Showing 1–50 of 169 results for author: Zhu, C

Quasi-single-stage optimization for advanced stellarators

Authors: Guodong Yu, Yidong Xie, Hengqian Liu, Caoxiang Zhu

Abstract: Advanced stellarator design requires a balance between plasma performance and the manufacturability of three-dimensional modular coils. In conventional two-stage optimization, the coils required to realize an optimized equilibrium can be limited by engineering feasibility. Here, we develop a quasi-single-stage (QSS) framework that incorporates coil feasibility directly into plasma-boundary optimiz… ▽ More Advanced stellarator design requires a balance between plasma performance and the manufacturability of three-dimensional modular coils. In conventional two-stage optimization, the coils required to realize an optimized equilibrium can be limited by engineering feasibility. Here, we develop a quasi-single-stage (QSS) framework that incorporates coil feasibility directly into plasma-boundary optimization. QSS uses the maximum normalized normal-field error, evaluated rapidly from surface currents on a uniformly offset winding surface, as a coil-feasibility surrogate. We apply this method to optimize configurations targeting quasi-axisymmetry, quasi-helical symmetry, quasi-isodynamicity, and a combination of omnigenity with piecewise omnigenity. The QSS-optimized configurations exhibit smoother plasma boundaries and winding surfaces, lower normal-field reconstruction errors, and reduced coil complexity, while preserving favourable magnetic-symmetry and transport properties. QSS provides a practical proof-of-principle strategy for co-optimizing plasma physics and coil engineering in stellarator design. △ Less

Submitted 4 August, 2026; originally announced August 2026.

Optimized finite-$β$ tokamak-stellarator hybrid configurations achieved by planar dipole-field coils

Authors: Yihui Liang, Hengqian Liu, Guodong Yu, Zhenyu Zhou, Caoxiang Zhu, Yao Zhou

Abstract: Tokamak--stellarator hybrids seek to combine tokamak-like compactness and confinement with stellarator-like externally generated rotational transform and steady-state operation. In this work, we build on the recent tokamak--stellarator hybrid study using planar dipole-field coils (PDCs) [Yu et al., arXiv:2605.03599], in which the fixed-position, programmable coils on an axisymmetric winding surfac… ▽ More Tokamak--stellarator hybrids seek to combine tokamak-like compactness and confinement with stellarator-like externally generated rotational transform and steady-state operation. In this work, we build on the recent tokamak--stellarator hybrid study using planar dipole-field coils (PDCs) [Yu et al., arXiv:2605.03599], in which the fixed-position, programmable coils on an axisymmetric winding surface generate flexible three-dimensional shaping fields. Using single-stage free-boundary optimization of coil currents and plasma-equilibrium parameters, we construct vacuum and finite-$β$ configurations. The vacuum cases show controllable external transform and magnetic well. The finite-$β$ cases accommodate various density, temperature, and pressure profiles, producing quasi-axisymmetric (QA) equilibria with self-consistent bootstrap current, favorable Mercier stability, and reduced demand for external current drive. Re-optimization enables $β$ ramp-up and access to different field-period QA branches with moderate coil-current changes. At large rotational transform, a toroidally omnigenous (TO)-like configuration exhibits more favorable infinite-$n$ ideal-ballooning behavior than a QA reference with matched profiles, even though ballooning stability is not directly optimized for. These results demonstrate that PDCs provide a flexible platform for achieving optimized finite-$β$ hybrid configurations. △ Less

Submitted 14 July, 2026; originally announced July 2026.

Absence of poor local minima in matrix product states

Authors: Hao-Kai Zhang, Chenghong Zhu, Shuo Liu, Shi-Xin Zhang, Tao Xiang

Abstract: Quantum circuits suffer from severe trainability issues: even shallow circuits are swamped with poor local minima. Yet matrix product states (MPS), which can be prepared by sequential circuits, are remarkably trainable in practice -- as demonstrated by decades of successful density matrix renormalization group calculations. In this work, we resolve this apparent paradox by proving that the energy… ▽ More Quantum circuits suffer from severe trainability issues: even shallow circuits are swamped with poor local minima. Yet matrix product states (MPS), which can be prepared by sequential circuits, are remarkably trainable in practice -- as demonstrated by decades of successful density matrix renormalization group calculations. In this work, we resolve this apparent paradox by proving that the energy landscapes of MPS are free from poor local minima, under the same setting where brickwork circuits are not. The key insight is that the gauge freedom of MPS creates an effective local overparametrization that causes local minima to concentrate near the global minimum, analogous to overparametrized classical neural networks. We rigorously prove that the local minimum distribution is invariant under moves of the orthogonality center of MPS representations. Numerical experiments further confirm that the optimization of sequential circuits converges to near-optimal solutions even for random Hamiltonians, in stark contrast to brickwork circuits. Our findings establish a theoretical understanding of the trainability of MPS, providing a valuable guide for designing variational quantum circuits and algorithms with better trainability in the future. △ Less

Submitted 30 June, 2026; v1 submitted 8 June, 2026; originally announced June 2026.

Comments: 35 pages, 3+6 figures

Giant third-order polarization rotation via wave-mixing-induced symmetry breaking in a Rydberg-EIT medium

Authors: Lintian Luo, Yan Li, Chengjie Zhu, Runbing Li

Abstract: We investigate how wave-mixing (WM)-induced symmetry breaking leads to giant third-order polarization rotation of a weak probe field in a Rydberg electromagnetically induced transparency (EIT) medium. A far-detuned counterpropagating WM field is adiabatically eliminated and retained solely as a Raman dressing of the lower Zeeman manifold. In this reduced description, the weak static magnetic field… ▽ More We investigate how wave-mixing (WM)-induced symmetry breaking leads to giant third-order polarization rotation of a weak probe field in a Rydberg electromagnetically induced transparency (EIT) medium. A far-detuned counterpropagating WM field is adiabatically eliminated and retained solely as a Raman dressing of the lower Zeeman manifold. In this reduced description, the weak static magnetic field defines the two circular propagation channels, while the WM-induced Raman coherence breaks the symmetry between these channels, without acting as a gain channel or an independent nonlinear source. The weak-probe response is calculated using a reduced density-matrix expansion for van der Waals (vdW) correlations and self-consistent Maxwell-Bloch propagation, with the nonlinear rotation extracted by subtracting the linear propagation background. Including WM dressing increases the extracted third-order rotation from 1.06 degrees to 25.70 degrees, an enhancement of more than 24 times, for the parameters considered. The response is nonmonotonic in WM strength and can even reverse sign, revealing that the WM field controls the propagation channels through symmetry breaking rather than merely amplifying the probe. Eigenchannel diagnostics further indicate that this giant rotation requires coherent excitation of both WM-dressed propagation channels, which in turn depends on three factors: Raman-induced asymmetry, the EIT-supported Rydberg pathway, and vdW nonlocality. These results demonstrate a symmetry-breaking-controlled mechanism for Rydberg magneto-optics, with applications to weak-light polarimetry and all-optical polarization control. △ Less

Submitted 20 July, 2026; v1 submitted 31 May, 2026; originally announced June 2026.

Comments: 21 pages, 5 figures

A programmable stellarator-tokamak hybrid for million-scale magnetic-configuration discovery

Authors: Guodong Yu, Xianyi Nie, Gwanggeun Seo, Daxing Huang, Hengqian Liu, Junhao Liu, Jaebeom Cho, Hyun-Su Kim, Jinlin Xie, Ge Zhuang, Fazhu Ding, Jong-Kyu Park, Caoxiang Zhu

Abstract: Tokamaks and stellarators are the leading magnetic-confinement concepts for fusion, but they rely on complementary design principles. Tokamaks use simple axisymmetric coils and plasma current, whereas stellarators use externally generated three-dimensional fields for steady-state operation. Here, we propose a programmable stellarator--tokamak hybrid that uses a fixed set of simple planar coils to… ▽ More Tokamaks and stellarators are the leading magnetic-confinement concepts for fusion, but they rely on complementary design principles. Tokamaks use simple axisymmetric coils and plasma current, whereas stellarators use externally generated three-dimensional fields for steady-state operation. Here, we propose a programmable stellarator--tokamak hybrid that uses a fixed set of simple planar coils to access a broad magnetic-configuration space. The device adds 288 dipole-field coils to a tokamak-like coil set, with only six independent coil geometries required by symmetry. By programming coil currents, the same hardware generates more than 1.66 million optimized stellarator configurations spanning quasi-axisymmetry, quasi-helical symmetry, and quasi-isodynamicity, as well as tokamak-relevant three-dimensional perturbations. Representative configurations exhibit nested magnetic surfaces, low neoclassical transport, and favorable energetic-particle confinement. This approach enables rapid magnetic-configuration discovery without hardware redesign. △ Less

Submitted 5 May, 2026; v1 submitted 5 May, 2026; originally announced May 2026.

Reconfigurable ultrafast perovskite polariton logic gates via nonlinear dynamics

Authors: Yuyang Zhang, Zhuoya Zhu, Xin Zeng, Shuai Zhang, Xinyi Deng, Tian Lan, Changhai Zhu, Kwok Kwan Tang, Qinglin Jia, Yuexing Xia, Yiyang Gong, Wenna Du, Feng Li, Rui Su, Xuekai Ma, Xinfeng Liu, Qing Zhang

Abstract: Exciton-polaritons provide a great platform for developing ultrafast all-optical logic gates for quantum and optical chips. However, progress toward practical polariton logic remains limited due to incomplete logical functionality on a single device. Herein, we present a single-device perovskite polariton platform enabling reconfigurable, ultrafast logic gates with functional completeness. The dev… ▽ More Exciton-polaritons provide a great platform for developing ultrafast all-optical logic gates for quantum and optical chips. However, progress toward practical polariton logic remains limited due to incomplete logical functionality on a single device. Herein, we present a single-device perovskite polariton platform enabling reconfigurable, ultrafast logic gates with functional completeness. The device consists of an optically trapped perovskite microwire, generating well-controlled non-equilibrium polariton condensation states for multiple logic operation channels. By tailoring the power of signal and gate beams, the same device is programmed to execute three basic Boolean functions (AND,OR,and NOT) and a high-order XOR function with a high on/off ratio of 21 dB, and a fast response time 6.7 ps. The reconfigurability arises from the selective activation of different nonlinear responses of polariton condensates, including amplification, seeding state transitions, and nonlinear interaction. These results provide valuable insights for advancing exciton-polariton logic gates. △ Less

Submitted 23 April, 2026; originally announced April 2026.

