Computational Physics · Cross-listed from quant-ph
Distance learning from projective measurements as an information-geometric probe of many-body physics
Oleksii Malyshev, Simon M. Linsel, Fabian Grusdt et al. (+3 more)
The ability of modern
quantum simulators–both digital and analogue–to generate large ensembles of single-shot projective "snapshots" has opened a data-rich avenue for the study of
quantum many-body systems. Unsupervised machine learning analysis of such snapshots has gained traction, with numerous works reconstructing phase diagrams by learning and clustering low-dimensional representations of
quantum states. Here, we forgo such representation learning in favour of distance learning: we infer the pairwise distances between
quantum states–already sufficient for clustering–directly from snapshots. Specifically, we use a single neural discriminator to estimate Csiszar f-divergences–statistical distances between distributions–in an unsupervised manner. The resulting clusters reveal regimes with different dominant correlations, often coinciding with, but not limited to, conventionally defined phases of matter. Beyond phase-diagram exploration, we connect the infinitesimal limit of the inferred divergences to the Fisher information metric and analyse its finite-size scaling. This yields critical exponents of the discovered transitions and enables snapshot-based analysis of universality classes. We apply distance learning to a diverse set of systems characterised by conventional local order parameters (1D transverse-field and 2D classical Ising models), non-local topological order (extended toric code), and higher-order correlations (fermionic t-J model on a triangular
lattice). In all cases, we correctly recover boundaries between distinct correlation regimes and, where applicable, quantitatively match established critical behaviour. Finally, we show that distances to suitably chosen reference snapshot distributions help identify the dominant correlations within the discovered clusters, positioning distance learning as a versatile information-
geometric probe of
quantum many-body physics.
Read the full abstract ▾
All authors Oleksii Malyshev, Simon M. Linsel, Fabian Grusdt, Annabelle Bohrdt, Eugene Demler, Ivan Morera
Optics · Cross-listed from quant-ph
Chip-Scale Transmitter Module for Real-Time Continuous-Variable QKD
Igor Servello, Martin Hauer, Moritz Baier et al. (+6 more)
Continuous-variable
quantum key distribution (CV-QKD) enables secure communication over standard telecom infrastructure, but scaling is stalled by bulky, discrete optical hardware. We address this bottleneck by demonstrating a real-time CV-QKD system driven by a chip-scale hybrid transmitter using commercial telecom components. Combining a micro-optic external-cavity
laser with a monolithic photonic integrated IQ modulator we enable secure secret-key generation over 102 km of optical fiber while reducing optical volume by 95% relative to the commercial discrete-component counterpart. Moreover, real-time operation overcomes offline post-processing bottlenecks of experimental setups. This work bridges laboratory demonstrations and field-deployable technology for cost-effective
quantum networks.
Read the full abstract ▾
All authors Igor Servello, Martin Hauer, Moritz Baier, Emmeran Sollner, Peter Gleißner, Sebastian Randel, Ulrich Eismann, Emanuel Eichhammer, Imran Khan
Biological Physics · Cross-listed from cond-mat.stat-mech
Does Partial Consumption Help Foraging?
Md Aquib Molla and Sanchari Goswami
In this work, we consider partial consumption of food by a forager in presence of a threshold energy level. The forager considered here can survive for $S$ steps without food, namely the survival time. The threshold limits the consumption of food in such a way that, the forager will only consume food, whenever its energy is below the threshold $k$. Due to partial consumption of food, a site containing food may not always be fully depleted, which in turn helps in increasing the lifetime of the forager. It has been observed that, in our case, the lifetime always increases with $k/S$, although there is a transition threshold $k^*$ below which the increase of lifetime is rapid and above is slow. The transition threshold $k^* \sim \sqrt{S}$. The lifetime $\tau$ shows a power law behavior as $\tau \sim S^{\beta}$. For $k/S=0$, the value of $\beta$ is $1.331$, it then jumps above $2$ and decreases gradually to $1.833$ with increasing $k/S$. Other important quantities like number of revisits to a site, food statistics etc. have been studied and some interesting scaling behaviors are observed. Although, survival for each time unit requires, on an average, the consumption of one unit of food, the food consumption is not the only factor to control the lifetime of the forager. It has been observed that, the strategy in terms of threshold energy and partial consumption affects the lifetime in a positive way. The collection of sites either fully or partially depleted of food after the death of the forager shows a crossover behavior for $k/S \sim 0.5$.
Read the full abstract ▾
Computational Physics · Cross-listed from quant-ph
Hadamard regularization of open quantum systems coupled to unstructured environments in the Schwinger-Keldysh formalism
Jakob Dolgner
The theory of open
quantum systems addresses how coupling to external degrees of freedom modifies observables and
quantum coherence, a situation central to fundamental condensed-matter research and emerging
quantum technologies. Schwinger-Keldysh field theory is a natural framework for both open- and nonequilibrium
quantum systems in terms of functional integrals. However, its numerical solution is limited by a cubic scaling with the number of time steps. This is particularly prohibitive for scenarios with widely separated time scales, as is often the case for system and environmental scales. We consider a damped
quantum harmonic oscillator as a toy model to study a separation-of-scales ansatz based on Hadamard regularization. A time-stepping
algorithm for the Kadanoff-Baym equations on the slow system time-scale is presented that captures both low-temperature non-Markovianity and renormalization effects arising from the much faster environment scale.
