeV at a few hundred-AU scale, which becomes a highly potential site for accelerating
protons to energies $E_{\rm cut} \simeq 2.6$ PeV inferred from the LHAASO gamma-ray spectrum. These results reveal a hidden PeVatron within the baryonic ejecta of microquasar SS 433, well upstream of the extended TeV-emitting lobes.
Read the full abstract ▾
All authors Jie Liao, Wancheng Xu, Lang Cui, Pak-Hin Thomas Tam, Xi Yan, Linuo Yang, Ruo-yu Liu, Liang Chen, Ning Chang, Yong-Feng Huang, Long Ji, Ashutosh Tripathi, Felix Aharonian
Soft Condensed Matter
Colloidal Systems
Darrell Velegol
This book has one primary goal: To get you moving quickly from learning basic principles of colloid science, to designing colloidal systems for function or motion in the lab. It is not intended to provide encyclopedic knowledge about all aspects of colloid and surface science; rather, I have chosen not to include many topics of genuine importance. In reaching the intended goal, I use two parallel strategies. First, I give practical results that can be used immediately. If there is a cumbersome calculation, I have worked to reframe it into a table or figure. This is the case for Hamaker constants and hydrodynamics of spheroids, for instance. Second, I describe the physics of various colloidal phenomena, so that you as a researcher can think about alternative strategies. In balancing
algorithms with explanations, I provide plug-and-chug example problems to familiarize you with units, constants, and typical values. The practice problems provide extensions to the most basic theory that open new possibilities, while also giving results that are useful in practical and research studies. Throughout the book, I provide data we commonly use for viscosities,
zeta potentials, ionic phenomena, and other parameters. Rather than providing every reference and every technique, I have provided those references and techniques that we most often use in our lab. In the end, this book aims not to be an exhaustive study of colloids, but rather to be a doorway to producing desired colloidal systems as quickly as possible.
Read the full abstract ▾
Soft Condensed Matter
Equilibrium gigahertz acoustics reveals long-range confinement in liquids
Ievgeniia Chaban and Thomas Pezeril
Understanding how the mechanical properties of
liquids confined within nanometer-scale gaps differ from bulk behavior is central to biophysics, lubrication, catalysis, electrochemistry, and surface science. Yet the characterization of ultrathin confined
liquids remains challenging, as many existing approaches rely on destructive or intrusive contact-based techniques, mostly measuring the
liquid flow in the low frequency regime. Here, we present a non-invasive, all-optical technique based on ultrafast
laser ultrasonics that probes confined
liquids at
equilibrium in the gigahertz frequency range. The method measures the phase and amplitude of time-domain Brillouin scattering signals transmitted through
liquid layers whose thickness is varied step by step with subnanometer effective sampling. Supported by numerical modeling of acoustic propagation and optical detection, these signals allow us to extract the thickness-dependent acoustic velocity and attenuation of confined
liquids. We show that nanometric confinement modifies the GHz acoustic response of glycerol, the
liquid crystal 8CB, and a butyl-based ionic
liquid over unexpectedly long spatial scales. These effects extend from a few nanometers to several tens of nanometers and reveal bound interfacial layers, acoustic stiffening, and enhanced solid-like behavior under confinement. Our results open a route to probing
liquid confinement in a scarcely explored regime: dynamically measured at gigahertz frequencies, yet sufficiently weakly perturbative to preserve the
equilibrium confined state.
Read the full abstract ▾
Strongly Correlated Electrons
Long and short time linear response of metals: a geometric approach
Nishchhal Verma and Raquel Queiroz
The time-dependent
quantum geometric tensor, which captures dipole fluctuations of bound electrons, is essential for understanding the electronic properties of
insulators,
superconductors, and flat bands. It is often considered subleading for low-energy descriptions of metals that are dominated by intra-band processes. Here, we revisit this perspective and highlight scenarios where the
quantum geometry of the wavefunctions close to the
Fermi surface plays a significant role. We compute the time-dependent
quantum geometric tensor for metals, explain its divergence, and contrast it against singular
geometric tensors of Dirac and Weyl semi-metals. We identify the ratio of Drude to total spectral weight, $D/\mathcal{S}_1$, as a
lattice-scale probe of bound versus itinerant charge, and quantify it in the kagome metal, where the two van Hove fillings respond differently despite identical
Fermi surfaces.