Comments: 16 pages, 5 figures

Combination of quasi-isodynamic and piecewise omnigenous magnetic fields

Authors: J. L. Velasco, I. Calvo, V. Fernández-Pacheco, M. Padidar, H. Liu, E. Sánchez, G. Yu, C. Zhu

Abstract: Due to their simultaneous optimization for radial and parallel neoclassical transport, quasi-isodynamic fields have been the main choice of stellarator magnetic configuration for most fusion reactor candidates in recent years. However, achieving a high degree of quasi-isodynamicity often comes at the cost of a strong shaping of the flux surfaces of the stellarator and complex coil geometries. In t… ▽ More Due to their simultaneous optimization for radial and parallel neoclassical transport, quasi-isodynamic fields have been the main choice of stellarator magnetic configuration for most fusion reactor candidates in recent years. However, achieving a high degree of quasi-isodynamicity often comes at the cost of a strong shaping of the flux surfaces of the stellarator and complex coil geometries. In this work, the concepts of quasi-isodynamicity and piecewise omnigenity are combined to form QI-pwO fields. These fields are quasi-isodynamic in the low-field region of the magnetic surface, whereas they significantly depart from quasi-isodynamicity in the high-field region without sacrificing the neoclassical transport properties of quasi-isodynamic fields. This departure could make it easier to integrate the optimization of neoclassical transport with other physical and technological aspects of a stellarator reactor. △ Less

Submitted 12 March, 2026; originally announced March 2026.

Optimization of stellarator configurations combining omnigenity and piecewise omnigenity

Authors: Hengqian Liu, Guodong Yu, José Luis Velasco, Caoxiang Zhu

Abstract: We present a method for optimizing stellarator configurations that combine omnigenity and piecewise omnigenity (pwO). Within the \texttt{OOPS} optimization framework [Liu \textit{et al.}, arXiv:2502.09350 (2025)], we introduce a mapping technique that can ``squeeze'' general omnigenous fields to approximate pwO in the high-field side. Using this approach, we obtain a range of optimized configurati… ▽ More We present a method for optimizing stellarator configurations that combine omnigenity and piecewise omnigenity (pwO). Within the \texttt{OOPS} optimization framework [Liu \textit{et al.}, arXiv:2502.09350 (2025)], we introduce a mapping technique that can ``squeeze'' general omnigenous fields to approximate pwO in the high-field side. Using this approach, we obtain a range of optimized configurations that combine poloidal omnigenity (PO) and pwO, spanning different field periods and aspect ratios. We further show that these configurations are compatible with a magnetic well. The resulting configurations exhibit favorable neoclassical transport and bootstrap current properties while partially relaxing the strict constraints of omnigenity. These results suggest that such configurations are promising candidates for future stellarator reactors. △ Less

Submitted 12 March, 2026; originally announced March 2026.

Comments: 21 pages, 11 figures

A vapor-cell clock with fractional frequency reaching $10^{-16}$ level stability

Authors: Siqi Wu, Zhenqi Zhang, Xingyue Liu, Chuanshuai Zhu, Zhiyuan Wang, Zhiyu Ma, Hongli Liu, Wenhao Yuan, Xiaochi Liu, Pengfei Wang, Feng Zhao, Jan Hrabina, Jie Zhang, Zehuang Lu, Ke Deng

Abstract: Compact optical clocks with high stability are essential for next-generation frequency standard field applications, from navigation to geodesy, yet existing vapor cell clock systems have remained confined to fractional instabilities over $10^{-15}$. Here we report the breaking of this long standing barrier by demonstrating a molecular iodine optical clock that reaches an instability of… ▽ More Compact optical clocks with high stability are essential for next-generation frequency standard field applications, from navigation to geodesy, yet existing vapor cell clock systems have remained confined to fractional instabilities over $10^{-15}$. Here we report the breaking of this long standing barrier by demonstrating a molecular iodine optical clock that reaches an instability of $6.6\times 10^{-16}$ and consistently operates at the $10^{-16}$ level throughout 100 s to 2000 s, surpassing all previous vapor-cell standards by nearly an order of magnitude. This achievement is enabled by a special design architecture that integrates a monolithic, drift immune spectroscopic unit bonded to an ultra low expansion glass substrate with active temperature control of key components. The whole system only occupies 25 L. The system achieves $5\times 10^{-15}$ instability at 1 s and sustains $10^{-16}$ level performance over hours, representing the first medium-term optical stability at this level from a compact, field ready package. Our work establishes that $10^{-16}$ fractional frequency instability can be engineered into robust, portable systems through holistic stability conscious design, opening a path towards high precision time keeping beyond the laboratory environment. △ Less

Submitted 27 February, 2026; originally announced March 2026.

The UK and Ireland Geophysical Array -- Concept and Design

Authors: Andrew Curtis, Karen Lythgoe, Stephen P. Hicks, Lidong Bie, Dominik Strutz, Emma Chambers, Brian Baptie, Dave Cornwell, Juliane Huebert, Jessica Irving, Glenn Jones, Sergei Lebedev, Walid Ben Mansour, Aideliz Montiel Álvarez, Stuart Nippress, Koen Van Noten, Tim Pharaoh, Romesh Palamakumbura, Nick Rawlinson, Pablo Rodriguez Salgado, James Verdon, Chuanbin Zhu, Wen Zhou, Jelle Assink, Ian Bastow , et al. (41 additional authors not shown)

Abstract: Scientific exploration of the UK and Ireland's subsurface has made important contributions to scholarship and prosperity for people and the planet, including economic growth, sustainable use of natural resources, storage of greenhouse gases, and inspiring curiosity about the Earth beneath our feet. This article outlines a vision for an array of seismological instruments spanning the UK and Ireland… ▽ More Scientific exploration of the UK and Ireland's subsurface has made important contributions to scholarship and prosperity for people and the planet, including economic growth, sustainable use of natural resources, storage of greenhouse gases, and inspiring curiosity about the Earth beneath our feet. This article outlines a vision for an array of seismological instruments spanning the UK and Ireland, UKI Array, augmented by other types of geophysical sensors, to maximise the value offered by existing equipment pools. The mission is to research natural phenomena and structure in the deep and shallow Earth, to solve problems concerning hazards and resources, to connect scientists to schools and the broader public, and thus to inspire a new generation to learn about geophysics. The vision was created through a community driven process of engagement and participation. This paper describes the concept and design of the UKI-Array; a companion paper discusses related opportunities and potential applications. △ Less

Submitted 24 February, 2026; originally announced February 2026.

INTERFACE Force Field for Alumina with Validated Bulk Phases and a pH-Resolved Surface Model Database for Electrolyte and Organic Interfaces

Authors: Cheng Zhu, Krishan Kanhaiya, Samir Darouich, Sean P. Florez, Karnajit Sen, Patrick Keil, Nawel S. Khelfallah, Eduard Schreiner, Ratan K. Mishra, Hendrik Heinz

Abstract: Alumina and aluminum oxyhydroxides underpin chemical-engineering technologies from heterogeneous catalysis, corrosion protection, functional coatings, energy-storage devices, to biomedical components. Yet molecular models that predictively connect phase structure, pH-dependent surface chemistry, electrolyte organization, and adsorption across operating conditions remain limited. Here we introduce… ▽ More Alumina and aluminum oxyhydroxides underpin chemical-engineering technologies from heterogeneous catalysis, corrosion protection, functional coatings, energy-storage devices, to biomedical components. Yet molecular models that predictively connect phase structure, pH-dependent surface chemistry, electrolyte organization, and adsorption across operating conditions remain limited. Here we introduce a unified INTERFACE Force Field (IFF) parameterization together with a curated, ready-to-use pH-resolved surface model database that provides the most accurate and transferable atomistic description of major alumina phases to date. The framework covers a-Al2O3, g-Al2O3, boehmite, diaspore, and gibbsite using a single, physically interpretable parameter set that is directly compatible with CHARMM, AMBER, OPLS-AA, CVFF, and PCFF. Across structural, thermodynamic, mechanical, and interfacial benchmarks, simulations reproduce experimental reference data with more than 95 percent accuracy, exceeding existing force fields and the reliability of current density-functional approaches. A key advance is the first transferable treatment of surface ionization and charge regulation across alumina phases over a broad range of pH values, enabling simulations of realistic solid electrolyte interfaces without phase-specific reparameterization. Quantitative reliability is demonstrated by reproducing trends in zeta potentials and pH-dependent adsorption of a corrosion inhibitor at alumina-water interfaces. Predicted adsorption free energies and surface contact times correlate with experiments across more than an order of magnitude. Relative to ML-DFT workflows, the speed 100 to 1000 times faster, reaching system sizes and time scales inaccessible to quantum methods. The results establish a predictive computational platform to design alumina-containing functional materials under realistic process conditions. △ Less

Submitted 18 January, 2026; originally announced January 2026.

Comments: 102 pages (52 main text, 50 SI), 9 figures main text, 14 Figures SI, 2 Tables main text, 8 Tables SI

Mechanics of axis formation in $\textit{Hydra}$

Authors: Arthur Hernandez, Cuncheng Zhu, Luca Giomi

Abstract: The emergence of a body axis is a fundamental step in the development of multicellular organisms. In simple systems such as $\textit{Hydra}$, growing evidence suggests that mechanical forces generated by collective cellular activity play a central role in this process. Here, we explore a physical mechanism for axis formation based on the coupling between active stresses and tissue elasticity. We a… ▽ More The emergence of a body axis is a fundamental step in the development of multicellular organisms. In simple systems such as $\textit{Hydra}$, growing evidence suggests that mechanical forces generated by collective cellular activity play a central role in this process. Here, we explore a physical mechanism for axis formation based on the coupling between active stresses and tissue elasticity. We analyse the elastic deformation induced by activity-generated stresses and show that, owing to the spherical topology of the tissue, forces globally condense toward configurations in which both elastic strain and nematic defect localise at opposite poles. These mechanically selected states define either a polar or apolar head-food axis. To characterize the condensed regime, we introduce a compact parametrization of of the active force and flux distributions, enabling analytical predictions and direct comparison with experiments. Using this framework, we calculate experimentally relevant observables, including areal strain, lateral pressure, and normal displacements during muscular contraction, as well as the detailed structure of topological defect complexes in head and foot regions. Together, our results identify a mechanical route by which active tissues can spontaneously break symmetry at the organismal scale, suggesting a general physical principle underlying body-axis specification during morphogenesis. △ Less

Submitted 8 January, 2026; originally announced January 2026.

Comments: 19 pages, 9 figures

Resolution and Robustness Bounds for Reconstructive Spectrometers

Authors: Changyan Zhu, Hsuan Lo, Jianbo Yu, Qijie Wang, Y. D. Chong

Abstract: Reconstructive spectrometers are a promising emerging class of devices that combine complex light scattering with inference to enable compact, high-resolution spectrometry. Thus far, the physical determinants of these devices' performance remain under-explored. We show that under a broad range of conditions, the noise-induced error for spectral reconstruction is governed by the Fisher information.… ▽ More Reconstructive spectrometers are a promising emerging class of devices that combine complex light scattering with inference to enable compact, high-resolution spectrometry. Thus far, the physical determinants of these devices' performance remain under-explored. We show that under a broad range of conditions, the noise-induced error for spectral reconstruction is governed by the Fisher information. We then use random matrix theory to derive a closed-form relation linking the variance bound to a set of key physical parameters: the spectral correlation length, the mean transmittance, and the number of frequency and measurement channels. The analysis reveals certain fundamental trade-offs between these physical parameters, and establishes the conditions for a spectrometer to achieve ``super-resolution'' below the limit set by the spectral correlation length. Our theory is confirmed using numerical validations with a random matrix model as well as full-wave simulations. These results establish a physically-grounded framework for designing and analyzing performant and noise-robust reconstructive spectrometers. △ Less

Submitted 27 July, 2026; v1 submitted 23 December, 2025; originally announced December 2025.