Read the full abstract ▾
Instrumentation and Detectors · Cross-listed from quant-ph
Characterization of Radiation-Induced Errors in Superconducting Qubits Protected with Various Gap-Engineering Strategies
H. Douglas Pinckney, Thomas McJunkin, Alan W. Hunt et al. (+26 more)
Impacts from high-energy particles cause correlated errors in superconducting
qubits by increasing the quasiparticle density in the vicinity of the Josephson junctions (JJs). Such errors are particularly harmful as they cannot be easily remedied via conventional error correcting codes. Recent experiments reduced correlated errors by making the difference in superconducting gap energy across the JJ larger than the
qubit transition energy. In this work, we assess gap engineering near the JJ ($\delta\Delta_{\mathrm{JJ}}$) and the capacitor/ground-plane ($\delta\Delta_{\mathrm{M1}}$) by exposing arrays of transmon
qubits to two sources of radiation. For $\alpha$-particles from an $^{241}$Am source, we observe $T_1$ errors correlated in space and time, supporting a hypothesis that hadronic
cosmic rays are a major contributor to the $10^{-10}$ error floor observed in Ref. 1. For electrons from a pulsed linear accelerator, we observe temporally correlated $T_1$ and $T_2$ errors, this measurement is insensitive to spatial correlations. We observe that the severity of correlated $T_1$ errors is reduced for
qubit arrays with a greater degree of gap engineering at the JJ. For both $T_1$ and $T_2$ errors, the recovery time is hastened by an increased $\delta\Delta_{\mathrm{M1}}$, which we attribute to the trapping of quasiparticles into the capacitor/ground-plane. We construct a model of quasiparticle dynamics that qualitatively agrees with our observations. This work reinforces the multifaceted influence of radiation on superconducting
qubits and provides strategies for improving radiation resilience.
Read the full abstract ▾
All authors H. Douglas Pinckney, Thomas McJunkin, Alan W. Hunt, Patrick M. Harrington, Hannah P. Binney, Max Hays, Yenuel Jones-Alberty, Kate Azar, Felipe Contipelli, Renée DePencier Piñero, Jeffrey M. Gertler, Michael Gingras, Aranya Goswami, Cyrus F. Hirjibehedin, Mingyu Li, Mathis Moes, Bethany M. Niedzielski, Mallika T. Randeria, Ryan Sitler, Matthew K. Spear, Hannah Stickler, Jiatong Yang, Wouter Van De Pontseele, Mollie E. Schwartz, Jeffrey A. Grover, Kevin Schultz, Kyle Serniak, Joseph A. Formaggio, William D. Oliver
Physics Education · Cross-listed from hep-ph
Ultralight Dark Matter: Undergraduate Physics in Modern Cosmology
Timothy D. Wiser
Ultralight dark matter is a hypothetical class of particle with a number of interesting theoretical and experimental properties, many of which are best understood by direct analogy with or application of undergraduate physics. We present a series of exercises and discussions which may inspire the reader to bring contemporary research on ultralight dark matter into the undergraduate classroom.
Read the full abstract ▾
Classical Physics
Zeeman effect in hydrogen treated in classical physics with classical zero-point radiation
Timothy H. Boyer
The Zeeman effect for the low resonant energy states of hydrogen is treated with classical electrodynamics including classical zero-point radiation. The electron is regarded as a classical charged particle in a Coulomb potential. The "space quantization" of old
quantum theory, the Sommerfeld relativistic result, and the Stern-Gerlach experiment are all considered.
Read the full abstract ▾
Classical Physics
Relativistic hydrogen in classical electrodynamics with classical zero-point radiation
Timothy H. Boyer
Classical electrodynamics including classical electromagnetic zero-point radiation leads to a ground state and resonant excited states for a charged particle in a Coulomb potential. These resonant states correspond to integer values of the action variables analogous to those appearing in the Bohr-Sommerfeld theory of the hydrogen atom. The work on classical zero-point radiation reported here is a continuation of the analysis reported in 1975, but with the addition of the ideas of relativity and resonance between the charged-particle orbit and classical zero-point radiation.
Read the full abstract ▾
Classical Physics
Classical linear oscillator in classical electrodynamics with classical zero-point radiation
Timothy H. Boyer
A classical linear oscillator is treated in the small amplitude limit so that it will be approximately relativistic. The oscillator involves a charge particle in a linear potential in classical zero-point radiation. It is found that the ground state is energy balanced with the power lost in radiation emission equal to the average power gained from resonance with the classical zero-point radiation. Also the oscillator is found to have resonant excited states where the energy emitted as dipole radiation is balanced on average by the energy gained from the zero-point radiation when the action variable of the mechanical system is given by J=(n+1/2)(h/2pi).