Read the full abstract ▾
Statistical Mechanics
Gabriele de Mauro, Manas Kulkarni and Satya N. Majumdar
We introduce a
quantum stochastic resetting protocol with uniform
memory, in which each resetting event returns the system to a state visited at a time chosen uniformly from its entire history. The resulting dynamics is nonunitary, non-Markovian and a direct
quantum generalization of the classical preferential relocation model. Working in the energy eigenbasis, we derive the exact
evolution of every density-
matrix element for an arbitrary time-independent
Hamiltonian and show that the
Hamiltonian enters the dynamics only through the corresponding Bohr frequencies. This leads to a natural distinction between two classes of
quantum systems: gapped and gapless. In gapped systems (systems with a discrete energy spectrum), while the diagonal elements remain unchanged, the off-diagonal elements of the density
matrix in the energy eigenbasis decay algebraically with a continuously varying exponent and with an amplitude that oscillates periodically in $\log t$. The system therefore approaches a stationary state that is independent of the resetting rate and retains a strong
memory of the initial state. In gapless systems (systems with a continuous energy spectrum), arbitrarily small Bohr frequencies prevent stationarity. Instead, the position distribution spreads on the universal (ultra-slow) scale $\log(rt)/r$, independently of the initial state and of the details of the
Hamiltonian. We illustrate these results with a two-level system, a harmonic oscillator, and a free
quantum particle, and contrast them with their classical counterparts.
Read the full abstract ▾
Astrophysics of Galaxies
XRISM Resolves the Circum-nuclear Environment of NGC 4945
Peter G. Boorman, Poshak Gandhi, Yoshihiro Ueda et al. (+31 more)
Compton-thick Active
Galactic Nuclei (AGN) represent one of the most elusive phases of massive black hole growth, yet are expected to contribute substantially to the
Cosmic X-ray Background and the integrated growth of massive black holes. NGC 4945 is the closest Compton-thick AGN and amongst the brightest AGN in the hard X-ray sky, making it an important
benchmark for more distant Compton-thick AGN. We present the first high-resolution X-ray spectral analysis of NGC 4945 using XRISM/Resolve. The entire 4-15 keV Resolve spectrum, including a strong Fe K$\alpha$ doublet and weak Compton Shoulder, is well described by a de-coupled dual-obscurer model. The model features a low-covering-factor Compton-thick primary obscurer intersecting the line-of-sight that permits the rapidly variable, direct transmitted coronal continuum to dominate above 10 keV. A Compton-thin secondary reprocessor with a high covering factor dominates the reprocessed emission between $\sim$4-10 keV. Assuming that virial motion accounts for line broadening, the secondary reprocessor can exist at $\sim$0.12 pc, and could help explain the weak high-ionisation optical and infrared emission lines observed in NGC 4945. If such obscuration geometries are common among more distant and/or fainter Compton-thick AGN, our results suggest that simpler coupled X-ray spectral modelling could substantially over-estimate Compton-thick covering factors and under-estimate intrinsic X-ray luminosities.
Read the full abstract ▾
All authors Peter G. Boorman, Poshak Gandhi, Yoshihiro Ueda, Bert Vander Meulen, Kanta Fujiwara, Aoi Nakano, Johannes Buchner, Claudio Ricci, Kirpal Nandra, Daniel Stern, Almudena Alonso Herrero, Carolina Andonie, Franz E. Bauer, Stefano Bianchi, Murray Brightman, Francesca Civano, Richard I. Davies, Gulab Dewangan, Georgios Dimopoulos, Ismael García-Bernete, Santiago García-Burillo, Sebastian F. Hönig, Nancy A. Levenson, Andrea Merloni, Yuya Nakatani, Hirofumi Noda, Shoji Ogawa, Chris Packham, Simonetta Puccetti, Cristina Ramos Almeida, Marko Stalevski, Yuichi Terashima, Martin Ward, Satoshi Yamada
High Energy Physics (Phenomenology)
The $(2+1)$-dimensional Gross-Neveu-Yukawa model at finite temperature, density, and magnetic field within the Functional Renormalization Group
Justin L.P. Mauldin and Dirk H. Rischke
We investigate the phase diagram of the (2+1)-dimensional Gross-Neveu-Yukawa (GNY) model at finite temperature, density, and
magnetic field beyond mean-field, using the Functional Renormalization Group (FRG) in the local potential approximation. Large
magnetic fields result in
magnetic catalysis, a dimensional reduction of the system, and enhancement of
chiral symmetry breaking. We employ a hydrodynamical
algorithm to solve the FRG flow equation for the effective potential, which allows for go further into the infrared region than with previously used methods. We find that the
chiral condensate exhibits non-trivial behavior in various regions of the phase diagram: several first-order phase transitions and de Haas – van Alphen oscillations at small
magnetic field and large chemical potential, as well as a critical endpoint which shifts to higher temperature with increasing
magnetic field.