Comments: 15 pages, 8 figures. Includes Supplementary Materials

Development of a dual-phase xenon time projection chamber prototype for the RELICS experiment

Authors: Lingfeng Xie, Jiajun Liu, Yifei Zhao, Chang Cai, Guocai Chen, Jiangyu Chen, Huayu Dai, Rundong Fang, Hongrui Gao, Fei Gao, Jingfan Gu, Xiaoran Guo, Jiheng Guo, Chengjie Jia, Gaojun Jin, Fali Ju, Yanzhou Hao, Xu Han, Yang Lei, Kaihang Li, Meng Li, Minhua Li, Ruize Li, Shengchao Li, Siyin Li , et al. (28 additional authors not shown)

Abstract: The RELICS (REactor neutrino LIquid xenon Coherent elastic Scattering) experiment aims to detect coherent elastic neutrino-nucleus scattering from reactor antineutrinos using a dual-phase xenon time projection chamber. To validate the detector concept and ensure technical reliability for the full-scale experiment, a dedicated prototype was designed, constructed, and operated. This work presents an… ▽ More The RELICS (REactor neutrino LIquid xenon Coherent elastic Scattering) experiment aims to detect coherent elastic neutrino-nucleus scattering from reactor antineutrinos using a dual-phase xenon time projection chamber. To validate the detector concept and ensure technical reliability for the full-scale experiment, a dedicated prototype was designed, constructed, and operated. This work presents an overview of the design, construction, and operational performance of the prototype, with emphasis on its major subsystems, including the TPC, cryogenic and xenon purification systems, slow control, and data acquisition. During operation, the detector demonstrated the capability to achieve a sub-keV energy threshold required for the RELICS physics program, as reflected by a measured single electron gain of 34.30~$\pm$~0.01~(stat.)~PE/e$^-$ and the successful detection of 0.27~keV L-shell decay events from $^{37}$Ar. In addition, essential data analysis techniques and simulation frameworks were developed and validated, establishing the methodological foundation for future RELICS operations. The successful construction and operation of this prototype confirm the feasibility of the core technologies and provide a crucial experimental basis for the final RELICS detector. △ Less

Submitted 11 March, 2026; v1 submitted 23 November, 2025; originally announced November 2025.

Quantum optical neural networks using atom-cavity interactions to provide all-optical nonlinearity

Authors: Chuanzhou Zhu, Tianyu Wang, Peter L. McMahon, Daniel Soh

Abstract: Optical neural networks (ONNs) have been developed to enhance processing speed and energy efficiency in machine learning by leveraging optical devices for nonlinear activation and establishing connections among neurons. In this work, we propose a quantum optical neural network (QONN) that utilizes atom-cavity neurons with controllable photon absorption and emission. These quantum neurons are desig… ▽ More Optical neural networks (ONNs) have been developed to enhance processing speed and energy efficiency in machine learning by leveraging optical devices for nonlinear activation and establishing connections among neurons. In this work, we propose a quantum optical neural network (QONN) that utilizes atom-cavity neurons with controllable photon absorption and emission. These quantum neurons are designed to replace the electronic components in ONNs, which typically introduce delays and substantial energy consumption during nonlinear activation. To evaluate the performance of the QONN, we apply it to the MNIST digit classification task, considering the effects of photon absorption duration, random atom-cavity detuning, and stochastic photon loss. Additionally, we introduce a convolutional QONN to facilitate a real-world satellite image classification (SAT-6) task. Due to its compact hardware and low power consumption, the QONN offers a promising solution for real-time satellite sensing, reducing communication bandwidth with ground stations and thereby enhancing data security. △ Less

Submitted 30 July, 2026; v1 submitted 8 November, 2025; originally announced November 2025.

Journal ref: Physica Scripta 101, 305106 (2026)

Lithium Niobate Vertical Cavity Electro-Optic Modulator

Authors: Jikun Liu, Weiye Liu, Wei Wu, Ziang Guo, Changrui Zhu, Lun Qu, Pengfei Zhu, Yiting Zhang, Zhihao Chen, Qinglian Li, Dahuai Zheng, Hongde Liu, Shaowei Wang, Wei Cai, Mengxin Ren, Jingjun Xu

Abstract: Electro-optic modulators (EOMs) are vital for optical imaging and information processing, with free-space devices enabling LiDAR and beam control. Lithium niobate (LN), powered by the strong Pockels effect and scalable LN-on-insulator (LNOI) platform, has become a leading material for high-performance EOMs. Here we realize a vertical-cavity EOM in which an LN membrane is sandwiched between two pho… ▽ More Electro-optic modulators (EOMs) are vital for optical imaging and information processing, with free-space devices enabling LiDAR and beam control. Lithium niobate (LN), powered by the strong Pockels effect and scalable LN-on-insulator (LNOI) platform, has become a leading material for high-performance EOMs. Here we realize a vertical-cavity EOM in which an LN membrane is sandwiched between two photonic crystal (PhC) mirrors with integrated electrodes. The cavity supports sharp defect-mode resonances that shift efficiently under the Pockels effect, enabling strong modulation of transmission. Experiments show a depth of 43 % at 50 V and a bandwidth of 5 MHz. This architecture combines free-space compatibility with fabrication simplicity, opening new routes to compact electro-optic platforms for ranging, holography, and beam steering. △ Less

Submitted 3 November, 2025; originally announced November 2025.

Comments: 7 pages, 4 figures

Design and characterization of a photosensor system for the RELICS experiment

Authors: Jijun Yang, Ruize Li, Chang Cai, Guocai Chen, Jiangyu Chen, Huayu Dai, Rundong Fang, Fei Gao, Jingfan Gu, Xiaoran Guo, Jiheng Guo, Gaojun Jin, Fali Ju, Yanzhou Hao, Yang Lei, Kaihang Li, Meng Li, Minhua Li, Shengchao Li, Siyin Li, Tao Li, Qing Lin, Jiajun Liu, Sheng Lv, Guang Luo , et al. (23 additional authors not shown)

Abstract: In this paper, we present the design and characterization of a photosensor system developed for the RELICS experiment. An extended dynamic range base was designed to mitigate photomultiplier tube (PMT) saturation caused by intense cosmic muon backgrounds in the surface-level RELICS detector. The system employs dual readout from the anode and the seventh dynode to extend the linear response range o… ▽ More In this paper, we present the design and characterization of a photosensor system developed for the RELICS experiment. An extended dynamic range base was designed to mitigate photomultiplier tube (PMT) saturation caused by intense cosmic muon backgrounds in the surface-level RELICS detector. The system employs dual readout from the anode and the seventh dynode to extend the linear response range of the PMT. In particular, our characterization and measurements of Hamamatsu R8520-406 PMTs confirm stable operation under positive high-voltage bias, extending the linear response range by more than an order of magnitude. Furthermore, a model of PMT saturation and recovery was developed to evaluate the influence of cosmic muon signals in the RELICS detector. The results demonstrate the system capability to detect coherent elastic neutrino-nucleus scattering signals under surface-level cosmic backgrounds, and suggest the potential to extend the scientific reach of RELICS to MeV-scale interactions. △ Less

Submitted 19 February, 2026; v1 submitted 28 October, 2025; originally announced October 2025.

Comments: 19 pages, 13 figures. v3: updated to address the referees' comments, fixed author list typo. Journal reference added

Journal ref: JINST 21 (2026) 2, P02039

Purcell-enhanced single-photon generation from CsPbBr$_3$ quantum dots in in-situ selected Laguerre-Gaussian modes

Authors: Virginia Oddi, Darius Urbonas, Etsuki Kobiyama, Ioannis Georgakilas, Ihor Cherniukh, Kseniia Shcherbak, Chenglian Zhu, Maryna I. Bodnarchuk, Maksym V. Kovalenko, Rainer F. Mahrt, Gabriele Rainò, Thilo Stöferle

Abstract: Single photons in Laguerre-Gaussian (LG) beams, which carry orbital angular momentum (OAM), could enable more robust and efficient photonic quantum communication and information processing, as well as enhanced sensitivity in quantum metrology and imaging. However, as most implementations are indirect or require additional mode-shaping elements, direct generation of single photons with OAM has rece… ▽ More Single photons in Laguerre-Gaussian (LG) beams, which carry orbital angular momentum (OAM), could enable more robust and efficient photonic quantum communication and information processing, as well as enhanced sensitivity in quantum metrology and imaging. However, as most implementations are indirect or require additional mode-shaping elements, direct generation of single photons with OAM has received growing interest. Colloidal lead halide perovskite quantum dots (QDs) have recently emerged as a versatile material that can produce indistinguishable single photons quasi-deterministically at high rate. Here, we integrate single CsPbBr$_3$ QDs into an open Fabry-Perot microcavity with a nanofabricated Gaussian-shaped deformation, demonstrating Purcell-enhanced single-photon generation into individual cavity modes with up to 18.1 $\pm$ 0.2 times accelerated decay, down to tens of picoseconds. By in-situ tuning of the cavity resonance, we can selectively couple a single QD to different LG modes carrying OAM and observe the spatial patterns of the generated single-photon beams emitted from the cavity. Our findings open the door to high photon rate sources that directly generate single-photon LG beams for advanced quantum photonic applications. △ Less

Submitted 2 October, 2025; originally announced October 2025.

Journal ref: ACS Nano 20, 6167 (2026)

Typhoon Tracks Regulated by Feedbacks of Fine-Scale Clouds to Environment

Authors: Haoran Zhao, Shaoqing Zhang, Yang Gao, Lixin Wu, Yihan Cao, Wenju Cai, Bin Wang, L. Ruby Leung, Zebin Lu, Zhong Zhong, Xiaolin Yu, Mingkui Li, Chenyu Zhu

Abstract: Accurate tropical cyclone (TC) track prediction is crucial for mitigating the catastrophic impacts of TCs on human life and the environment. Despite decades of research on tropical cyclone (TC) track prediction, large errors known as track forecast busts (TFBs) occur frequently, and their causes remain poorly understood. Here, we examine a few dozens of TCs using a unique TC downscaling strategy t… ▽ More Accurate tropical cyclone (TC) track prediction is crucial for mitigating the catastrophic impacts of TCs on human life and the environment. Despite decades of research on tropical cyclone (TC) track prediction, large errors known as track forecast busts (TFBs) occur frequently, and their causes remain poorly understood. Here, we examine a few dozens of TCs using a unique TC downscaling strategy that can quantitatively assess the sensitivity of TC track on the strength of feedbacks of fine-scale clouds to environment. We show that as TFBs have a weaker environmental steering that favors scattering cumulonimbus clouds, capturing asymmetric distribution of planetary vorticity advection induced by such fine-scale clouds corrects TFBs by 60 percent. Our clear identification of such important TC track predictability source promises continuous improvement of TC track prediction as finer-scale TC clouds and their interactions with environment are better resolved as model larger-scale behaviors have improved. △ Less

Submitted 30 September, 2025; originally announced September 2025.