Read the full abstract ▾
Instrumentation and Detectors
Development of a high-field pulsed magnet and optical fiber coupled cryostat system for magneto-photoluminescence measurements
Deepesh Kalauni, Kingshuk Mukhuti, Tao Peng et al. (+1 more)
This paper presents the development of a high field pulsed magnet system combined with an optical fiber-coupled low temperature cryostat for magneto-photoluminescence measurements. A novel aspect of our system is the use of electrolyte capacitors in a 75 kJ capacitor bank to drive the pulsed magnet, enabling the generation of high
magnetic fields at a relatively low charging voltage (400 V). The zylon reinforced wire wound magnet coil achieves a maximum field strength of 35 tesla with a
magnetic field rise time of 10 ms. The integrated cryostat was developed to meet the specific requirements of magneto-photoluminescence experiments using a 4 K helium closed-cycle cryocooler to provide a stable low-temperature environment down to 5 K.
Read the full abstract ▾
All authors Deepesh Kalauni, Kingshuk Mukhuti, Tao Peng, Bhavtosh Bansal
Geophysics · Cross-listed from cs.LG
Self-Flow-Matching assisted Full Waveform Inversion
Xinquan Huang and Paris Perdikaris
Full-waveform inversion (FWI) is a high-resolution seismic imaging method that estimates subsurface velocity by matching simulated and recorded waveforms. However, FWI is highly nonlinear, prone to cycle skipping, and sensitive to noise, particularly when low frequencies are missing or the initial model is poor, leading to failures under imperfect acquisition.
Diffusion-regularized FWI introduces generative priors to encourage geologically realistic models, but these priors typically require costly offline pretraining and can deteriorate under distribution shift. Moreover, they assume Gaussian initialization and a fixed noise schedule, in which it is unclear how to map a deterministic FWI iterate and its starting model to a well-defined
diffusion time or noise level. To address these limitations, we introduce Self-Flow-Matching assisted Full-Waveform Inversion (SFM-FWI), a physics-driven framework that eliminates the need for large-scale offline pretraining while avoiding the noise-level
alignment ambiguity. SFM-FWI leverages flow matching to learn a transport field without assuming Gaussian initialization or a predefined noise schedule, so the initial model can be used directly as the starting point of the dynamics. Our approach trains a single flow network online using the governing physics and observed data. At each outer iteration, we build an interpolated model and update the flow by backpropagating the FWI data misfit, providing self-supervision without external training pairs. Experiments on challenging synthetic
benchmarks show that SFM-FWI delivers more accurate reconstructions, greater noise robustness, and more stable convergence than standard FWI and pretraining-free regularization methods.
Read the full abstract ▾
Chemical Physics
A Conceptual Shift In Our Understanding of Degenerate Radical Spin Systems: Spin-Rotation Coupling Turned On Its Head
Linqing Peng, Titouan Duston, Nadine Bradbury et al. (+4 more)
For most chemists, Kramers' degeneracy refers to the fact that for any radical system, every potential energy surface is at least doubly degenerate (with
spin up and
spin down, time-reversed solutions) for all
nuclear positions $\mathbf{X}$. That being said, as is well-known to the community of
spin chemists, one can experimentally detect a splitting of almost every rotational energy level for a doublet system – highlighting the fact that
nuclear motion breaks the
spin degeneracy of such BO electronic states. Thus, as far as predicting experimental spectra, the implications of BO degeneracy are very limited unless one further includes a complete treatment of
nuclear-electronic
entanglement in a robust fashion; indeed, understanding radical molecules (and the degeneracy of their stationary states) can be extremely non-intuitive within the paradigm of Born-Oppenheimer potential energy surfaces. Now, as an alternative to BO theory, recent theory has suggested characterizing radical potential energy surfaces as functions of both
nuclear position $\mathbf{X}$ and
nuclear momentum $\mathbf{P}$, an approach which has been shown to recover a host of observables outside of BO theory, e.g., vibrational circular dichroism, Raman optical activity, and lambda doubling. Here, we show that such a technique predicts that different
spin states will follow different (nondegenerate) potential energy surfaces and that the differences in these
spin-dependent surfaces is quantitatively consistent with experimental
spin-rotation couplings – all without any contradiction with regard to Kramers' degeneracy. Thus, the present finding suggests there is still a great deal to learn about
spin-resolved molecular reactivity, demanding a conceptual shift in our understanding of coupled
spin-
nuclear motion, especially in the context of
chiral molecules and materials where
spin-separation is known to arise.