Read the full abstract ▾
Quantum Physics
Effects of realistic pulse shapes in two-dimensional spectroscopy
M. Russo, R. Gilliot, A. Blech et al. (+3 more)
Two-dimensional (2D) spectroscopy is a powerful pump-pump-probe technique for revealing couplings between
quantum states and disentangling the different contributions to the optical response of a system. We present an efficient method for 2D spectroscopy simulations in the Markovian limit for the environment, capable of handling arbitrary pulse shapes and reproducing time-ordering and overlapping pulse effects, while maintaining a computational cost that scales linearly with the number of sampling points. We leverage this framework to investigate how 2D spectra are affected by spectral phase distortions and highly non-Gaussian pulse shapes, such as those produced experimentally by hollow-core fibers or non-collinear optical amplifiers. We show that realistic pulses can induce the appearance of additional spectral features, lineshape distortions and oscillating contributions in the system's dynamics. Notably, even weak temporal pulse tails arising from uncorrected high-order spectral phase terms cause visible changes in the 2D spectra. We also find that homodyne detection schemes employed in experiments can mitigate the presence of such pulse effects. These results emphasize the importance of including realistic pulses in 2D spectroscopy simulations to identify pulse-induced effects and minimize ambiguities in the interpretation of experimental data.
Read the full abstract ▾
All authors M. Russo, R. Gilliot, A. Blech, M. Joffre, C. P. Koch, H. Seiler
Instrumentation and Methods for Astrophysics
Spatial Mapping and Capacitor Trimming Developments to Improve Usable Pixel Yield in PRIMA FIRESS Kilo-Pixel Arrays
Chris Albert, Jonathon Hunacek, Hien Nguyen et al. (+12 more)
The Probe far-Infrared Mission for Astrophysics (PRIMA) will use 8 kilo-pixel kinetic inductance detector (KID) arrays in its spectrometer module. We present an improved resonant frequency to spatial position mapping system designed to preserve each array's mapping after transferring it from the mapping apparatus to the flight housing. Such a mapping is necessary for astronomical observations, and additionally allows us to
laser trim the capacitive elements of KIDs to optimize resonance separation in frequency space. This increases the operating yield by eliminating collided resonances, reduces crosstalk, and reduces the sensitivity to frequency drift over time.
Read the full abstract ▾
All authors Chris Albert, Jonathon Hunacek, Hien Nguyen, Ritoban Basu Thakur, Andrew Beyer, Charles Bradford, Peter Day, Pierre Echternach, Byeong Ho Eom, Logan Foote, Marc Foote, Steve Hailey-Dunsheath, Reinier Janssen, Elijah Kane, Henry LeDuc
High Energy Astrophysical Phenomena
Production of High Energy Neutrinos in the Coronae of Ultraluminous X-ray Sources
Norita Kawanaka and Shigeo S. Kimura
We investigate the possibility of high-energy
neutrino production in coronae associated with ultraluminous X-ray sources (ULXs) as super-Eddington accreting black holes. Adopting the disk-wind-fed corona model, we calculate
stochastic proton acceleration and the resulting
neutrino emission from the ULX corona. We first examine whether the corona can be regarded as a collisionless
plasma, which is a prerequisite for efficient non-thermal particle acceleration. We find that the collisionless condition is satisfied only when the mass
accretion rate is lower than ($\sim 5\dot{M}_{\rm Edd}$). In this regime,
protons are accelerated up to energies of a few tens of TeV and produce
neutrinos through both photomeson ($p\gamma$) and hadronuclear ($pp$) interactions. The importance of hadronuclear interactions increases with
accretion rate owing to the enhanced coronal density, resulting in broad
neutrino spectra shaped by both $p\gamma$ and $pp$ processes. We also derive a correlation between
neutrino and X-ray luminosities, ($L_{\nu,{\rm tot}} \propto L_X^{2.4}$), and estimate the
neutrino flux from nearby ULXs. We show that M82 X-1 is among the most promising targets and may be detectable at the 90% confidence level by future
neutrino observatories. These results suggest that super-Eddington accreting black holes constitute a previously unexplored class of high-energy
neutrino sources.
Read the full abstract ▾