Comments: 41 pages, 13 figures

Wavelength-scale noise-resistant on-chip spectrometer

Authors: Jianbo Yu, Hsuan Lo, Wenduo Chen, Changyan Zhu, Yujin Wu, Fakun Wang, Chongwu Wang, Congliao Yan, Cuong Dang, Bihan Wen, Hui Cao, Yidong Chong, Qi Jie Wang

Abstract: Performant on-chip spectrometers are important for advancing sensing technologies, from environmental monitoring to biomedical diagnostics. As device footprints approach the scale of the operating wavelength, previously strategies, including those relying on multiple scattering in diffusive media, face fundamental accuracy constraints tied to limited optical path lengths. Here, we demonstrate a wa… ▽ More Performant on-chip spectrometers are important for advancing sensing technologies, from environmental monitoring to biomedical diagnostics. As device footprints approach the scale of the operating wavelength, previously strategies, including those relying on multiple scattering in diffusive media, face fundamental accuracy constraints tied to limited optical path lengths. Here, we demonstrate a wavelength-scale, CMOS-compatible on-chip spectrometer that overcomes this challenge by exploiting inverse-designed quasinormal modes in a complex photonic resonator. These modes extend the effective optical path length beyond the physical device dimensions, producing highly de-correlated spectral responses. We show that this strategy is theoretically optimal for minimizing spectral reconstruction error in the presence of measurement noise. The fabricated spectrometer occupies a lateral footprint of only 3.5 times the free-space operating wavelength, with a spectral resolution of 10 nm across the 3.59-3.76 micrometer mid-infrared band, which is suitable for molecular sensing. The design of this miniaturized noise-resistant spectrometer is readily extensible to other portions of the electromagnetic spectrum, paving the way for lab-on-a-chip devices, chemical sensors, and other applications. △ Less

Submitted 30 September, 2025; v1 submitted 26 September, 2025; originally announced September 2025.

Comments: 17 pages, 5 figures

Mechanisms of isotope exchange between aqueous solutions and barite in low-temperature geochemical systems

Authors: Chen Zhu, Youxue Zhang, Donald J. DePaolo, Kaiyun Chen, Honglin Yuan, Tao Yang, Lei Gong

Abstract: The prevailing view that solid-state diffusion is negligible at low temperatures is challenged by rapid sulfur and barium isotope exchange between natural barite crystals and aqueous solutions in laboratory experiments. This assumption relies on diffusivities extrapolated from high-temperature experiments. Here, isotope exchange rates were measured in solutions enriched with 137Ba and 32S at 50 an… ▽ More The prevailing view that solid-state diffusion is negligible at low temperatures is challenged by rapid sulfur and barium isotope exchange between natural barite crystals and aqueous solutions in laboratory experiments. This assumption relies on diffusivities extrapolated from high-temperature experiments. Here, isotope exchange rates were measured in solutions enriched with 137Ba and 32S at 50 and 80 oC for less than 10,360 hours. SIMS depth profiles revealed 137Ba enrichment to ~75 nm, with shapes characteristic of classical diffusion. Isotope disequilibrium between the barite surface and aqueous solution implies a continuous supply from the interior. These results indicate that defects and vacancies in barite and similar low-temperature minerals enable effective solid-state diffusion, with profound implications for paleoenvironmental reconstructions, materials science, and engineering. △ Less

Submitted 14 September, 2025; originally announced September 2025.

First Production of Skipper-CCD Modules for the DAMIC-M Experiment

Authors: H. Lin, M. Traina, S. Paul, K. Aggarwal, I. Arnquist, N. Castello-Mor, A. E. Chavarria, M. Conde, C. De Dominicis, M. Huehn, S. Hope, T. Hossbach, L. Iddir, I. Lawson, R. Lou, S. Munagavalasa, D. Norcini, P. Privitera, B. Roach, R. Roehnelt, N. Rocco, R. Saldanha, T. Schleider, R. Smida, B. Stillwell , et al. (43 additional authors not shown)

Abstract: The DAMIC-M experiment will search for sub-GeV dark matter particles with a large array of silicon skipper charge-coupled devices (CCDs) at the Modane Underground Laboratory (LSM) in France. After five years of development, we recently completed the production of 28 CCD modules at the University of Washington, each consisting of four 9-megapixel skipper CCDs. Material screening and background cont… ▽ More The DAMIC-M experiment will search for sub-GeV dark matter particles with a large array of silicon skipper charge-coupled devices (CCDs) at the Modane Underground Laboratory (LSM) in France. After five years of development, we recently completed the production of 28 CCD modules at the University of Washington, each consisting of four 9-megapixel skipper CCDs. Material screening and background controls were implemented to meet stringent radio-purity targets, while extensive testing was employed to select science-grade CCDs for the modules and confirm their excellent performance after fabrication. Further testing at LSM will select 26 of these modules (${\sim}$350 g active mass) to be installed and operated in the DAMIC-M detector in early 2026. △ Less

Submitted 8 September, 2025; originally announced September 2025.

Comments: 39 pages, 25 figures

Data-driven solar forecasting enables near-optimal economic decisions

Authors: Zhixiang Dai, Minghao Yin, Xuanhong Chen, Alberto Carpentieri, Jussi Leinonen, Boris Bonev, Chengzhe Zhong, Thorsten Kurth, Jingan Sun, Ram Cherukuri, Yuzhou Zhang, Ruihua Zhang, Farah Hariri, Xiaodong Ding, Chuanxiang Zhu, Dake Zhang, Yaodan Cui, Yuxi Lu, Yue Song, Bin He, Jie Chen, Yixin Zhu, Chenheng Xu, Maofeng Liu, Zeyi Niu , et al. (5 additional authors not shown)

Abstract: Solar energy adoption is critical to achieving net-zero emissions. However, it remains difficult for many industrial and commercial actors to decide on whether they should adopt distributed solar-battery systems, which is largely due to the unavailability of fast, low-cost, and high-resolution irradiance forecasts. Here, we present SunCastNet, a lightweight data-driven forecasting system that prov… ▽ More Solar energy adoption is critical to achieving net-zero emissions. However, it remains difficult for many industrial and commercial actors to decide on whether they should adopt distributed solar-battery systems, which is largely due to the unavailability of fast, low-cost, and high-resolution irradiance forecasts. Here, we present SunCastNet, a lightweight data-driven forecasting system that provides 0.05$^\circ$, 10-minute resolution predictions of surface solar radiation downwards (SSRD) up to 7 days ahead. SunCastNet, coupled with reinforcement learning (RL) for battery scheduling, reduces operational regret by 76--93\% compared to robust decision making (RDM). In 25-year investment backtests, it enables up to five of ten high-emitting industrial sectors per region to cross the commercial viability threshold of 12\% Internal Rate of Return (IRR). These results show that high-resolution, long-horizon solar forecasts can directly translate into measurable economic gains, supporting near-optimal energy operations and accelerating renewable deployment. △ Less

Submitted 8 September, 2025; originally announced September 2025.

Comments: Main text ~12 pages, 4 figures, 0 tables

Projection-Based Solver for Viscoelastic Stokes Flow using FFTs

Authors: Georg Rempfer, Mae Nesenberend, Chengkai Zhu, Bart Stam, Debabrata Panja, Joost de Graaf

Abstract: Understanding the flow of complex media is relevant for a wide range of research fields and industrial applications. Several numerical approaches exist by which approximate solutions can be determined for the Stokes equations that describe microhydrodynamic flows at the continuum level. However, achieving efficiency and accuracy for an incompressible fluid remains challenging. Here, we present an… ▽ More Understanding the flow of complex media is relevant for a wide range of research fields and industrial applications. Several numerical approaches exist by which approximate solutions can be determined for the Stokes equations that describe microhydrodynamic flows at the continuum level. However, achieving efficiency and accuracy for an incompressible fluid remains challenging. Here, we present an algorithm for solving the Stokes equations for an Oldroyd-B fluid using Fourier transforms. We gain efficiency by leveraging the 'Fastest Fourier Transform in the West' (FFTW). We validate our approach for the well-characterized four-roll mill, which exhibits nearly singular points of stress at the extensional points of the flow. We capture this divergence and showcase the potential of our method without making the usual diffusive renormalization. We also focus on characterizing the power-law behavior and numerically assess the divergence criterion. Future work will concentrate on active systems, the introduction of moving boundaries, and application to microfluidic devices. △ Less

Submitted 6 August, 2026; v1 submitted 1 September, 2025; originally announced September 2025.

Comments: 11 pages, 7 figures

Cavity-less Brillouin strong coupling in a solid-state continuous system

Authors: Laura Blázquez Martínez, Changlong Zhu, Birgit Stiller

Abstract: Strongly coupling two systems allows them to exchange coherent information before the systems decohere. This important regime in light-matter interactions has predominantly been reached in optical resonator configurations. In this work, we present the experimental realization of strong coupling between optical and acoustic fields within a continuum of modes in a cavity-less configuration after a s… ▽ More Strongly coupling two systems allows them to exchange coherent information before the systems decohere. This important regime in light-matter interactions has predominantly been reached in optical resonator configurations. In this work, we present the experimental realization of strong coupling between optical and acoustic fields within a continuum of modes in a cavity-less configuration after a single-pass through an optical waveguide. The underlying physical effect of anti-Stokes Brillouin-Mandelstam scattering in a highly nonlinear fiber at T = 4 K allows us to experimentally demonstrate strong coupling in a waveguide scenario. We show the splitting of the optoacoustic spectral response and introduce a novel technique to measure the avoided crossing of hybrid optoacoustic modes via forced detuning. This demonstration opens a path towards in-line acoustic-waves-based quantum signal processing in waveguide systems. △ Less

Submitted 17 July, 2025; v1 submitted 11 July, 2025; originally announced July 2025.