Read the full abstract ▾
All authors Linqing Peng, Titouan Duston, Nadine Bradbury, Mansi Bhati, Xuecheng Tao, Michael Rosen, Joseph E. Subotnik
Computational Physics · Cross-listed from math.NA
Mode veering and symmetry-protected crossings in conservative elastic waveguides: unified perturbation-theoretic interpretation and adaptive tracking
Dong Xiao, Zahra Sharif-Khodaei and M.H. Aliabadi
Accurate mode tracking is essential for elastic waveguide dispersion analysis in ultrasonic nondestructive evaluation and structural health monitoring. Its reliability, however, deteriorates near mode veering and closely spaced
eigenvalues, where rapid eigenvector exchange causes mode misidentification. Although widely observed, the quantitative relationship between veering, eigenvector
evolution, and tracking robustness has not been systematically established. By specializing classical perturbation theory to the single-parametric Hermitian SAFE eigenproblem–exemplified by conservative elastic waveguides–we obtain explicit expressions for eigenvector derivatives and modal coupling strength. This yields a unified, quantitative interpretation of mode veering,
symmetry-protected crossings, and degeneracies, and clarifies their distinct tracking implications: eigenvector sensitivity scales inversely with the eigengap, explaining modal repulsion and the degradation of correlation-based tracking near avoided crossings, whereas
symmetry-protected crossings remain benign because
symmetry-induced decoupling preserves smooth eigenvector
evolution, and
symmetry-protected degeneracies require rotation-invariant subspace tracking. A numerical consistency condition and an existence result for a critical step size are then derived, motivating a two-level adaptive strategy with an a posteriori error indicator that separates numerical tracking consistency from
symmetry-based physical correctness. Numerical examples validate the theoretical predictions and demonstrate improved robustness in regions of strong modal interaction, providing practical guidance for reliable dispersion calculations and ultrasonic inspection.
Read the full abstract ▾
Computational Physics
From Experiments to Expertise: Scientific Knowledge Consolidation for AI-Driven Computational Physics
Haonan Huang
While large
language models (LLMs) have transformed AI
agents into proficient executors of computational materials science, performing a hundred simulations does not make a researcher. What distinguishes research from routine execution is the progressive accumulation of knowledge - learning which approaches fail, recognizing patterns across systems, and applying understanding to new problems. However, the prevailing paradigm in AI-driven computational science treats each execution in isolation, largely discarding hard-won insights between runs. Here we present QMatSuite, an open-source platform closing this gap.
Agents record findings with full provenance, retrieve knowledge before new calculations, and in dedicated reflection sessions correct erroneous findings and synthesize observations into cross-compound patterns. In
benchmarks on a six-step
quantum-mechanical simulation workflow, accumulated knowledge reduces
reasoning overhead by 67% and improves accuracy from 47% to 3% deviation from literature - and when transferred to an unfamiliar material, achieves 1% deviation with zero pipeline failures.
Read the full abstract ▾
Optics · Cross-listed from cond-mat.mes-hall
Unified Theory of Spin and Orbital Inverse Faraday Effects in Rashba Metals
Jaglul Hasan, Maxim Dzero and Chandan Setty
The inverse Faraday effect (IFE) offers a promising route toward optical control of
magnetic moments in
quantum materials. Yet experiments on
spin-orbit-coupled metals indicate that no single microscopic mechanism suffices, implicating orbital currents alongside
spin polarization. We derive both responses in a disordered Rashba metal using
quantum kinetics and diagrammatics with
impurity-renormalized optical vertices, providing the first unified diagrammatic derivation of
spin and orbital IFE. Treating
impurity scattering consistently, our number-conserving kinetic formulation restores full phase-space derivatives and the optical
magnetic field neglected in earlier treatments. We connect nonlinear orbital magnetization to absorptive linear optical conductivity, revealing that the
magnetic Lorentz force supplies half the orbital response. Our unified treatment resolves both channels across the Rashba resonance:
spin IFE changes sign as frequency increases, while the orbital IFE dominates, keeping the direction of the total magnetization unchanged.
Read the full abstract ▾
Applied Physics · Cross-listed from quant-ph
Fluxon Time-Delay Readout of a Superconducting Qubit Protected by a Spectral Gap in a Josephson Transmission Line
Shunsuke Kamimura, Aree Taguchi, Masamitsu Tanaka et al. (+1 more)
We theoretically investigate a readout scheme of the
quantum state of a superconducting
qubit based on time delay of a single flux
quantum (SFQ), also known as a fluxon, propagating in a Josephson transmission line (JTL). We concretely study the time-delay readout based on capacitive coupling between a transmon
qubit and a JTL, and we evaluate the time delay depending on the
qubit state. We also reveal a feature of the absence of fluxon pinning and exponential suppression of nonadiabatic transitions caused by the propagating fluxon, which is advantageous for the time-delay readout. We extend the analysis to a multi-level transmon as well. Owing to the spectral gap in the JTL, the radiative decay of the
qubit mediated by the JTL is exponentially suppressed, and thus the transmission line itself also serves as a filter protecting the
qubit. The readout scheme requires neither complicated wiring to low-temperature stages nor bulky microwave components, which are bottlenecks for integration of a large-scale superconducting
quantum computer.
Read the full abstract ▾
All authors Shunsuke Kamimura, Aree Taguchi, Masamitsu Tanaka, Tsuyoshi Yamamoto
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Zinc selenide single crystals co-doped with active TM-ions of chromium, cobalt and iron
Sergei Naydenov, Oleksii Kapustnyk, Igor Pritula et al. (+1 more)
The development of
laser materials with absorption/emission spectra in the atmospheric transparency band 2-5 microns is of great interest for modern applications. Triple-doped zinc selenide
crystals activated with chromium, cobalt, and iron ions were grown by the vertical Bridgman method under high argon pressure. Comparative X-ray diffractometry, infra-red spectroscopy, and other studies of grown
crystals were conducted. Features of their growth, morphology, and optical properties related to the
crystal structure were discovered.
