Atomic Physics
Observation of the liquid-gas transition in trapped ions
Eliana Ruth Wallach, Yohay Halfon, Yosef Alkoby et al. (+4 more)
Precision metrology,
quantum information, and
quantum-controlled chemistry studies all have many implementations in trapped ion systems that require a precise understanding of the motional dynamics of ions. Between the well-studied Coulomb-
crystal and gaseous regimes lies the intermediate
liquid-like regime whose properties and boundaries have largely eluded experimental investigation. Here, we track the entire
liquid-to-gas transition process by leveraging direct velocity measurements using our newly developed ion-trap with integrated velocity map imaging. We demonstrate that the colder the ensemble, the more viscous the ion motion becomes until radial localization emerges, which marks the onset of the
liquid regime at a temperature warmer than commonly assigned. At even hotter temperatures, we observe an abrupt change in the heating rate power-law, which indicates the maximum density threshold. The enhanced sensitivity of direct velocity measurements reveals the full transition process from a fluid with short-range order to a weakly-interacting gas.
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All authors Eliana Ruth Wallach, Yohay Halfon, Yosef Alkoby, Yair Rajmiel, Nevo Werner-Reiss, Ilan Kleinman, Yuval Shagam
Plasma Physics
Particle pinch in global tokamak edge simulations
Ben Zhu
The inward particle flux, or particle pinch, is routinely observed in magnetically confined fusion experiments, yet its mechanism is not fully understood. We study the particle pinch in the tokamak edge with the flux-driven global
turbulence model GDB. Starting from a flat density profile fueled only near the last closed flux surface, the simulation develops a strong inward particle flux that builds a centrally peaked density profile over $O(10)$ ms. The pinch coexists with the usual outward turbulent heat transport; two distinct mechanisms carry it. In the early stage, when density and temperature gradients oppose each other ($\eta_\alpha=L_n/L_{T_\alpha}<0$), drift-wave
turbulence drives the inward flux through electron thermal
diffusion. In the late stage, once the density profile has flattened, a persistent inward
equilibrium $E\times B$ flux, carried by the poloidally asymmetric density and electrostatic potential, drives the central peaking. While the Pfirsch–Schlüter neoclassical transport sets the amplitude of the up-down asymmetric density, classical theory predicts no net radial flux from this asymmetry at leading order. The observed flux flows in a separate non-ideal channel, opened by parallel resistivity, electron inertia, and electromagnetic induction in the
equilibrium electron force balance. This channel shifts the
equilibrium potential poloidally against the density by $\delta_s\simeq-0.08\pi$ and supplies the late-phase density build-up. These results show that a flux-driven global edge simulation can self-consistently produce a centrally peaked density profile without ad hoc assumptions, and bear on longstanding edge questions such as density pedestal formation.
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Chemical Physics · Cross-listed from cond-mat.mtrl-sci
Collective Excitonic Structure Governs Anomalously Weak Thermal Optical Dephasing in Conjugated Polymers
Henry J. Kantrow, Elizabeth Gutiérrez-Meza, Eric R. Bittner et al. (+2 more)
Conjugated
polymer aggregates exhibit optical decoherence in the presence of strong vibronic coupling and substantial diversity in chemical structure, solid-state organization, and excitonic character. Here, we use coherence-detected and population-detected two-dimensional electronic spectroscopies to examine the temperature dependence of the homogeneous optical linewidth across a series of semiconducting
polymers. Despite substantial differences in molecular architecture and solid-state organization, all
polymers studied exhibit remarkably weak thermal linewidth scaling over the measured temperature range. Comparison between complementary detection modalities further shows that, while this weak temperature dependence is obust, the absolute homogeneous linewidth depends on the measured observable. This behavior reflects the different ways in which coherence- and population-detected measurements project population relaxation and pure dephasing onto the spectroscopic response. These results establish the weak thermal scaling of optical decoherence across a diverse series of conjugated
polymers and show that its experimental manifestation must be interpreted in the context of the detection observable.
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All authors Henry J. Kantrow, Elizabeth Gutiérrez-Meza, Eric R. Bittner, Hao Li, Carlos Silva-Acuña
Computational Physics
A HIP-Compatible Accelerator Backend for Fourier-Bessel Particle-in-Cell Simulations on CPU/DCU Heterogeneous Clusters
Jingliang Fan, Ruiqing He, Yang Wan et al. (+3 more)
FBPIC (
Fourier-Bessel particle-in-
cell) is a high-performance simulation code for relativistic
plasma and accelerator physics. Its original accelerator backend relies on Numba CUDA, which limits its direct deployment on accelerators using the HIP (Heterogeneous-Compute Interface for Portability) programming environment, such as DCU (Deep Computing Unit) accelerators. In this work, we develop an accelerator backend compatible with HIP that enables FBPIC to run efficiently on DCU platforms while preserving its Python user interface and high level simulation workflow. For the evaluated LWFA (
laser-wakefield acceleration) workloads, the proposed backend achieves 1.32-1.54x speedups over the original FBPIC implementation on an NVIDIA V100 GPU and enables efficient execution on the DCU platform. We also summarize the key lessons learned from porting FBPIC to the DCU platform. Multi-DCU experiments achieve a 1.88x strong-scaling speedup on four accelerators and a 2.72x increase in aggregate throughput at approximately 68% weak-scaling efficiency, with communication analysis identifying inter-node communication and synchronization as the main scalability limitations. Beyond FBPIC, the proposed approach provides a practical reference for porting and optimizing other scientific computing applications developed with Python on heterogeneous accelerator platforms.