Comments: Updated version: reference list updated, Fig. 1 increased in size for readability; 6 pages, 4 figures

High-Performance Ultra-Wide-Bandgap CaSnO3 Metal-Oxide-Semiconductor Field-Effect Transistors

Authors: Weideng Sun, Junghyun Koo, Donghwan Kim, Hongseung Lee, Rishi Raj, Chengyu Zhu, Kiyoung Lee, Andre Mkhoyan, Hagyoul Bae, Bharat Jalan, Gang Qiu

Abstract: The increasing demand for high-voltage and high-power electronic applications has intensified the search for novel ultrawide bandgap (UWB) semiconductors. Alkaline earth stannates possess wide band gaps and exhibit the highest room-temperature electron mobilities among all perovskite oxides. Among this family, Calcium stannate (CaSnO3) has the largest band gap of ~4.7 eV, holding great promise for… ▽ More The increasing demand for high-voltage and high-power electronic applications has intensified the search for novel ultrawide bandgap (UWB) semiconductors. Alkaline earth stannates possess wide band gaps and exhibit the highest room-temperature electron mobilities among all perovskite oxides. Among this family, Calcium stannate (CaSnO3) has the largest band gap of ~4.7 eV, holding great promise for high-power applications. However, the demonstration of CaSnO3 power electronic devices is so far limited. In this work, high-performance metal-oxide-semiconductor field-effect transistor (MOSFET) devices based on La-doped CaSnO3 are demonstrated for the first time. The MOSFETs exhibit an on/off ratio exceeding 10^8, along with field-effect mobility of 8.4 cm2 V-1 s-1 and on-state current of 30 mA mm-1. The high performance of the CaSnO3 MOSFET devices can be ascribed to the excellent metal-to-semiconductor contact resistance of 0.73 kΩμm. The devices also show great potential for harsh environment operations, as high-temperature operations up to 400 K have been demonstrated. An off-state breakdown voltage of 1660 V is achieved, with a breakdown field of ~8.3 MV cm-1 among the highest reported for all UWB semiconductors. This work represents significant progress toward realizing the practical application of CaSnO3 in future high-voltage power electronic technologies. △ Less

Submitted 30 June, 2025; originally announced June 2025.

Simulating fluid vortex interactions on a superconducting quantum processor

Authors: Ziteng Wang, Jiarun Zhong, Ke Wang, Zitian Zhu, Zehang Bao, Chenjia Zhu, Wenwen Zhao, Yaomin Zhao, Yue Yang, Chao Song, Shiying Xiong

Abstract: Vortex interactions are commonly observed in atmospheric turbulence, plasma dynamics, and collective behaviors in biological systems. However, accurately simulating these complex interactions is highly challenging due to the need to capture fine-scale details over extended timescales, which places computational burdens on traditional methods. In this study, we introduce a quantum vortex method, re… ▽ More Vortex interactions are commonly observed in atmospheric turbulence, plasma dynamics, and collective behaviors in biological systems. However, accurately simulating these complex interactions is highly challenging due to the need to capture fine-scale details over extended timescales, which places computational burdens on traditional methods. In this study, we introduce a quantum vortex method, reformulating the Navier--Stokes (NS) equations within a quantum mechanical framework to enable the simulation of multi-vortex interactions on a quantum computer. We construct the effective Hamiltonian for the vortex system and implement a spatiotemporal evolution circuit to simulate its dynamics over prolonged periods. By leveraging eight qubits on a superconducting quantum processor with gate fidelities of 99.97\% for single-qubit gates and 99.76\% for two-qubit gates, we successfully reproduce natural vortex interactions. This method bridges classical fluid dynamics and quantum computing, offering a novel computational platform for studying vortex dynamics. Our results demonstrate the potential of quantum computing to tackle longstanding challenges in fluid dynamics and broaden applications across both natural and engineering systems. △ Less

Submitted 4 June, 2025; originally announced June 2025.

Comments: 19 pages, 10 figures

Attosecond transient absorption spectroscopy in monolayer hexagonal boron nitride

Authors: Jiayu Yan, Chenkai Zhu, Rongxiang Zhang, Xiaohui Zhao, Fulong Dong

Abstract: We simulate the attosecond transient absorption spectroscopy (ATAS) of monolayer hexagonal boron nitride (hBN) using the time-dependent density functional theory and two-band density-matrix equations within the tight-binding approximation. The simulation results from the two methods are qualitatively consistent. We focus on the fishbone structure around the gap energy of the M point, which exhibit… ▽ More We simulate the attosecond transient absorption spectroscopy (ATAS) of monolayer hexagonal boron nitride (hBN) using the time-dependent density functional theory and two-band density-matrix equations within the tight-binding approximation. The simulation results from the two methods are qualitatively consistent. We focus on the fishbone structure around the gap energy of the M point, which exhibits a temporal period equal to that of the pump laser. To gain deeper insight into this structure, we simplify the two-band model to a single-electron model located at the M point, allowing us to derive an analytical expression that can qualitatively reproduce the numerical results. By isolating the influence of the Berry connection on the ATAS, our analytical results reveal that both the interband transition dipole moments and the Berry connection play important roles in the fishbone structure of the ATAS. Moreover, we also have investigated the dependence of ATAS on the gap energy based the tight-binding approximation. The results demonstrate that the ATAS intensity is enhanced as the gap energy increases, in agreement with our analytical prediction. Our study may shed light on the generation mechanism of the fishbone structure of the ATAS in hBN. △ Less

Submitted 31 July, 2025; v1 submitted 15 May, 2025; originally announced May 2025.

Quantum state discrimination in a $\mathcal{PT}$-symmetric system of a single trapped ion

Authors: Chenhao Zhu, Tingting Shi, Liangyu Ding, Zhiyue Zheng, Xiang Zhang, Wei Zhang

Abstract: We experimentally demonstrate an unambiguous quantum state discrimination of two qubit states under a non-Hermitian Hamiltonian with parity-time-reversal ($\mathcal{PT}$) symmetry in a single trapped $^{40}$Ca$^+$ ion. We show that any two non-orthogonal states can become orthogonal subjected to time evolution of a $\mathcal{PT}$-symmetric Hamiltonian in both the $\mathcal{PT}$-symmetry preserving… ▽ More We experimentally demonstrate an unambiguous quantum state discrimination of two qubit states under a non-Hermitian Hamiltonian with parity-time-reversal ($\mathcal{PT}$) symmetry in a single trapped $^{40}$Ca$^+$ ion. We show that any two non-orthogonal states can become orthogonal subjected to time evolution of a $\mathcal{PT}$-symmetric Hamiltonian in both the $\mathcal{PT}$-symmetry preserving and broken regimes, thus can be discriminated deterministically. For a given pair of candidate states, we show that the parameters of the Hamiltonian must be confined in a proper range, within which there exists an optimal choice to realize quantum brachistochrone for the fastest orthogonalization. Besides, we provide a clear geometric picture and some analytic results to understand the main conclusions. Our work shows a promising application of non-Hermitian physics in quantum information processing. △ Less

Submitted 28 February, 2025; originally announced February 2025.

Comments: 6 pages, 4 figures

Quantum implicit representation of vortex filaments in turbulence

Authors: Chenjia Zhu, Ziteng Wang, Shiying Xiong, Yaomin Zhao, Yue Yang

Abstract: Entangled vortex filaments are essential to turbulence, serving as coherent structures that govern nonlinear fluid dynamics and support the reconstruction of fluid fields to reveal statistical properties. This study introduces an quantum implicit representation of vortex filaments in turbulence, employing a level-set method that models the filaments as the intersection of the real and imaginary ze… ▽ More Entangled vortex filaments are essential to turbulence, serving as coherent structures that govern nonlinear fluid dynamics and support the reconstruction of fluid fields to reveal statistical properties. This study introduces an quantum implicit representation of vortex filaments in turbulence, employing a level-set method that models the filaments as the intersection of the real and imaginary zero iso-surfaces of a complex scalar field. Describing the fluid field via the scalar field offers distinct advantages in capturing complex structures, topological properties, and fluid dynamics, while opening new avenues for innovative solutions through quantum computing platforms. The representation is reformulated into an eigenvalue problem for Hermitian matrices, enabling the conversion of velocity fields into complex scalar fields that embed the vortex filaments. The resulting optimization is addressed using a variational quantum eigensolver, with Pauli operator truncation and deep learning techniques applied to improve efficiency and reduce noise. The proposed quantum framework achieves a near-linear time complexity and a exponential storage reduction while maintaining a balance of accuracy, robustness, and versatility, presenting a promising tool for turbulence analysis, vortex dynamics research, and machine learning dataset generation. △ Less

Submitted 5 September, 2025; v1 submitted 25 February, 2025; originally announced February 2025.

Journal ref: J. Fluid Mech. 1014 (2025) A31

Optimizing stellarators with hidden symmetry

Authors: Hengqian Liu, Guodong Yu, Caoxiang Zhu, José Luis Velasco, Rahul Gaur, Dario Panici, Egemen Kolemen, Mingyang Yu, Weixing Ding, Shaojie Wang, Ge Zhuang

Abstract: Stellarators confine fusion plasmas using three-dimensional magnetic fields composed of nested toroidal magnetic surfaces. In generic stellarators, trapped particles can drift across these surfaces and degrade plasma confinement. Certain topological properties of the magnetic field strength can suppress these drifts. However, conventional stellarator design approaches typically enforce restrictive… ▽ More Stellarators confine fusion plasmas using three-dimensional magnetic fields composed of nested toroidal magnetic surfaces. In generic stellarators, trapped particles can drift across these surfaces and degrade plasma confinement. Certain topological properties of the magnetic field strength can suppress these drifts. However, conventional stellarator design approaches typically enforce restrictive constraints to realize such properties, thereby segmenting and limiting the accessible configuration space. In this work, we reformulate the conditions for efficient confinement as constraints on a homeomorphic straightening transformation of the field contours. Within this framework, the various families of stellarator magnetic fields optimized for plasma confinement arise naturally as specific realizations of a unified mapping. This new perspective provides a significantly more comprehensive description of viable stellarator configurations, enabling systematic exploration of trade-offs among confinement quality, geometric complexity, and engineering requirements. We illustrate this approach by presenting a highly compact stellarator design that nevertheless achieves plasma performance comparable to that of leading reactor-scale designs with much larger aspect ratios. △ Less

Submitted 21 March, 2026; v1 submitted 13 February, 2025; originally announced February 2025.

Comments: 27 pages, 6 figures

Distinct terahertz third-harmonic generation of many-body excitonic states

Authors: Changqing Zhu, Anneke Reinold, Patrick Pilch, Sergey Kovalev, Julian Heckötter, Doris Reiter, Manfred Bayer, Marc Assmann, Zhe Wang

Abstract: The dynamics of an electron-hole plasma governed by strong Coulomb interaction is a challenging many-body problem.We report on experimental realization of electron-hole many-body states in the picosecond time scale, with tunable densities in a representative semiconductor Cu$_2$O. By using time-resolved optical-pump terahertz third-harmonic-generation spectroscopy, we study the nonlinear terahertz… ▽ More The dynamics of an electron-hole plasma governed by strong Coulomb interaction is a challenging many-body problem.We report on experimental realization of electron-hole many-body states in the picosecond time scale, with tunable densities in a representative semiconductor Cu$_2$O. By using time-resolved optical-pump terahertz third-harmonic-generation spectroscopy, we study the nonlinear terahertz dynamical characteristics of the many-body electron-hole states. We find not only efficient and nonperturbative terahertz third-harmonic yield associated with the excitonic formation, but also a nonmonotonic dependence of the excitonic nonlinear response on the electron-hole density, reflecting the exciton dissociation at high charge density. Our results provide an efficient excitonic sensing of the far-from-equilibrium electron-hole many-body states. △ Less

Submitted 16 January, 2025; originally announced January 2025.