Read the full abstract ▾
All authors Sergei Naydenov, Oleksii Kapustnyk, Igor Pritula, Dmitro Sofronov
Chemical Physics · Cross-listed from quant-ph
Resource-efficient Quantum Algorithms for Selected Hamiltonian Subspace Diagonalization
Vincent Graves, Manqoba Q. Hlatshwayo, Theodoros Kapourniotis et al. (+1 more)
Quantum algorithms for selecting a subspace of
Hamiltonians to diagonalize have emerged as a promising alternative to variational
algorithms in the NISQ era. So far, such
algorithms, which include the
quantum selected configuration interaction (QSCI) and sample-based
quantum diagonalization (SQD), have been formulated within second-quantization in Fock space, which leads to inefficient usage of
qubit resources. We introduce the first QSCI
algorithm developed in the CI-
matrix (CIM) framework, which is known to have optimal
qubit scaling of exactly $\lceil \log_2 (N) \rceil$ where $N$ is the size of the CIM. In addition, we introduce a novel single-bit flip error mitigation which comes at the overhead of a single
qubit and we combine this with a
stochastic approximate Trotterization
evolution adapted from qDRIFT. Simulating
benchmark N$_2$ and naphthalene molecules on
quantum hardware, our results achieved similar accuracy as SQD methods but with significantly less
quantum resources. However, our CIM-QSCI
algorithm and SQD methods could not match the performance of classical heat-bath CI (HCI) for the same task. Hence, we introduce an augmented version of QSCI called
quantum selected heat-bath CI (QSHCI). This variant replaces classical heat-bath sampling with
quantum sampling from QSCI to achieve performance comparable to HCI. We note that a current drawback of our approach is the preprocessing cost of $\mathcal{O}(N^2\log N)$ for constructing the CIM and performing the Pauli decomposition. This can be further improved by considering efficient CIM access models for the
stochastic Trotter
evolution.
Read the full abstract ▾
All authors Vincent Graves, Manqoba Q. Hlatshwayo, Theodoros Kapourniotis, Konstantinos Georgopoulos
Applied Physics · Cross-listed from math.PR
Clustering without geometry in sparse networks with independent edges
Alessio Catanzaro, Remco van der Hofstad and Diego Garlaschelli
The coexistence of sparsity and clustering (non-vanishing average fraction of triangles per node) is one of the few structural features that, irrespective of finer details, are ubiquitously observed across large real-world networks. This fact calls for generic models producing sparse clustered graphs. Earlier results suggested that sparse random graphs with independent edges fail to reproduce clustering, unless edge probabilities are assumed to depend on underlying metric distances that, thanks to the triangle inequality, naturally favour triadic closure. This observation has opened a debate on whether clustering implies (latent) geometry in real-world networks. Alternatively, recent models of higher-order networks can replicate clustering by abandoning edge independence. In this paper, we mathematically prove, and numerically confirm, that a sparse random graph with independent edges, recently identified in the context of network renormalization as an invariant model under node aggregation, produces finite clustering without any
geometric or higher-order constraint. The underlying mechanism is an infinite-mean node fitness, which also implies a power-law degree distribution. Further, as a novel phenomenon that we characterize rigorously, we observe the breakdown of self-averaging of various network properties. Therefore, as an alternative to geometry or higher-order dependencies, node aggregation invariance emerges as a basic route to realistic network properties.
Read the full abstract ▾
Applied Physics
MgB$_2$ Thermal Kinetic Inductance Detector
T. Jabbari, A. Hawkins, A. Wandui et al. (+6 more)
Thermal Kinetic Inductance Detectors (TKIDs) inherently combine the
phonon-limited noise performance of traditional bolometers with the array scalability and responsivity of superconducting kinetic inductance detectors. Using a superconducting resonator as the thermally sensitive element provides high responsivity and tunable dynamic range, with
phonon noise set by the cryogenic operating temperature of the free-standing membrane. In this work, MgB$_2$-based TKIDs are demonstrated operating from below 1 K up to 20 K with characterized noise-equivalent power (NEP) using integrated on-membrane heaters. A comprehensive characterization of electrical, thermal, and noise properties is presented.
Phonon noise-limited performance is demonstrated from 4 to 8 K.