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All authors Jingliang Fan, Ruiqing He, Yang Wan, Jiandong Shang, Hengliang Guo, Qiang Chen
General Physics
Algebraic solutions for propagation of elastic SH-waves through an isotropic inhomogeneous geometry
Saber Zarrinkamar
The algebraic structure of the equation governing the propagation of an elastic SHwave through an isotropic inhomogeneous layer surrounded by two homogeneous half-spaces is revisited. It is shown that the problem under a quartic variation has a hidden sl(2)
symmetry based on which quasi-exact solutions are available via a completely analytical approach. This is of particular interest as the approach proposed for the corresponding tri-confluent Heun equation can be generalized to some other classes of geometries as well and the complicated considerations in case of Heun equations are absent.
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Chemical Physics
Out-of-Distribution Inverse Design of Elastic Networks with Differentiable Graph Neural Network Molecular Dynamics
Sergey A. Shteingolts, Salman N. Salman, Ron Levie et al. (+1 more)
Machine-learning-based inverse design can accelerate the discovery of materials with targeted properties, but conventional structure–property models often require large training
datasets and generalize poorly beyond their training distribution. Here, we present a differentiable inverse design framework based on a graph neural network molecular dynamics simulator. By combining a short dynamical initialization with physics-based refinement during simulation, the framework enables optimization well beyond the conditions represented in the training data. Using disordered elastic networks, we show that a simulator trained only on non-auxetic systems with Poisson's ratios between 0.1 and 0.4 can design strongly auxetic networks with values as low as -0.3. The framework also produces stress–strain responses outside the range observed during training, creates localized mechanical defects absent from the training data, and generalizes across system size, enabling optimization of networks tested up to 5000 nodes despite being trained only on networks with fewer than 200 nodes.
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All authors Sergey A. Shteingolts, Salman N. Salman, Ron Levie, Dan Mendels
Optics
A tunable chiral light-matter interface with on-chip spin control
Shikai Liu, Joan Alba, Bálint Sárközi et al. (+5 more)
The ability to engineer
chiral light-matter interactions is a valuable resource for realizing
quantum networks and non-reciprocal
quantum optics. Here, we demonstrate
chiral coupling between light and a negatively charged
exciton state, i.e., a four-level system, embedded in a standard photonic-
crystal waveguide. By controlling the orientation and strength of an external
magnetic field, we tune the polarization of the individual optical transition dipoles relative to the fixed elliptically polarized waveguide mode. In a two-sided waveguide, an optimized oblique
magnetic field allows a selected transition to decay exclusively into a single propagation direction, enabling near-unity directional emission ($0.99^{+0.01}_{-0.02}$), despite the waveguide exhibiting imperfect polarization for
chiral coupling. We further observe two tunable
chiral branching ratios, the directional analogue of optical cyclicity, for two $\Lambda$-systems, with one reaching $134_{-77}^{+\infty}$. The
magnetic-field-dependent spectroscopy also allows reconstruction of the local guided-mode polarization at the emitter via the Stokes parameters relative to the emitter's dipole moments. Finally, we demonstrate that this local chirality enables coherent control of an electron
spin via an optical Raman process mediated by waveguide driving. Building on the simultaneous realization of a large branching ratio, directionality and
spin control achieved at the same oblique
magnetic-field angle, we propose a protocol with high tolerance to
photon loss for generating high-fidelity remote
spin-
spin entanglement. Our
magnetic control opens a reconfigurable and generic route for enhancing on-chip
chiral spin-
photon coupling in standard nanophotonic interfaces without the need to carefully engineer the polarization of the waveguide.
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All authors Shikai Liu, Joan Alba, Bálint Sárközi, Nikolai Bart, Arne Ludwig, Ming Lai Chan, Peter Lodahl, Anders S. Sørensen
Atomic Physics
Roadmap on Quantum Sensors for Vacuum Metrology
D.S. Barker, J.L. Booth, S.P. Eckel et al. (+7 more)
We describe how
laser-cooled and trapped alkali-metal atoms have been used as pressure sensors in the high- and ultra-high-
vacuum regimes operating with relative uncertainties of just over a percent at pressures from a few nPa and up to a few tens of $\mu$Pa. These sensors can serve as primary standards of pressure as the determination of pressure requires only knowledge of collision cross sections between atoms and molecules, eliminating the need for calibration with other devices. The collision cross sections can be measured independently or computed with rigorous
quantum methods at percent relative accuracies. We argue that this technology has advanced sufficiently to provide an alternative to the existing, expensive pressure standard in the ultra-high
vacuum regime, the orifice flow standard. Experiments with trapped atoms can be used to calibrate cheaper pressure sensors (such as devices based on ionization gauges). However, the technology has not yet matured enough to be of use in other research fields because of the complexity and cost of the experiments. We propose a roadmap for this new pressure standard for
vacuum metrology.