Comments: 5 pages, 4 figures

Journal ref: Phys. Rev. Lett. 134, 196503 (2025)

Terahertz electro-optic Kerr effect in LaAlO3

Authors: Sergey Kovalev, Changqing Zhu, Anneke Reinold, Max Koch, Zirui Wang, Patrick Pilch, Ahmed Ghalgaoui, Siyu Duan, Cong Li, Jianbing Zhang, Pu Yu, Zhe Wang

Abstract: In this letter, we investigate the terahertz (THz) electro-optic Kerr effect (KE) dynamics in LaAlO3 (LAO), a widely used substrate for thin film preparation. We show that the KE dynamics strongly depend on the material anisotropy due to interference between THz field-induced and strain-induced optical birefringence. Such interference leads to quasi-phase matching conditions of the KE, which becom… ▽ More In this letter, we investigate the terahertz (THz) electro-optic Kerr effect (KE) dynamics in LaAlO3 (LAO), a widely used substrate for thin film preparation. We show that the KE dynamics strongly depend on the material anisotropy due to interference between THz field-induced and strain-induced optical birefringence. Such interference leads to quasi-phase matching conditions of the KE, which becomes strongly frequency dependent. Depending on the THz frequency, the KE exhibits a uni- and bipolar shape of the quadratic response. The demonstrated effects will be present in a wide variety of materials used as substrates in different THz-pump laser-probe experiments and need to be considered in order to disentangle the different contributions to the measured ultrafast dynamic signals. △ Less

Submitted 8 January, 2025; originally announced January 2025.

Comments: 4 pages, 4 figures

High-gain optical parametric amplification with a continuous-wave pump using a domain-engineered thin-film lithium niobate waveguide

Authors: Mengwen Chen, Chenyu Wang, Kunpeng Jia, Xiao-Hui Tian, Jie Tang, Chunxi Zhu, Xiaowen Gu, Zexing Zhao, Zikang Wang, Zhilin Ye, Ji Tang, Yong Zhang, Zhong Yan, Xuewen Wang, Guang Qian, Biaobing Jin, Zhenlin Wang, Shi-Ning Zhu, Zhenda Xie

Abstract: While thin film lithium niobate (TFLN) is known for efficient signal generation, on-chip signal amplification remains challenging from fully integrated optical communication circuits. Here we demonstrate the continuous-wave-pump optical parametric amplification (OPA) using an x-cut domain-engineered TFLN waveguide, with high gain over the telecom band up to 13.9 dB, and test it for high signal-to-… ▽ More While thin film lithium niobate (TFLN) is known for efficient signal generation, on-chip signal amplification remains challenging from fully integrated optical communication circuits. Here we demonstrate the continuous-wave-pump optical parametric amplification (OPA) using an x-cut domain-engineered TFLN waveguide, with high gain over the telecom band up to 13.9 dB, and test it for high signal-to-noise ratio signal amplification using a commercial optical communication module pair. Fabricated in wafer scale using common process as devices including modulators, this OPA device marks an important step in TFLN photonic integration. △ Less

Submitted 31 July, 2025; v1 submitted 16 November, 2024; originally announced November 2024.

DarkSHINE Baseline Design Report: Physics Prospects and Detector Technologies

Authors: Jing Chen, Ji-Yuan Chen, Jun-Feng Chen, Xiang Chen, Chang-Bo Fu, Jun Guo, Yi-Han Guo, Kim Siang Khaw, Jia-Lin Li, Liang Li, Shu Li, Yu-ming Lin, Dan-Ning Liu, Kang Liu, Kun Liu, Qi-Bin Liu, Zhi Liu, Ze-Jia Lu, Meng Lv, Si-Yuan Song, Tong Sun, Jian-Nan Tang, Wei-Shi Wan, Dong Wang, Xiao-Long Wang , et al. (17 additional authors not shown)

Abstract: DarkSHINE is a newly proposed fixed-target experiment initiative to search for the invisible decay of Dark Photon via missing energy/momentum signatures, based on the high repetition rate electron beam to be deployed/delivered by the Shanghai High repetition rate XFEL and Extreme light facility (SHINE). This report elaborates the baseline design of DarkSHINE experiment by introducing the physics g… ▽ More DarkSHINE is a newly proposed fixed-target experiment initiative to search for the invisible decay of Dark Photon via missing energy/momentum signatures, based on the high repetition rate electron beam to be deployed/delivered by the Shanghai High repetition rate XFEL and Extreme light facility (SHINE). This report elaborates the baseline design of DarkSHINE experiment by introducing the physics goals, experimental setups, details of each sub-detector system technical designs, signal and backgground modelings, expected search sensitivities and future prospects, which mark an important step towards the further prototyping and technical demonstrations. △ Less

Submitted 3 December, 2024; v1 submitted 14 November, 2024; originally announced November 2024.

Transition between cooperative emission regimes in giant perovskite nanocrystals

Authors: Etsuki Kobiyama, Gabriele Rainò, Yuliia Berezovska, Chenglian Zhu, Simon C. Boehme, Maryna I. Bodnarchuk, Rainer F. Mahrt, Maksym V. Kovalenko, Thilo Stöferle

Abstract: Interactions between emitters within an ensemble can give rise to cooperative processes that significantly alter the properties of the emitted light. One such process is superfluorescence (SF), where excited electric dipoles spontaneously couple coherently and effectively radiate as one macroscopic emitter. It requires low energetic disorder, high temporal coherence and oscillator strength, and su… ▽ More Interactions between emitters within an ensemble can give rise to cooperative processes that significantly alter the properties of the emitted light. One such process is superfluorescence (SF), where excited electric dipoles spontaneously couple coherently and effectively radiate as one macroscopic emitter. It requires low energetic disorder, high temporal coherence and oscillator strength, and sub-wavelength volumes of material can be sufficient. Conversely, amplified spontaneous emission (ASE) originates from an avalanche-like stimulated amplification of initially spontaneously emitted photons and does not necessitate temporally coherent interactions among the emitters, but rather requires spatially long enough light propagation within the material to harvest the optical gain. Cesium lead halide perovskite nanocrystals (NCs) are one of the very few materials where both ASE (in disordered films) and SF (in ordered assemblies) were observed, however leaving unclear whether and how these regimes could be connected. Here, we demonstrate that temperature and excitation density can drive the transition between both regimes in a thin film of giant CsPbBr3 perovskite NCs. At temperatures below 45 K, excitonic SF was observed, whereas above a transition range between 45 K and 100 K, ASE prevails, but requires increased optical excitation and emitter density. Our results work out the different collective effects present in lead halide perovskites, providing fundamental insights into cooperative phenomena and important guidance for the development of compact and bright (quantum) light sources. △ Less

Submitted 7 October, 2024; originally announced October 2024.

Journal ref: Nature Materials 25, 1146-1153 (2026)

Neural Network-Based Multimode Fiber Imaging and Characterization Under Thermal Perturbations

Authors: Kun Wang, Changyan Zhu, Ennio Colicchia, Xingchen Dong, Wolfgang Kurz, Yosuke Mizuno, Martin Jakobi, Alexander W. Koch, Yidong Chong

Abstract: Multimode fiber (MMF) imaging aided by machine learning holds promise for numerous applications, including medical endoscopy. A key challenge for this technology is the sensitivity of modal transmission characteristics to environmental perturbations. Here, we show experimentally that an MMF imaging scheme based on a neural network (NN) can achieve results that are significantly robust to thermal p… ▽ More Multimode fiber (MMF) imaging aided by machine learning holds promise for numerous applications, including medical endoscopy. A key challenge for this technology is the sensitivity of modal transmission characteristics to environmental perturbations. Here, we show experimentally that an MMF imaging scheme based on a neural network (NN) can achieve results that are significantly robust to thermal perturbations. For example, natural images are successfully reconstructed as the MMF's temperature is varied by up to 50$^{\circ}$C relative to the training scenario, despite substantial variations in the speckle patterns caused by thermal changes. A dense NN with a single hidden layer is found to outperform a convolutional NN suitable for standard computer vision tasks. In addition, we demonstrate that NN parameters can be used to understand the MMF properties by reconstructing the approximate transmission matrices, and we show that the image reconstruction accuracy is directly related to the temperature dependence of the MMF's transmission characteristics. △ Less

Submitted 25 September, 2024; v1 submitted 24 September, 2024; originally announced September 2024.

Comments: 11 pages, 5 figures

Stokes flow of an evolving fluid film with arbitrary shape and topology

Authors: Cuncheng Zhu, David Saintillan, Albert Chern

Abstract: The dynamics of evolving fluid films in the viscous Stokes limit is relevant to various applications, such as the modeling of lipid bilayers in cells. While the governing equations were formulated by Scriven in 1960, solving for the flow of a deformable viscous surface with arbitrary shape and topology has remained a challenge. In this study, we present a straightforward discrete model based on va… ▽ More The dynamics of evolving fluid films in the viscous Stokes limit is relevant to various applications, such as the modeling of lipid bilayers in cells. While the governing equations were formulated by Scriven in 1960, solving for the flow of a deformable viscous surface with arbitrary shape and topology has remained a challenge. In this study, we present a straightforward discrete model based on variational principles to address this long-standing problem. We replace the classical equations, which are expressed with tensor calculus in local coordinates, with a simple coordinate-free, differential-geometric formulation. The formulation provides a fundamental understanding of the underlying mechanics and directly translates to discretization. We construct a discrete analogue of the system using the Onsager variational principle, which, in a smooth context, governs the flow of a viscous medium. In the discrete setting, instead of term-wise discretizing the coordinate-based Stokes equations, we construct a discrete Rayleighian for the system and derive the discrete Stokes equations via the variational principle. This approach results in a stable, structure-preserving variational integrator that solves the system on general manifolds. △ Less

Submitted 13 January, 2025; v1 submitted 19 July, 2024; originally announced July 2024.