Read the full abstract ▾
All authors T. Jabbari, A. Hawkins, A. Wandui, C. Frez, J. Greenfield, C. Roberson, M.J. Lee, P. Mauskopf, D. Cunnane
Instrumentation and Detectors
Charge-Carrier transport simulations in diamond detectors with electric-field-dependent mobility and charge-collection-distance-based trapping
Faiz Rahman Ishaqzai, Muhammed Deniz, Marta Baselga Baselga et al. (+4 more)
Diamond detectors are attractive for operation in harsh radiation environments because they combine radiation tolerance, fast signal formation, and low leakage current. Realistic detector-response simulations require an accurate description of charge-carrier mobility and trapping, which determine both signal amplitude and timing. In this work, we extend \allpix{}, a modular end-to-end detector simulation framework, with diamond-specific transport models. The implementation includes field-dependent mobility parameterizations for electrons and holes and an effective trapping model based on the charge collection distance (CCD), providing a detector-level interface to material quality and radiation-damage measurements. The mobility description is validated in the negligible-trapping limit using single-crystalline CVD diamond by comparing simulated drift velocities and transient-current signals with published reference data. For polycrystalline CVD diamond, the CCD-based trapping model is evaluated using experimentally measured CCD values and compared with laboratory transient-current-technique waveforms. The simulations reproduce the measured drift-velocity behavior in scCVD and the reduced charge collection and degraded transient response observed in pcCVD. The presented implementation enables detector-level studies of charge collection, pulse formation, and timing performance in diamond sensors using experimentally accessible transport and trapping parameters, and provides a practical framework for simulation-driven detector development and radiation-damage studies.
Read the full abstract ▾
All authors Faiz Rahman Ishaqzai, Muhammed Deniz, Marta Baselga Baselga, Tobias Bisanz, Kevin Kröninger, Jens Weingarten, Antonia Wippermann
Optics · Cross-listed from quant-ph
Robustness and optimization of N00N-state interferometry
Romain Dalidet, Anthony Martin, Louis Bellando et al. (+4 more)
Quantum-enhanced interferometry is often discussed in terms of ideal resources and asymptotic scalings, whereas in practice its performance is set by a delicate interplay between losses, state imbalance, and
photon number. We address this interplay in a folded Franson interferometer fed with partially entangled N00N states, treating asymmetric losses and tunable input imbalance on equal footing. From exact detection probabilities we obtain closed-form expressions for the fringe visibility and the Fisher information, and show that these two figures of merit respond very differently to imperfections. In particular, we demonstrate that perfect interference contrast can always be recovered by compensating loss asymmetry with an appropriate input imbalance, while the Fisher information generally peaks at a distinct operating point, reflecting the irreducible trade-off between coherence restoration and signal attenuation. By determining the exact optima and benchmarking against single-
photon strategies, we identify the critical loss and minimum
entanglement required to maintain a genuine
quantum advantage over optimized single-
photon strategies under identical loss conditions, and establish their scaling with the
photon number N . Beyond delineating the fundamental trade-offs between loss,
entanglement, and sensitivity, this work establishes a comprehensive theoretical framework that both underpins and extends the experimental demonstration of
quantum advantage reported in [1], providing a unified description of the relevant operating regimes.
Read the full abstract ▾
All authors Romain Dalidet, Anthony Martin, Louis Bellando, Mathieu Bellec, Nicolas Fabre, Sébastien Tanzilli, Laurent Labonté
Plasma Physics
Comprehensive full-f drift-kinetic and delta-f gyrokinetic simulations of a linear plasma device based on the gyro-moment approach
Jacob Emil Mencke and Paolo Ricci
First of a kind comprehensive full-f drift-kinetic (DK) and $\delta$-f gyrokinetic (GK) turbulent simulations are carried out in a linear
plasma device. We self-consistently derive an electrostatic model including large-scale slowly-varying DK-ordered fields coupled to small-scale rapidly-fluctuating GK-ordered fields. By relying on the critical balance ordering, we show that the electrons are described by a drift-reduced Braginskii model while we rely on a Hermite-Laguerre spectral expansion for describing both the DK and GK parts of the ion distribution function. Global simulations are carried out using the parameters of the linear device LAPD, showing that the DK part of the ion distribution function is approximately a bi-Maxwellian. Fast spectral convergence both for the DK and GK Hermite-Laguerre expansion coefficients is observed, and that the GK fields do not affect the DK fields at the physical LAPD collisionality. Only when the collisionality is reduced and the source term is amplified for the GK fluctuations, an amplification of small-scale turbulent structures is observed. The findings are supported by linear results that show that the simulations are dominated by turbulent fluctuations that are Kelvin-Helmholz driven. Additionally, a GK Kelvin-Helmholz-like mode is observed in the low-GK-collisionality regime which can non-linearly drive small-scale structures.
Read the full abstract ▾
Applied Physics · Cross-listed from cond-mat.mtrl-sci
Rate-Dependent Reversibility and Lithium Losses in Hybrid Anode-Collector Metal Electrodes
Arturo Galindo, Jesus Diaz-Sanchez, Sunil Kumar et al. (+5 more)
Understanding how practical lithium storage capacity varies with charge-discharge rate is crucial for designing durable anode free lithium batteries. We examine the lithiation behavior of single element metal electrodes-Al (alloying), Mg (solid solution intercalation), Ag (solid solution then alloying), and Cu (surface Li plating)-to determine how their mechanisms influence reversibility, measured by coulombic efficiency. Using electrochemistry combined with depth resolved ion beam profiling, we map local coulombic efficiency across current densities and identify dominant lithium loss pathways. Ag uniquely sustains fast kinetics and high reversibility at elevated rates due to rapid formation of gamma brass-type
alloy phases. In contrast, Mg and Al show increasing irreversibility from kinetically or structurally driven Li trapping, while Cu exhibits the largest losses through porous, highly reactive plated lithium. These results reveal fundamental limits of anode free systems that depend on reversible Li plating without excess lithium and underscore the importance of metal selection for stable, high rate performance.