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All authors D.S. Barker, J.L. Booth, S.P. Eckel, J. Grosse, K. Jousten, J. Kłos, R.V. Krems, K.W. Madison, T. Rubin, E. Tiesinga
Optics
Shortcuts to adiabaticity for rapid soliton compression in nonlocal media
Yingjia Li, Qian Kong, Xihua Yang et al. (+1 more)
We investigate shortcut-to-adiabaticity protocols for the rapid compression of optical
solitons in nonlocal media. Using a variational approximation, we derive an effective Ermakov-like equation for the
soliton width and employ inverse engineering to design propagation-dependent control parameters. Three control strategies are compared, based respectively on modulation of the characteristic nonlocal length, the Kerr nonlinearity, and the external
parabolic confinement. We show that all three protocols enable high-fidelity compression over strongly reduced propagation distances. By comparing control smoothness and final fidelity, we find that the relative performance of the protocols in the very short-distance regime depends on the chosen criterion, revealing a trade-off between implementation smoothness and target-profile accuracy. These results establish a practical and general route to fast
soliton manipulation in nonlocal media.
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All authors Yingjia Li, Qian Kong, Xihua Yang, Xi Chen
Physics and Society
Blind directions of physical learning networks: where to measure and what to measure
Quoc-Bao Nguyen and Thai-Son Vu
A physical learning network is read at a few accessible nodes. Every task and learning rule that uses only the steady voltages and currents there, at a fixed operating point, acts through the boundary response map. Changes in the kernel of its Jacobian are blind to first order. A walk along one fiber ran to a 600-step cap, one edge then at 15.2 times its start. A decomposition
theorem splits the response Jacobian over the hidden components. The blind dimension adds over components whose surviving slots are disjoint. A boundary-to-boundary edge adds one parameter and deletes one slot. Exposing a hidden node changes only its component. For one hidden node the contribution counts the bipartite components of the non-adjacency graph of its neighbors. For a pocket of h hidden nodes a factor-analysis bound caps what outside electrodes can expose. It is attained when every pocket node meets every neighbor and no edge joins two of those neighbors, so past a threshold further electrodes outside such a pocket expose nothing. An electrode inside such a pocket, when its hidden nodes form a clique, is worth h-1 directions where one outside is worth none. Read as vector displacements rather than potentials, the same nodes left no deficit beyond counting in all 90 spring networks tested, each a pocket fully joined to five or more accessible nodes, and nothing blind in 88. What limits the reading is the quantity measured as much as the number of contacts. Maximum-weight spanning forests give a proved upper bound on the blind dimension. The matching equality is proved for one hidden node and conjectured beyond. It holds in all 5,343 components whose maximum could be attained and certified, and the forest count matched the certified blind dimension in 1,448 of 1,500 held-out networks, where the maximum must be searched. A self-learning
circuit shows the split on hardware.
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Atomic Physics
Floquet-sideband-enhanced shortwave electrometry with Rydberg atoms
Jiaqi Yuan, Yunlong Xue, Yongjie Cheng et al. (+7 more)
Rydberg atomic electric-field sensors, under the framework of optical excitation and readout, can overcome the size-to-wavelength constraint imposed by the Chu limit. However, their sensitivity for decametric-wavelength shortwave electric fields is substantially lower than that for microwave ones, stemming from the off-resonant nature of low-frequency signals with Rydberg transitions. Here, we demonstrate a high-sensitivity heterodyne shortwave sensor based on microwave-dressed Rydberg atoms, leveraging precisely modulated Floquet sidebands. Around local- and microwave-field-engineered Floquet sidebands, the steep response gradient, arising from the enhanced atom-shortwave interaction through additionally created coherent channels, induces pronounced amplification of the heterodyne intermediate-frequency signal. As a result, compared to the same atomic heterodyne setup without microwave modulation, such Floquet-sideband-enhanced shortwave measurement boosts the sensitivity by four orders of magnitude, yielding a sensitivity of -122.7 dBm/Hz for shortwave at 30 MHz. This work offers a potential route to high-sensitive portable shortwave receivers in
radio astronomy, radar and long-distance communications.