Journal ref: J. Fluid Mech. 1003 (2025) R1

Study of the decay and production properties of $D_{s1}(2536)$ and $D_{s2}^*(2573)$

Authors: M. Ablikim, M. N. Achasov, P. Adlarson, O. Afedulidis, X. C. Ai, R. Aliberti, A. Amoroso, Q. An, Y. Bai, O. Bakina, I. Balossino, Y. Ban, H. -R. Bao, V. Batozskaya, K. Begzsuren, N. Berger, M. Berlowski, M. Bertani, D. Bettoni, F. Bianchi, E. Bianco, A. Bortone, I. Boyko, R. A. Briere, A. Brueggemann , et al. (645 additional authors not shown)

Abstract: The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ processes are studied using data samples collected with the BESIII detector at center-of-mass energies from 4.530 to 4.946~GeV. The absolute branching fractions of $D_{s1}(2536)^- \rightarrow \bar{D}^{*0}K^-$ and $D_{s2}^*(2573)^- \rightarrow \bar{D}^0K^-$ are measured for the first time to be… ▽ More The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ processes are studied using data samples collected with the BESIII detector at center-of-mass energies from 4.530 to 4.946~GeV. The absolute branching fractions of $D_{s1}(2536)^- \rightarrow \bar{D}^{*0}K^-$ and $D_{s2}^*(2573)^- \rightarrow \bar{D}^0K^-$ are measured for the first time to be $(35.9\pm 4.8\pm 3.5)\%$ and $(37.4\pm 3.1\pm 4.6)\%$, respectively. The measurements are in tension with predictions based on the assumption that the $D_{s1}(2536)$ and $D_{s2}^*(2573)$ are dominated by a bare $c\bar{s}$ component. The $e^+e^-\rightarrow D_s^+D_{s1}(2536)^-$ and $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ cross sections are measured, and a resonant structure at around 4.6~GeV with a width of 50~MeV is observed for the first time with a statistical significance of $15σ$ in the $e^+e^-\rightarrow D_s^+D^*_{s2}(2573)^-$ process. It could be the $Y(4626)$ found by the Belle collaboration in the $D_s^+D_{s1}(2536)^{-}$ final state, since they have similar masses and widths. There is also evidence for a structure at around 4.75~GeV in both processes. △ Less

Submitted 10 July, 2024; originally announced July 2024.

Data quality control system and long-term performance monitor of the LHAASO-KM2A

Authors: Zhen Cao, F. Aharonian, Axikegu, Y. X. Bai, Y. W. Bao, D. Bastieri, X. J. Bi, Y. J. Bi, W. Bian, A. V. Bukevich, Q. Cao, W. Y. Cao, Zhe Cao, J. Chang, J. F. Chang, A. M. Chen, E. S. Chen, H. X. Chen, Liang Chen, Lin Chen, Long Chen, M. J. Chen, M. L. Chen, Q. H. Chen, S. Chen , et al. (263 additional authors not shown)

Abstract: The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic ray and gamma-ray showers. This information is used for physical analysis in gamma-ray astronomy and cosmic ray physics. To… ▽ More The KM2A is the largest sub-array of the Large High Altitude Air Shower Observatory (LHAASO). It consists of 5216 electromagnetic particle detectors (EDs) and 1188 muon detectors (MDs). The data recorded by the EDs and MDs are used to reconstruct primary information of cosmic ray and gamma-ray showers. This information is used for physical analysis in gamma-ray astronomy and cosmic ray physics. To ensure the reliability of the LHAASO-KM2A data, a three-level quality control system has been established. It is used to monitor the status of detector units, stability of reconstructed parameters and the performance of the array based on observations of the Crab Nebula and Moon shadow. This paper will introduce the control system and its application on the LHAASO-KM2A data collected from August 2021 to July 2023. During this period, the pointing and angular resolution of the array were stable. From the observations of the Moon shadow and Crab Nebula, the results achieved using the two methods are consistent with each other. According to the observation of the Crab Nebula at energies from 25 TeV to 100 TeV, the time averaged pointing errors are estimated to be $-0.003^{\circ} \pm 0.005^{\circ}$ and $0.001^{\circ} \pm 0.006^{\circ}$ in the R.A. and Dec directions, respectively. △ Less

Submitted 13 June, 2024; v1 submitted 20 May, 2024; originally announced May 2024.

Comments: 15 pages, 9 figures

Knowledge Gaps and Research Needs for Modeling CO2 Mineralization in the Basalt-CO2-Water System: A Review of Laboratory Experiments

Authors: Peng Lu, John Apps, Guanru Zhang, Alexander Gysi Chen Zhu

Abstract: Carbon capture and storage in basalt is being actively investigated as a scalable climate change mitigation option. Accurate geochemical modeling prediction of the extent and rate of CO2 mineralization is a critical component in assessing the local and global feasibility and efficacy of this strategy. In this study, we review basalt-CO2-water interaction experimental studies conducted during the l… ▽ More Carbon capture and storage in basalt is being actively investigated as a scalable climate change mitigation option. Accurate geochemical modeling prediction of the extent and rate of CO2 mineralization is a critical component in assessing the local and global feasibility and efficacy of this strategy. In this study, we review basalt-CO2-water interaction experimental studies conducted during the last two decades to determine whether they provide useable information for geochemical modeling. Most of the cited experiments generate data on the temporal evolution of water composition, and a few provide identification of secondary precipitates and their compositions, offering empirical and semi-quantitative information about the reactivity of basalts and the likelihood of secondary carbonate mineralization at various temperatures, pHs, and pCO2 conditions. However, most experiments provide insufficient information on the properties and quantity of secondary minerals formed, prohibiting accurate mass balance calculations and hence more quantitative geochemical modeling studies. Primary Ca, Mg, and Fe-bearing minerals in basalt control the availability of major ions released into aqueous solution for carbonate precipitation, and many secondary minerals, i.e., smectites, Ca-Mg-Fe carbonates, and zeolites, provide sinks for the same major ions, some of which are difficult to quantify experimentally. Thus, we have a multi-source and multi-sink inverse mass balance problem with insufficient constraints on the bulk system in which the temporal evolution of major ions does not provide sufficient information on which mineral(s) dissolve or the sequence of dissolution and precipitation reactions. Going forward, we propose that future experimental work should focus on trace elements and multiple isotopic tracers and better characterize the solid reaction products with modern analytical instruments. △ Less

Submitted 8 May, 2024; originally announced May 2024.

Linear correlations of Gibbs free energy for rare earth element oxide, hydroxide, chloride, fluoride, carbonate, and ferrite minerals and crystalline solids

Authors: Ruiguang Pan, Chen Zhu

Abstract: Rare Earth Elements (REE) are critical minerals (metals) for the transition from fossil fuels to renewable and clean energy. Accurate thermodynamic properties of REE minerals and other crystalline solids are crucial for geochemical modeling of the solubility, speciation, and transport of REE in ore formation, extraction, chemical processing, and recycling processes. However, the Gibbs free energie… ▽ More Rare Earth Elements (REE) are critical minerals (metals) for the transition from fossil fuels to renewable and clean energy. Accurate thermodynamic properties of REE minerals and other crystalline solids are crucial for geochemical modeling of the solubility, speciation, and transport of REE in ore formation, extraction, chemical processing, and recycling processes. However, the Gibbs free energies of formation (DGof, REEX) for these solids from different sources vary by 10s kJ/mol. We applied the Sverjensky linear free energy relationship (LFER) to evaluate their internal consistency and predict the unavailable DGof of the REE solids. By considering both the effects of ionic radius size and corresponding aqueous ion properties, the Sverjensky LFER allows estimates with much accuracy and precision. Here, rREEZ+ represents the Shannon-Prewitt ionic radii of REEZ+, and DGon, REEZ+ denotes the non-solvation contribution to the DGof of the aqueous REEZ+ ion. X represents the remainder of the compounds. In this study, the parameters aREEX, bREEX, and beta REEX were regressed from DGof compilations in the literature for 13 isostructural families. Based on these linear relationships, we recommend a set of internally consistent DGof, REEX for 119 end-members of REE oxides, hydroxides, chlorides, fluorides, carbonates, hydrous carbonates, and ferrites. These DGof, REEX are combined with experimental or predicted values of So, Vo, and Cpo from the literature and incorporated into a new SUPCRT database, which allows the calculations of thermodynamic properties to high P-T conditions (e.g., up to 1000 oC and 5 kb). △ Less

Submitted 6 May, 2024; originally announced May 2024.

Circularly Polarized Luminescence Without External Magnetic Fields from Individual CsPbBr3 Perovskite Quantum Dots

Authors: Virginia Oddi, Chenglian Zhu, Michael A. Becker, Yesim Sahin, Dmitry N. Dirin, Taehee Kim, Rainer F. Mahrt, Jacky Even, Gabriele Rainò, Maksym V. Kovalenko, Thilo Stöferle

Abstract: Lead halide perovskite quantum dots (QDs), the latest generation of colloidal QD family, exhibit outstanding optical properties which are now exploited as both classical and quantum light sources. Most of their rather exceptional properties are related to the peculiar exciton fine-structure of band-edge states which can support unique bright triplet excitons. The degeneracy of the bright triplet e… ▽ More Lead halide perovskite quantum dots (QDs), the latest generation of colloidal QD family, exhibit outstanding optical properties which are now exploited as both classical and quantum light sources. Most of their rather exceptional properties are related to the peculiar exciton fine-structure of band-edge states which can support unique bright triplet excitons. The degeneracy of the bright triplet excitons is lifted with energetic splitting in the order of millielectronvolts, which can be resolved by the photoluminescence (PL) measurements of single QDs at cryogenic temperatures. Each bright exciton fine-structure-state (FSS) exhibits a dominantly linear polarization, in line with several theoretical models based on the sole crystal field, exchange interaction and shape anisotropy. Here, we show that in addition to a high degree of linear polarization, the individual exciton FSS can exhibit a non-negligible degree of circular polarization even without external magnetic fields by investigating the four Stokes parameters of the exciton fine-structure in individual CsPbBr3 QDs through Stokes polarimetric measurements. We observe a degree of circular polarization up to ~38%, which could not be detected by using the conventional polarimetric technique. In addition, we found a consistent transition from left- to right-hand circular polarization within the fine-structure triplet manifold, which was observed in magnetic field dependent experiments. Our optical investigation provides deeper insights into the nature of the exciton fine-structures and thereby drives the yet-incomplete understanding of the unique photophysical properties of this novel class of QDs, potentially opening new scenarios in chiral quantum optics. △ Less

Submitted 2 April, 2024; originally announced April 2024.

Journal ref: ACS Nano 18, 17218 (2024)

Measurement of nonequilibrium vortex propagation dynamics in a nonlinear medium

Authors: Patrick C. Ford, Andrew A. Voitiv, Chuanzhou Zhu, Mark T. Lusk, Mark E. Siemens

Abstract: We observe and measure the nonequilibrium dynamics of optical vortices as a function of propagation distance through a nonlinear medium. The precession of a tilted-core vortex is quantified as is vortex-core sharpening, where the infinite width of a linear core subsequently shrinks and approaches the healing length of this nonlinear optical fluid. Experiments are performed with a variable-length n… ▽ More We observe and measure the nonequilibrium dynamics of optical vortices as a function of propagation distance through a nonlinear medium. The precession of a tilted-core vortex is quantified as is vortex-core sharpening, where the infinite width of a linear core subsequently shrinks and approaches the healing length of this nonlinear optical fluid. Experiments are performed with a variable-length nonlinear medium: a nonlinear fluid in a tank with an output window on a translating tube. This provides control over the distance the light propagates in the fluid and allows for the measurement of the dynamics throughout the entire propagation range. Results are compared to the predictions of a computational simulator to find the equivalent dimensionless nonlinear coefficient. △ Less

Submitted 29 March, 2024; originally announced April 2024.