Read the full abstract ▾
All authors Arturo Galindo, Jesus Diaz-Sanchez, Sunil Kumar, Bouthayna Alrifai, Andrea Marchetti, Gaston Garcia, Celia Polop, Enrique Vasco
Chemical Physics · Cross-listed from quant-ph
Is the matrix completion of reduced density matrices unique?
Gustavo E. Massaccesi, Ofelia B. Oña, Luis Lain et al. (+4 more)
Reduced density
matrices are central to describing observables in many-body
quantum systems. In electronic structure theory, the two-particle reduced density
matrix (2-RDM) suffices to determine the energy and other key properties. Recent work has used
matrix completion, leveraging the low-rank structure of RDMs and approximate theoretical models, to reconstruct the 2-RDM from partial data and thus reduce computational cost. However,
matrix completion is, in general, an under-determined problem. Revisiting Rosina's
theorem [M. Rosina, Queen's Papers on Pure and Applied Mathematics No. 11, 369 (1968)], we here show that the
matrix completion is unique under certain conditions, identifying the subset of 2-RDM elements that enables its exact reconstruction from incomplete information. Building on this, we introduce a hybrid
quantum-
stochastic algorithm that achieves exact
matrix completion, demonstrated through applications to the
Fermi-Hubbard model.
Read the full abstract ▾
All authors Gustavo E. Massaccesi, Ofelia B. Oña, Luis Lain, Alicia Torre, Juan E. Peralta, Diego R. Alcoba, Gustavo E. Scuseria
Fluid Dynamics
The Reynolds-Averaged Vortex Force Map Method
Matteo Liguori, Zhan Zhang, Francesco Ciriello et al. (+1 more)
Vortex-force mapping (VFM) links vortical flow structures to aerodynamic forces through compact-domain integrals weighted by geometry-only Laplace potentials, but existing formulations are tied to simple geometries and laminar flows. In this study, we derive a Reynolds-averaged
vortex force map (RA-VFM) directly from the incompressible Reynolds-averaged Navier-Stokes (RANS) equations, augmenting the classical
vortex-pressure (VP) term with a Reynolds-stress (RS) contribution based on the Laplace-potential-weighted divergence of the modelled Reynolds stress (Boussinesq eddy-viscosity form). The resulting framework reconstructs mean lift and drag from RANS mean fields while retaining spatial attribution of force production to specific regions and coherent structures within a compact control volume. We apply RA-VFM to unsteady RANS ($k$-$\omega$ SST) simulations of a realistic gliding goshawk with strong three-dimensionality and a matched GOE803 aerofoil section. For the aerofoil, the VP term alone reproduces the CFD force curves over the pre- and near-stall range, with RS contributions becoming appreciable only in deep stall. For the bird, by contrast, the VP term underpredicts both $C_L$ and $C_D$, whereas including the RS term reduces the mean absolute error relative to CFD from $6\%$ to $2\%$ in lift and from $5\%$ to $1\%$ in drag over an angle of attack range of $0^\circ$-$20^\circ$. RA-VFM thus extends
vortex-force mapping to turbulent, 3-D RANS flows and enables quantitative attribution of mean lift and drag to specific coherent structures within compact domains.
Read the full abstract ▾
All authors Matteo Liguori, Zhan Zhang, Francesco Ciriello, Juan Li
Applied Physics · Cross-listed from nlin.PS
Transition Waves for Energy Trapping and Harvesting
Sneha Srikanth and Andres F. Arrieta
The presence of multiple stable states and associated nonlinear phenomena, such as hysteresis, in multistable mechanical metamaterials enables frequency-independent energy harvesting and shock absorption. This study focuses on shock absorption achieved by locking transition waves to trap energy at designed locations within a multistable metamaterial. We further demonstrate that the same system can simultaneously harvest energy from impact loading, thereby exhibiting multifunctionality. The model of the multistable metamaterial is a one-dimensional chain of bistable units whose transition wave dynamics are related to topological solitary waves governed by the $\phi^4$ equation. This connection enables analytical estimation of critical design parameters required for energy trapping and also the amount of energy trapped. Numerical simulations and experiments show that trapping energy in transition waves leads to enhanced damping performance compared to corresponding linear metamaterials. We further propose design variations to increase the amount of energy trapped in the transition wave. Additionally, we identify energy splitting as a damping mechanism that arises when there are repeated impulses or a single high-amplitude impulse that generates multiple transition waves. The transition waves interact to produce localized, fast-dissipating breathers, leading to a damped response. Furthermore, experiments demonstrate that multistable metamaterials can simultaneously achieve improved energy harvesting and better damping performance compared to their linear counterparts. Together, these results highlight the use of transition waves for creating multifunctional multistable metamaterials.