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All authors Jiaqi Yuan, Yunlong Xue, Yongjie Cheng, Ruidong He, Jiteng Sheng, Yanpeng Zhang, Zhengyang Bai, Yu-Qiang Ma, Min Xiao, Zhaoyang Zhang
Plasma Physics
Magnetic island structures in relativistic laser-driven plasma channels
Dongchi Cai, Zheng Gong, Guanqi Qiu et al. (+3 more)
We develop a theoretical model for self-generated
magnetic islands in relativistic
laser-driven channels in near-critical-density
plasmas. The islands arise from the nonlinear superposition of the quasi-static
magnetic fields generated by the longitudinal channel current $j_x$ and the
laser-front driven transverse current $j_y$. By deriving the critical conditions among
laser depletion, transversely symmetric channel formation, and
magnetic-island formation, we identify the
laser-
plasma parameter window in which the
magnetic island structures can exist. Within this window, the balance between the
laser ponderomotive force and the charge-separation force, expressed through an effec tive electron density $n_\mathrm{eff}$, determines the transverse island width $H$, whereas the mismatch between the
laser group and phase velocities determines the longitudinal period $L$. Large-scale particle-in-
cell simulations over a broad range of
laser intensities and
plasma densities validate the resulting scaling laws. The model turns the island geometry from a qualitative feature of the channel field into a predictable quantity, providing a basis for tailoring electron transport, particle acceleration, high-energy radiation, and novel fusion ignition schemes in relativistic
laser-
plasma interactions.
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All authors Dongchi Cai, Zheng Gong, Guanqi Qiu, Deji Liu, Yinren Shou, Xueqing Yan
Classical Physics
Induced electromotive force of a thin metal rod in the alternating electromagnetic field of Helmholtz coil: experimental results and theoretical analysis
Yilin Shao, Minghan Gao, Baiqing Li et al. (+2 more)
We apply a thin metal rod (copper rod) as a probe in the alternating
magnetic field generated by a Helmholtz coil, and measure the variation of the induced electromotive force (EMF) on the metal rod at different radial positions of Helmholtz coil. Experimental results show that the induced EMF is zero when the center of the metal rod passes through the center of the cylindrical
magnetic field inside the Helmholtz coil. When the metal rod is displaced from the center of field to different radial positions, the induced EMF gradually increases from zero, reaches a maximum at a certain position, and then decreases monotonically as the radial distance continues to increase. At the position where the induced EMF reaches its maximum, the metal rod intersects the radial cross-section of the internal
magnetic field of the Helmholtz coil at two points, with a small central portion of the rod located inside the Helmholtz coil and the two end portions outside the coil. To explain the experimental phenomena, we construct four simplified models of the
magnetic field distribution based on the actual field distribution of the Helmholtz coil to quantitatively investigate the radial variation of the induced EMF along the metal rod. Our theoretical results show that the four models yield similar results and can all qualitatively explain the experimental data curves, particularly reproducing well the variation trend of the induced EMF and the position of the extremum point. The result of piecewise function fitting model is quantitatively in good agreement with the experimental data. This work is also very much helpful and instructive for undergraduate-level students.
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All authors Yilin Shao, Minghan Gao, Baiqing Li, Xiaoguang Li, Chengfu Mu
Optics
Recovering topological information of light by topological learning
Benquan Wang, Trishita Das, Yuhan Peng et al. (+8 more)
The
evolution of modern-day communication networks towards optical solutions with enhanced capacity and robustness is driving interest in topological light waves, exploiting their stability against perturbations through a topological invariant, e.g., the skyrmion number. However, detecting the underlying
topology remains a computationally intense process even under ideal conditions, becoming intractable after passing through strongly disordered channels, where the degradation into unrecognisable speckle appears to destroy the
topology. Here, we propose and demonstrate a
topology-enhanced artificial intelligence (AI) approach to recover and classify such apparently lost topological information by computationally leveraging topological invariants in the data across many length scales. By aligning the topological classification of information with the
topology of light, our
topology-enhanced learning protocol, termed TOPO$^{2}$, achieves highly efficient recognition of the topological states of light, even from speckle, without the need for any prior learning. Our approach outperforms
benchmark tests against standard computational
algorithms and has the benefit of requiring just a single intensity pattern as the input, facilitating single-shot operation. To demonstrate this, we leverage the skyrmion number as a robust data carrier of images through a disordered channel, using TOPO$^{2}$ to accurately reconstruct the transmitted images. This work synergises topological photonics and topological AI for unravelling hidden topological signatures in light, opening a pathway towards robust communications even in extreme disordered environments.
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All authors Benquan Wang, Trishita Das, Yuhan Peng, Tatjana Kleine, Shanshan Chang, Jinhui Chen, Nilo Mata-Cervera, Chunyu Li, Kelin Xia, Andrew Forbes, Yijie Shen
Accelerator Physics
Incoherent scattering of highly ultrarelativistic channeled particles on electrons
Victor V. Tikhomirov
This article systematically examines the effects that must be taken into account when modeling the dechanneling of highly ultrarelativistic charged particles caused by incoherent scattering by electrons of
crystal atoms. Changes in the particle electromagnetic field that occur in condensed matter at highly ultrarelativistic energies are taken into account. The excitation of both collectivized electrons and inner-shell electrons of atoms is considered, taking into account thermal vibrations and the inhomogeneous periodic distribution of atoms in
crystals. Differences in the calculations of stopping power and mean square scattering angle by electron of channeled particles are described. The need to separate both of them into diffuse processes, accompanied by the transmission of a transverse momentum which does not exceed the transverse momentum of the channeled particles, and instantaneous dechanneling processes with a greater transmitted momentum, the variation range of which reaches several orders of magnitude, is substantiated. The main result of the present work is expressions for the mean square projected scattering angles per unit length in planes parallel and perpendicular to the atomic plane, which also allow for the introduction of effective minimum momenta for incoherent scattering. Expressions of both types take into consideration completely the nonlocal effects of momentum transfer from
crystal electrons to particles moving along classical trajectories, and allow for the formulation of simple methods for modeling the incoherent scattering of ultrarelativistic positively charged particles.