Comments: 11 pages, 9 figures

Journal ref: Physics of Fluids 1 March 2024; 36 (3): 034128

Effects of Magnetic Helicity on 3D Equilibria and Self-Organized States in KTX Reversed Field Pinch

Authors: Ke Liu, Guodong Yu, Yuhua Huang, Wenzhe Mao, Yidong Xie, Xianyi Nie, Hong Li, Tao Lan, Jinlin Xie, Weixing Ding, Wandong Liu, Ge Zhuang, Caoxiang Zhu

Abstract: The RFP is a toroidal magnetic configuration in which plasmas can spontaneously transform into different self-organized states. Among various states, the QSH state has a dominant component for the magnetic field and significantly improves confinement. Many theoretical and experimental efforts have investigated the transitions among different states. This paper employs the MRxMHD model to study the… ▽ More The RFP is a toroidal magnetic configuration in which plasmas can spontaneously transform into different self-organized states. Among various states, the QSH state has a dominant component for the magnetic field and significantly improves confinement. Many theoretical and experimental efforts have investigated the transitions among different states. This paper employs the MRxMHD model to study the properties of QSH and other states. The SPEC is used to compute MHD equilibria for the KTX. The toroidal volume of KTX is partitioned into two subvolumes by an internal transport barrier. The geometry of this barrier is adjusted to achieve force balance across the interface, ensuring that the plasma in each subvolume is force-free and that magnetic helicity is conserved. By varying the parameters, we generate distinct self-organized states in KTX. Our findings highlight the crucial role of magnetic helicity in shaping these states. In states with low magnetic helicity in both subvolumes, the plasma exhibits axisymmetric behavior. With increasing core helicity, the plasma gradually transforms from an axisymmetric state to a double-axis helical state and finally to a single-helical-axis state. Elevated core magnetic helicity leads to a more pronounced dominant mode of the boundary magnetic field and a reduced core magnetic shear. This is consistent with previous experimental and numerical results in other RFP devices. We find a linear relationship between the plasma current and helicity in different self-organized states. Our findings suggest that KTX may enter the QSH state when the toroidal current reaches 0.72 MA. This study demonstrates that the stellarator equilibrium code SPEC unveils crucial RFP equilibrium properties, rendering it applicable to a broad range of RFP devices and other toroidal configurations. △ Less

Submitted 6 April, 2024; v1 submitted 25 January, 2024; originally announced January 2024.

Quasi-single-stage optimization for permanent magnet stellarators

Authors: Guodong Yu, Ke Liu, Tianyi Qian, Yidong Xie, Xianyi Nie, Caoxiang Zhu

Abstract: Advanced stellarators are typically optimized in two stages. The plasma equilibrium is optimized first, followed by the design of coils/permanent magnets. However, the coils/permanent magnets in the second stage may become too complex to achieve the desired equilibrium. To address this problem, a quasi-single-stage optimization method has been proposed. In this paper, we introduce this method for… ▽ More Advanced stellarators are typically optimized in two stages. The plasma equilibrium is optimized first, followed by the design of coils/permanent magnets. However, the coils/permanent magnets in the second stage may become too complex to achieve the desired equilibrium. To address this problem, a quasi-single-stage optimization method has been proposed. In this paper, we introduce this method for designing permanent magnet (PM) stellarators. The new approach combines straightforward PM metrics to penalize the maximum required PM thickness and the mismatch between the fixed-boundary equilibrium and the free-boundary one, along with typical physical targets. Since the degrees of freedom of the PMs are not included and directly used to minimize the objective function in this method, so we call it "quasi-single-stage" optimization. We apply this quasi-single-stage optimization method to find a new quasi-axisymmetric PM design. The new design starts from MUSE, which was initially designed using a two-stage optimization approach. The resulting design, MUSE++, exhibits an order of magnitude lower quasi-symmetric error and a one-order reduction in normal field error. We show that MUSE++ has approximately 30% fewer magnets compared to a proxy model "MUSE-0" that uses the same FAMUS optimization without the benefit of a single-stage equilibrium optimization. These results demonstrate that the new single-stage optimization method can concurrently improve plasma properties and simplify permanent magnet complexity. △ Less

Submitted 30 April, 2024; v1 submitted 25 January, 2024; originally announced January 2024.

Comments: 21 pages, 17 figures

Population inversion and ultrafast terahertz nonlinearity of transient Dirac fermions in Cd$_3$As$_2$

Authors: Changqing Zhu, Patrick Pilch, Renato M. A. Dantas, Anneke Reinold, Yunkun Yang, Faxian Xiu, Amilcar Bedoya-Pinto, Stuart S. P. Parkin, Roderich Moessner, Zhe Wang

Abstract: Harmonic generation provides an efficient tool for the study of ultrafast nonlinear dynamics. We report on time-resolved optical-pump terahertz-harmonic-generation spectroscopic investigation of ultrafast nonlinearity in a prototypical three-dimensional Dirac semimetal Cd$_3$As$_2$. A transient population inversion characterized by excessive nonthermal Dirac electrons and holes is found to be very… ▽ More Harmonic generation provides an efficient tool for the study of ultrafast nonlinear dynamics. We report on time-resolved optical-pump terahertz-harmonic-generation spectroscopic investigation of ultrafast nonlinearity in a prototypical three-dimensional Dirac semimetal Cd$_3$As$_2$. A transient population inversion characterized by excessive nonthermal Dirac electrons and holes is found to be very sensitive and responsive to a periodic terahertz drive, leading to very efficient terahertz third-harmonic generation. Based on the Boltzmann transport theory, we analyze the terahertz field-driven kinetics of the transient Dirac fermions that is responsible for the observed strong terahertz nonlinearity. △ Less

Submitted 16 January, 2024; originally announced January 2024.

Comments: 6 pages, 4 figures

Journal ref: Phys. Rev. B 109, L201111 (2024)

Analytic solution for pulse wave propagation in flexible tubes with application to patient-specific arterial tree

Authors: Peishuo Wu, Chi Zhu

Abstract: In this paper, we present an analytic solution for pulse wave propagation in a flexible arterial model with tapering, physiological boundary conditions and variable wall properties (wall elasticity and thickness). The change of wall properties follows a profile that is proportional to $r^α$, where $r$ represents the lumen radius and $α$ is a material coefficient. The cross-sectionally averaged vel… ▽ More In this paper, we present an analytic solution for pulse wave propagation in a flexible arterial model with tapering, physiological boundary conditions and variable wall properties (wall elasticity and thickness). The change of wall properties follows a profile that is proportional to $r^α$, where $r$ represents the lumen radius and $α$ is a material coefficient. The cross-sectionally averaged velocity and pressure are obtained by solving a hyperbolic system derived from the mass and momentum conservations, and they are expressed in Bessel functions of order $(4-α)/(3-α)$ and $1/(3-α)$, respectively. The solution is successfully validated by comparing it with numerical results from 3D fluid-structure interaction simulations. Subsequently, the solution is employed to study pulse wave propagation in an arterial model, revealing that the wall properties and the physiological outlet boundary conditions, such as the RCR model, play a crucial role in characterizing the input impedance and reflection coefficient. At low-frequency range, the input impedance is found to be insensitive to the wall properties and is primarily determined by the RCR parameters. At high-frequency range, the input impedance oscillates around the local characteristic impedance, and the oscillation amplitude varies non-monotonically with $α$. Expressions for the input impedance at both low-frequency and high-frequency limits are presented. This analytic solution is also successfully applied to model flow inside a patient-specific arterial tree, with the maximum relative errors in pressure and flow rate never exceeding $1.6\%$ and $9.0\%$ when compared to results from 3D numerical simulation. △ Less

Submitted 24 November, 2023; originally announced November 2023.

Journal ref: Journal of Fluid Mechanics. 2023;977:A36

A Design of Hadronic Calorimeter for DarkSHINE Experiment

Authors: Zhen Wang, Rui Yuan, Hanqing Liu, Xiang Chen, Shu Li, Kun Liu, Qibin Liu, Siyuan Song, Tong Sun, Yufeng Wang, Haijun Yang, Junhua Zhang, Yulei Zhang, Zhiyu Zhao, Chunxiang Zhu, Xuliang Zhu, Yifan Zhu

Abstract: The sensitivity of the dark photon search through invisible decay final states in low background experiments significantly relies on the neutron and muon veto efficiency, which depends on the amount of material used and the design of detector geometry. This paper presents an optimized design of a hadronic calorimeter (HCAL) used for the DarkSHINE experiment, which is studied using a GEANT4-based s… ▽ More The sensitivity of the dark photon search through invisible decay final states in low background experiments significantly relies on the neutron and muon veto efficiency, which depends on the amount of material used and the design of detector geometry. This paper presents an optimized design of a hadronic calorimeter (HCAL) used for the DarkSHINE experiment, which is studied using a GEANT4-based simulation framework. The geometry is optimized by comparing a traditional design with uniform absorbers to one that uses different thicknesses at different locations of the detector, which enhances the efficiency of vetoing low-energy neutrons at the sub-GeV level. The overall size and total amount of material used in HCAL are optimized to be lower due to the load and budget requirements, while the overall performance is studied to meet the physical objectives. △ Less

Submitted 4 September, 2024; v1 submitted 3 November, 2023; originally announced November 2023.

Comments: 12 pages, 9 figures

High-speed photon correlation monitoring of amplified quantum noise by chaos using deep-learning balanced homodyne detection

Authors: Yanqiang Guo, Zinan Hu, Jianchao Zhang, Chenyu Zhu, Xiaomin Guo

Abstract: Precision experimental determination of photon correlation requires the massive amounts of data and extensive measurement time. We present a technique to monitor second-order photon correlation $g^{(2)}(0)$ of amplified quantum noise based on wideband balanced homodyne detection and deep-learning acceleration. The quantum noise is effectively amplified by an injection of weak chaotic laser and the… ▽ More Precision experimental determination of photon correlation requires the massive amounts of data and extensive measurement time. We present a technique to monitor second-order photon correlation $g^{(2)}(0)$ of amplified quantum noise based on wideband balanced homodyne detection and deep-learning acceleration. The quantum noise is effectively amplified by an injection of weak chaotic laser and the $g^{(2)}(0)$ of the amplified quantum noise is measured with a real-time sample rate of 1.4 GHz. We also exploit a photon correlation convolutional neural network accelerating correlation data using a few quadrature fluctuations to perform a parallel processing of the $g^{(2)}(0)$ for various chaos injection intensities and effective bandwidths. The deep-learning method accelerates the $g^{(2)}(0)$ experimental acquisition with a high accuracy, estimating 6107 sets of photon correlation data with a mean square error of 0.002 in 22 seconds and achieving a three orders of magnitude acceleration in data acquisition time. This technique contributes to a high-speed and precision coherence evaluation of entropy source in secure communication and quantum imaging. △ Less

Submitted 14 July, 2023; v1 submitted 6 July, 2023; originally announced July 2023.

Comments: 6 pages, 6 figures