Read the full abstract ▾
Fluid Dynamics
Dipolar solvent contributions for transient nanoscale electroosmotic flow
Pramodt Srinivasula
Electrohydrodynamic flows of electrolytes with low to moderate ion concentration at the nanoscale are significantly influenced by the molecular structure of water-like polar solvents within the electric double layer (EDL). Moreover, unlike in microfluidics, at these length scales the time scale of
evolution of EDL often becomes comparable to the consequent fluidic phenomena of interest. While continuum descriptions to model such phenomena typically assume a constant dielectric and viscous solvent background, this study incorporates dipolar solvent physics. Specifically, both dielectric saturation and the viscoelectric effect are implemented together into a Poisson-Nernst-Planck-Stokes framework, using the Langevin-Bikerman solvent permittivity distribution and empirical viscoelectric coefficients, respectively. Numerical simulations in a one-dimensional geometry reveal substantial modifications to the electrohydrodynamic body force density and transient electroosmotic mobility during EDL
evolution. The magnitude and temporal
evolution of these corrections are characterized across parametric regimes, revealing systematic departures from standard constant-permittivity and constant-viscosity models, with electroosmotic mobility reductions of up to 65% governed by a characteristic dimensionless parameter. The results predict a characteristic frequency-dependent transition in electroosmotic mobility and dipolar solvent corrections in emerging MHz AC electrokinetic flows. The results provide a solvent-consistent continuum framework for transient nanoscale electroosmotic flows and quantify the impact of molecular solvent structure on electrohydrodynamic transport relevant to modern nanofluidic applications.
Read the full abstract ▾
Atomic Physics · Cross-listed from quant-ph
Constraint-native quantum control for fidelity–complexity trade-offs with inexact proximal ADMM
Ziwen Song
Quantum-control pulses are often optimised for nominal fidelity before waveform constraints are imposed. This sequence can conceal the fidelity cost of producing smooth, band-limited, and amplitude-admissible controls. Here, we evaluate a constraint-native alternative based on inexact proximal alternating-direction updates. The formulation combines gate-infidelity minimisation with amplitude bounds,
Fourier-domain bandwidth projection, amplitude sparsity, and total-variation regularisation. We compare it with GRAPE, standard Krotov optimisation, and L-BFGS-B on a single-
qubit gate, a leakage-prone qutrit gate, and a two-
qubit entangler without a directly controlled target generator. Random seeds are paired across methods, and qutrit computational-subspace fidelity is reported alongside leakage. PADMM-Warm reached mean qutrit and two-
qubit fidelities of $0.6363$ and $0.9541$, respectively, while reducing total variation by factors of $13.2$ and $10.7$ relative to L-BFGS-B. These results define a reproducible fidelity–complexity trade-off, not a universal fidelity advantage. The method is therefore a numerical tool for exploring low-complexity control frontiers rather than a replacement for unconstrained high-fidelity solvers.
Read the full abstract ▾
Medical Physics · Cross-listed from eess.IV
Accelerating Stroke MRI with Diffusion Probabilistic Models through Large-Scale Pre-training and Target-Specific Fine-Tuning
Yamin Arefeen, Sidharth Kumar, Steven Warach et al. (+2 more)
Purpose: To develop a data-efficient strategy for accelerated MRI reconstruction with
Diffusion Probabilistic Generative Models (DPMs) that enables faster scan times in clinical stroke MRI when only limited fully-sampled data samples are available. Methods: Our simple training strategy, inspired by the foundation model paradigm, first trains a DPM on a large, diverse collection of publicly available
brain MRI data in fastMRI and then fine-tunes on a small
dataset from the target application using carefully selected learning rates and fine-tuning durations. The approach is evaluated on controlled fastMRI experiments and on clinical stroke MRI data with a blinded clinical reader study. Results: DPMs pre-trained on approximately 4000 subjects with non-FLAIR contrasts and fine-tuned on FLAIR data from only 20 target subjects achieve reconstruction performance comparable to models trained with substantially more target-domain FLAIR data across multiple acceleration factors. Experiments reveal that moderate fine-tuning with a reduced learning rate yields improved performance, while insufficient or excessive fine-tuning degrades reconstruction quality. When applied to clinical stroke MRI, a blinded reader study involving two neuroradiologists indicates that images reconstructed using the proposed approach from $2 \times$ accelerated data are non-inferior to standard-of-care in terms of image quality and structural delineation. Conclusion: Large-scale pre-training combined with targeted fine-tuning enables DPM-based MRI reconstruction in data-constrained, accelerated clinical stroke MRI. The proposed approach substantially reduces the need for large application-specific
datasets while maintaining clinically acceptable image quality, supporting the use of foundation-inspired
diffusion models for accelerated MRI in targeted applications.
Read the full abstract ▾
All authors Yamin Arefeen, Sidharth Kumar, Steven Warach, Hamidreza Saber, Jonathan Tamir