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Computational Physics
A Sparsity-Promoting Electromagnetic Inversion Method Regularized by $\ell_1 / \ell_2$-Norm of the Model Gradient
Lingqi Gao and Hakan Bagci
A nonlinear EM inversion method regularized by $\ell_1 / \ell_2$-norm of the model gradient is proposed. The $\ell_1 / \ell_2$-norm, defined as the ratio of $\ell_1$-norm to $\ell_2$-norm, exhibits a scale-invariant property that enables it to more accurately characterize sparsity in the solution compared with the conventional $\ell_1$-norm. To address the nonconvexity and nonsmoothness introduced by the quotient structure of $\ell_1 / \ell_2$-norm, the inversion problem is reformulated and solved using the alternating direction method of multipliers, resulting in an efficient optimization
algorithm comprising five sub-steps. The Gauss–Newton method is incorporated into the first sub-step to linearize the nonlinear inversion. The proposed method is validated by a series of numerical examples using both synthetic and experimental
datasets, and is compared against standard regularization methods such as Tikhonov and total variation. The results demonstrate that the proposed method yields superior reconstructions of permittivity profiles, particularly in preserving sharp edges and suppressing artifacts, without incurring additional computational cost. Furthermore, the method exhibits strong robustness to measurement noise and reduced sensitivity to the choice of the regularization weight.
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Biological Physics · Cross-listed from cond-mat.quant-gas
Superfluidity in active quantum flocks
Byjesh N. Radhakrishnan, Reyhaneh Khasseh, Thomas Schmidt et al. (+1 more)
Active
quantum matter has very recently emerged at the intersection between bio- and
quantum many-body physics, combining the self-organization of living systems with the coherence of the
quantum world. Active
quantum systems have been shown to exhibit flocking - a collective phenomenon with no precedent in
equilibrium quantum physics. In this work we uncover an unexpected layer of
quantum order in active
quantum flocks: they can become superfluid. We show that, in addition to the
symmetry breaking associated with their directed motion, these flocks can also break an additional U(1)
symmetry, giving rise to off-diagonal long-range order. For a microscopic model of active hard-core
bosons governed by Lindblad dynamics, we derive an effective long-wavelength description of the single-particle density
matrix and demonstrate that the flocking phase develops an instability toward off-diagonal long-range order characteristic of superfluid behavior. Our findings reveal active
quantum matter as a promising research direction for discovering exotic nonequilibrium phases of
quantum matter.
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All authors Byjesh N. Radhakrishnan, Reyhaneh Khasseh, Thomas Schmidt, Markus Heyl
Optics · Cross-listed from astro-ph.IM
Mechanisms of Electrostatic Charge Formation and Retention in Lunar Regolith
Minhyeok Kim, Hyun Jung Kim, Sang H. Choi et al. (+1 more)
As the Artemis program advances toward the lunar south pole and permanently shadowed regions (PSRs), understanding lunar charging is increasingly important for protecting astronauts, robotic systems, instruments, and infrastructure. Persistent darkness, cryogenic temperatures, low regolith conductivity, and long charge-relaxation times may allow energetic-particle-induced charge to accumulate beneath the surface. This Technical Memorandum addresses a key unresolved question: how is electrostatic charge generated, separated, retained, and accumulated within lunar regolith? Existing models predict that
solar energetic particles and
galactic cosmic rays may produce subsurface electric fields approaching dielectric breakdown thresholds, but the microscopic connection between incident particles and macroscopic volumetric charge sources remains unclear. Energy deposition alone does not determine retained charge. Incident particles and their secondary particles may stop, implant, backscatter, transmit, recombine, become trapped, or escape. This memorandum therefore defines the required microscopic input as the average signed retained-charge distribution per unit depth and incident particle, resolved by particle species and energy. Combined with incident flux and energy spectra, this response provides a depth-dependent volumetric charge-source rate that can be coupled with charge continuity, conduction, dielectric relaxation, and Poisson's equation. Key uncertainties include the effects of mineralogy, grain and pore geometry, temperature, and pre-existing potential on charge retention. Particle-resolved modeling and cryogenic high-
vacuum irradiation experiments are needed to constrain these processes and assess subsurface electric fields, dielectric breakdown,
dust transport, contamination, and charge-mitigation requirements for sustained lunar polar exploration.
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All authors Minhyeok Kim, Hyun Jung Kim, Sang H. Choi, Ashley Daeun Jung
Optics · Cross-listed from quant-ph
Quantum Optics of harmonic generation in the strongly driven Jaynes-Cummings-type system
M Suman, Sili Yi, Maria Chekhova et al. (+1 more)
We adapt the Jaynes-Cummings model to study the interface of cavity
quantum electrodynamics with strong field and attosecond physics. We show how multi-
photon resonances in the Jaynes- Cummings system driven by a strong low-frequency classical light field lead to the generation of highly non-classical,
quantum-correlated harmonics of the classical driver. Our treatment assumes no approximations, apart from the typical Jaynes-Cummings model assumption of only a few discrete
quantum modes of light. The paper is dedicated to Joseph Henry Eberly, whose remarkable research has left indelible mark on both strong field physics and
quantum optics.
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All authors M Suman, Sili Yi, Maria Chekhova, Misha Ivanov
Optics · Cross-listed from quant-ph
Generation of entanglement statistics with a large-scale integrated photonic-electronic circuit
Volkan Gurses and Ali Hajimiri
Continuous-variable
quantum processors scale with the modes they can transform, and each transformation adds loss. We demonstrate optoelectronic
quantum information processing, moving the mixing into
radio-frequency electronics after homodyne detection. Squeezed
vacuum falls on a large-scale integrated photonic-electronic
circuit, a 32-channel coherent receiver array whose
radio-frequency network mixes the analog photocurrents. A local-oscillator ramp reconstructs the two-mode covariance at the aperture, which is physical, and its partial transpose has smallest
symplectic eigenvalue 0.99270, three standard deviations below the separability bound. Mode transformation becomes a
circuit function whose scale follows integrated electronics. With electro-optic transducers in place of the photodiodes, the same receiver would transfer optical modes into superconducting
circuits and back, toward a photonic-electronic
quantum computer spanning the optical and microwave bands.
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Fluid Dynamics
Unification of The Navier-Stokes Equation for Fluid Mechanics and Aeroacoustics
Tapan K. Sengupta
The Navier-Stokes equation for a compressible Newtonian fluid is reassessed, in view of recent investigation results on the foundations of aeroacoustics. In the process, the role and necessity of the so-called Stokes' hypothesis is reconsidered, which in its current practice omits the bulk viscosity. In contrast, the relevance of a new generalized kinematic viscosity is proposed, along with a new methodology that will enable estimation of second coefficient of viscosity completely obviating the necessity of making the Stokes' hypothesis. This opens up the vista of a new formulation for the Navier-Stokes equation applicable for both the subjects of fluid mechanics and aeroacoustics in a unified approach.
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Optics
Energy-scalable single-burst attosecond emission at kiloelectronvolt photon energies
Kaito Nishimiya and Eiji J. Takahashi
Attosecond soft-X-ray pulses at kiloelectronvolt
photon energies would provide direct access to the L-edges of transition metals, enabling element-specific studies of charge,
spin, and orbital dynamics on their intrinsic timescales. However, attosecond emission in this spectral region has remained elusive because the only phase-matched keV high-harmonic source demonstrated to date employed multicycle driving pulses without carrier-envelope-phase (CEP) control. A long-standing gap has therefore persisted between keV
photon energies and CEP-controlled attosecond emission. Here, we bridge this gap using a CEP-stabilized mid-infrared
laser system with pulse durations tunable to the sub-cycle regime. Through phase-matched highharmonic generation in low-pressure neutral helium under meter-scale loose-focusing conditions, we generate coherent soft-X-ray continua reaching 1.2 keV. Crucially, we observe CEP-dependent spectral modulation that reaches into the transition-metal L-edge region, providing experimental evidence consistent with the generation of isolated attosecond pulses. To demonstrate the capabilities of our source, we perform broadband soft-X-ray absorption spectroscopy spanning the Ti, Fe, Co, and Ni L-edges, as well as the O K-edge, and resolve near-edge fine structures. By combining meter-scale loose focusing with low-pressure phase matching, our approach addresses key energy-scaling limitations of previous keV high-harmonic sources and establishes a phase-matched, CEP-controlled keV soft-X-ray platform for attosecond spectroscopy of
magnetic,
quantum, and strongly correlated materials.
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Computational Physics · Cross-listed from math.NA
High-Order Structure-Preserving SBP Finite Difference Methods for the Vlasov-Maxwell System on Matrix-Free GPUs
Robin Dymér, Ken Mattsson and Murtazo Nazarov
In this paper, we present a high-order, stable summation-by-parts (SBP) finite difference method for solving the Vlasov-Maxwell system in a 2D2V phase space. Central SBP operators for the advection terms are not stable when the solution becomes non-smooth and fine-scale filamentary structures develop, as is typical in high-dimensional Vlasov-Maxwell simulations. To address this issue, the method is stabilized using high-order upwind SBP operators. High-order explicit Runge-Kutta methods are employed for time integration. We prove that the fully discrete scheme exactly conserves mass and preserves momentum up to truncation error. Furthermore, we present a
matrix-free implementation of the method on modern GPU architectures. A range of challenging
benchmark problems is solved to demonstrate the accuracy, robustness, and performance of the proposed scheme.
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Chemical Physics
Tensor-based Approximation of Molecular Kinetics: Generator Learning, Reaction Coordinates and Incremental Updating
Minakshi Verma, Peter Benner and Feliks Nüske
We present an approach to analyze long-timescale kinetics of molecular dynamics simulations - meta-stable states and transition timescales - by a tensor-based approximation of the infinitesimal generator. We start from the variational approximation of low-lying generator
eigenvalues, and discretize the associated
eigenvalue problem using a tensor-product basis. We derive analytical expressions for the resulting tensor operators in tensor train (TT) format, and provide efficient
algorithms to solve the corresponding linear problems. We also treat the case of a state-dependent
diffusion field, which is relevant when working in reaction coordinates. We show how the number of reaction coordinates can be gradually increased without having to solve the variational problem from scratch. Using MD simulations of fast-folding
proteins and TICA coordinates as reaction coordinates, we demonstrate the effectiveness of the proposed method at identifying long-timescale transitions and meta-stable states.
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Applied Physics · Cross-listed from cond-mat.mtrl-sci
$\beta-(Al_{0.19} Ga_{0.81})_2 O_3/Ga_2 O_3$ Modulation-Doped Field-Effect Transistors with $>$ 6 kV Breakdown
Julian Gervassi Saga, Joshua T Buontempo, Nabasindhu Das et al. (+3 more)
$\beta-(Al_{0.19} Ga_{0.81})_2 O_3/Ga_2 O_3$ modulation-doped field-effect transistors (MODFETs) incorporating a high-quality Al2O3 gate dielectric and SiNx passivation are demonstrated for high-voltage operation. The devices exhibited a maximum drain current of 54 mA/mm, an on-resistance of 149 Ohm.mm, a minimum subthreshold slope of 94 mV/dec, and an ION/IOFF ratio exceeding $10^8$. Three-terminal breakdown measurements performed in Flourinert demonstrated a breakdown voltage that increased with gate-drain spacing, reaching 6.6 kV for a device with LGD = 28 microns. The corresponding average lateral electric field approached 2.4 MV/cm, while a power figure of merit of 222 MW/cm2 was achieved. To the best of the authors knowledge, the demonstrated breakdown voltage represents the highest reported value for a $\beta-(Al_x Ga_{1-x})_2 O_3/Ga_2 O_3$ MODFET and highlights the potential of modulation-doped $\beta$-Ga2O3
heterostructures for next-generation multi-kV power devices.
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All authors Julian Gervassi Saga, Joshua T Buontempo, Nabasindhu Das, Advait Gilankar, Hari P Nair, Nidhin Kurian Kalarickal
Accelerator Physics
Preliminary design of continuous wave Low-Level RF systems for S3FEL
Z. Y. Zhang, J. F. Zhu, H. L. Ding et al. (+4 more)
In the Shenzhen Superconducting Soft X-ray Free Electron
Laser (S3FEL), Continuous Wave (CW) Low-Level
Radio Frequency (LLRF) systems perform critical functions including adjusting the power coupling of accelerator cavities, regulating the amplitude and phase of the RF field, and maintaining the resonance frequency and phase of the cavities. These functions are essential to ensure the electron beam operates at the accelerating phase. Within S3FEL, each superconducting cavity is driven by a solid-state amplifier (SSA), with each SSA paired with a dedicated LLRF system. Based on the distinct acceleration cavities employed, the CW LLRF systems for S3FEL are categorized into four types: 1. Primary accelerator LLRF systems (superconducting, 1.3 GHz; quantity: 168), 2. Harmonic cavity LLRF systems (superconducting, 3.9 GHz; quantity: 16), 3. VHF electron gun LLRF systems (room temperature, 216 MHz; quantity: 4), 4. Buncher LLRF systems (room temperature, 1.3 GHz; quantity: 2). These four LLRF system categories exhibit differing requirements for RF field and acceleration cavity control. This report presents the preliminary design schemes for these four types of CW LLRF systems.
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All authors Z. Y. Zhang, J. F. Zhu, H. L. Ding, J. W. Han, W. Li, J. Y. Yang, W. Q. Zhang
Optics · Cross-listed from quant-ph
Telecom-Integrated Photonic Memory Operating Near the Mechanical Ground State
Jindao Tang, Bo Jing, Liping Zeng et al. (+11 more)
Scalable
quantum networks require
quantum memories that are chip-integrated, telecom-band compatible, and capable of flexible
retrieval. Nanofabricated mechanical resonators meet these criteria. They offer independent tunability of optical and mechanical modes, long-lived
phonon states, and design flexibility beyond atomic systems, making them strong candidates for practical integrated
quantum memory. Here, we demonstrate an on-chip, absorptive optomechanical
memory for telecom-band
photons, based on optomechanically induced transparency (OMIT) and operating near the mechanical ground state. The device stores telecom-band
photons, demonstrating compatibility with external
photon sources at the few-
photon level, while enabling on-demand
retrieval. By placing the device in a dilution refrigerator at 20 mK and tailoring the control field to suppress optical heating, we achieve a remarkably low
phonon occupancy of just 0.32 during the storage process. Our results lay the groundwork for scalable,
phonon-based
quantum memory devices and open new avenues for integrating mechanical systems into practical
quantum network architectures.
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All authors Jindao Tang, Bo Jing, Liping Zeng, Peiqin Chen, Hengrui Liang, Yifei Zhang, Xinyao Xu, Qizhi Cai, Xueying Zhang, Qiang Zhou, You Wang, Haizhi Song, Guangcan Guo, Guangwei Deng
Fluid Dynamics
Transverse transport of microswimmers in oscillatory channel flows
Raghav Ram and Ashwin Ramachandran
Motile microorganisms inhabit oscillatory flows encountered in physiological and engineering systems, yet the influence of flow unsteadiness on their shear-induced preferential concentration remains less understood. We investigate transverse transport of elongated microswimmers in oscillatory pressure-driven channel flow using complementary Langevin simulations and two- and one-dimensional Fokker-Planck models. Agreement between particle-based and continuum descriptions across governing parameters establishes the fidelity of the Fokker-Planck formulation for swimmer transport in oscillatory shear flows. Our analysis demonstrates that oscillatory forcing fundamentally modifies classical steady-flow shear-trapping. We find that increasing Womersley number $Wo$ reduces centerline depletion by confining oscillatory shear to thinner near-wall regions. In contrast, increasing frequency ratio $\beta$, of swimmer rotational
diffusion rate and flow oscillation frequency, promotes sustained orientational anisotropy, and leads to a saturating increase in centerline depletion. In the weak-swimming limit, we derive a hierarchy of coupled orientational moments, enabling analytical solutions at arbitrary temporal harmonic order. The asymptotic solutions establish a universal transfer law showing that, for a given swimmer shape, the normalized leading-order orientational response depends solely on $\beta$. Reconstruction of the orientational distribution yields closed-form expressions for the swimmer concentration profile and depletion index, $I_D$. Our asymptotic solution recovers the steady-flow weak-shear scaling of $I_D$ with flow Peclet number, $Pe_f$, of $I_D \propto Pe_f^2$, and reveals that oscillatory forcing attenuates this response by a factor $16\beta^2/(1+16\beta^2)$. These results provide a theoretical framework to predict transverse transport of microswimmers in oscillatory channel flows.
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Fluid Dynamics
Turbulence Decay Intensifies Clustering of Bubbles and Particles
Dante L. Naylor, Zhiyu Yang, Lei Yi et al. (+3 more)
Our understanding of inertial particle dynamics in
turbulence is mostly based on flows held in a statistically stationary state, a particular regime that differs from many natural flows where energy input can often be intermittent or cyclic, or may abruptly cease. Here we investigate inertial particle and bubble dynamics in freely decaying
turbulence through complementary experiments and direct numerical simulations. While particle accelerations decay monotonically in time, we find evidence that the clustering can exhibit a non-monotonic
evolution, intensifying sharply before subsequently weakening. We demonstrate that both the acceleration and clustering behaviors can be mapped onto their counterparts in stationary
turbulence using a dynamic rescaling of the evolving length and time scales of the
turbulence. Validity conditions for the dynamic rescaling, satisfied by both the experimental and numerical
datasets, are derived. The proposed mappings remain applicable across a broad range of density ratios, from light to heavy particles, and particle sizes spanning two orders of magnitude in Stokes number.
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All authors Dante L. Naylor, Zhiyu Yang, Lei Yi, Rodolfo Ostilla Monico, Enrico Calzavarini, Varghese Mathai
Atomic Physics · Cross-listed from quant-ph
Trapped Ion Quantum Networking and Telecommunications Coexisting on One Fiber
Denton Wu, Mingzhe Han, Zehao Wang et al. (+5 more)
Research into long-distance
quantum memory-based networking to date has exclusively used dark fibers. This avoids the detector background from telecommunications (telecom) traffic, but as a result excludes many fibers deployed in the field. If
memory-
photon entanglement and telecom signals coexist on one fiber, the entire classical fiber infrastructure becomes available for
quantum links. We present the first experimental demonstration of such coexistence. Ion-
photon entanglement using 1092 nm
photons emitted by a Strontium-88 ion is distributed over a deployed 2.8 km fiber loop which carries Ethernet and 5G traffic. All classical control signals required to coordinate the
quantum transmitter and receiver systems co-propagate on the same fiber. These include fiber sensing for polarization stabilization. Our results demonstrate that
memory-based
quantum networks can be realized on active classical network infrastructure.
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All authors Denton Wu, Mingzhe Han, Zehao Wang, Ana Luiza Ferrari, Mika A. Zalewski, Yuanheng Xie, Tingjun Chen, Norbert M. Linke