Showing 1–50 of 241 results for author: Shi, B

Observation of node-dependent Rydberg molecular bound states

Authors: Qing Li, Shi-Yao Shao, Jun Zhang, Han-Chao Chen, Li-Hua Zhang, Bang Liu, Guang-Can Guo, Dong-Sheng Ding, Bao-Sen Shi

Abstract: Ultralong-range Rydberg molecules, formed by the interaction between a highly excited Rydberg atom and a ground-state atom, provide a unique platform for exploring quantum phenomena spanning nanometer-to-micrometer distances as well as exotic few-body interactions. The formation mechanisms and resultant physical properties differ markedly between s-wave and p-wave scattering channels. Here we repo… ▽ More Ultralong-range Rydberg molecules, formed by the interaction between a highly excited Rydberg atom and a ground-state atom, provide a unique platform for exploring quantum phenomena spanning nanometer-to-micrometer distances as well as exotic few-body interactions. The formation mechanisms and resultant physical properties differ markedly between s-wave and p-wave scattering channels. Here we report the experimental observation of node-dependent p-wave molecular signals in Rb(nS)-Rb(5S) Rydberg molecular spectra, where variations in the principal quantum number n directly reveal the shift of molecular binding energies induced by the moving nodal structure of the Rydberg electron wavefunction. This node-dependence is attributed to a cooperative effect between the local gradient of the nS-electron wavefunction and the energydependent p-wave scattering length. In addition, resolving two p-wave bound states associated with adjacent nodes highlights the remarkable sub-nanometer spatial resolution achieved in our experiment. Our findings reveal a more profound quantum control mechanism, wherein the principal quantum number acts as a switch for nodal-selective molecular bound states, and the reported method provides a sensitive spectroscopic probe of electron-atom scattering. △ Less

Submitted 9 July, 2026; originally announced August 2026.

The Most Dangerous Seed: Nonlinear Optimal Perturbations in Rayleigh-Taylor Instability

Authors: Suoqing Ji, Bin Shi

Abstract: Long-term instabilities in astrophysical fluids are inherently nonlinear, where even small-amplitude perturbations can trigger dramatic instability. However, owing to the complex interactions among non-normal modes, the perturbation structures responsible for the greatest growth remain poorly understood. In this paper, we employ the nonlinear optimization method known as the conditional nonlinear… ▽ More Long-term instabilities in astrophysical fluids are inherently nonlinear, where even small-amplitude perturbations can trigger dramatic instability. However, owing to the complex interactions among non-normal modes, the perturbation structures responsible for the greatest growth remain poorly understood. In this paper, we employ the nonlinear optimization method known as the conditional nonlinear optimal perturbation (CNOP) to identify the most dangerous initial velocity perturbation, i.e., the perturbation that maximizes the kinetic energy growth in the two-dimensional compressible Rayleigh-Taylor instability in astrophysical hydrodynamics. Compared with random perturbations, the optimal perturbation forms a coherent wave-packet structure localized around the density interface. We investigate its dependence on spatial resolution and optimization time horizon through two sets of numerical experiments. For a fixed optimization time, increasing the spatial resolution produces a more sharply localized wave packet, whereas for a fixed spatial resolution, increasing the optimization time causes the wave packet to become progressively more dispersed. Furthermore, we analyze the optimal perturbations in Fourier space using the fast Fourier transform (FFT), which provides a clearer characterization of the spectral distribution. Higher-resolution simulations concentrate most of the perturbation energy into only a few dominant modes, while longer optimization times distribute the energy over a broader range of modes. These results indicate that short optimization time horizons involve relatively weak modal interactions and remain closer to the linear regime, whereas longer optimization times enhance nonlinear modal interactions, broaden the spectral distribution, and reduce the predictive capability of linear stability theory. △ Less

Submitted 4 August, 2026; originally announced August 2026.

Comments: 15 pages, 7 figures, submitted to ApJ

Dyna-Mat: End-to-end benchmarking of foundation machine learning interatomic potentials in finite-temperature ensembles

Authors: Mikołaj J. Gawkowski, Nongnuch Artrith, Silvia Bonfanti, Abhijeet Sadashiv Gangan, Hendrik H. Heenen, Joseph Kioseoglou, Ivor Lončarić, Hemanadhan Myneni, Janosh Riebesell, Mariana Rossi, Matthias Rupp, Jonathan Schmidt, Shubham Sharma, Benjamin X. Shi, Antoni Wadowski, Lukas Hörmann, Venkat Kapil

Abstract: Foundation machine learning interatomic potentials (MLIPs) are increasingly being used as drop-in replacements for first-principles calculations, enabling simulations of materials at length and time scales that were previously inaccessible. However, due to lack of ground truth data, their accuracy on structural and dynamical observables in finite thermodynamic ensembles is yet to be established. H… ▽ More Foundation machine learning interatomic potentials (MLIPs) are increasingly being used as drop-in replacements for first-principles calculations, enabling simulations of materials at length and time scales that were previously inaccessible. However, due to lack of ground truth data, their accuracy on structural and dynamical observables in finite thermodynamic ensembles is yet to be established. Here, we introduce Dyna-Mat-v1.0, a benchmark dataset of condensed-phase first-principles molecular dynamics trajectories designed to test foundation MLIPs at realistic finite-temperature conditions. Using this dataset, we evaluate 15 foundation MLIPs across four model tiers by comparing both single-point energy and force errors on first-principles configurations and observables generated from MLIP-driven trajectories. We find that "on average" models with lower single-point force errors also yield lower errors for structural and dynamical observables. However, there are individual systems for which low force errors lead to qualitative failures in the predicted structure. Pressure remains poorly described across most models, pointing to limitations in the density functional theory stress labels available in current large-scale training datasets. Finally, we construct an accuracy-cost Pareto frontier to identify the best trade-offs for molecular dynamics with foundation MLIPs, finding that the latest generation of cross-trained models is close to Pareto-optimal according to the accuracy metrics considered here. Overall, Dyna-Mat-v1.0 shows that end-to-end finite-temperature validation is essential for quantifying the predictive behaviour of foundation MLIPs, and provides a simple, scalable route for assessing them beyond static and harmonic benchmarks relevant to materials design. △ Less

Submitted 3 July, 2026; originally announced July 2026.

Comments: 40 pages, 16 figures, includes Supporting Information

Material-Anisotropy-Driven Topological Optical Lattices on Thin-Film Lithium Niobate

Authors: Siyuan Zhang, Baoqi Shi, Lei Gui, Xiangle Li, Junna Yao, Zhaosheng Chu, Jun Xu, Qiwen Zhan, Junqiu Liu, Anting Wang

Abstract: Integrated structured-light sources usually obtain high-dimensional orbital angular momentum (OAM) states by encoding each channel into separate gratings, waveguides or metasurfaces, which ties modal capacity to structural complexity. Here we show that intrinsic material anisotropy can instead act as a built-in angular-momentum coupler. In an X-cut thin-film lithium niobate (TFLN) microring vortex… ▽ More Integrated structured-light sources usually obtain high-dimensional orbital angular momentum (OAM) states by encoding each channel into separate gratings, waveguides or metasurfaces, which ties modal capacity to structural complexity. Here we show that intrinsic material anisotropy can instead act as a built-in angular-momentum coupler. In an X-cut thin-film lithium niobate (TFLN) microring vortex emitter, the in-plane optical axis causes a circulating whispering-gallery mode to sample a periodically varying effective index, producing continuous azimuthal phase modulation. This modulation converts each resonance from a nominal single-charge emitter into a coherent topological sideband lattice with charges l=l_p+2n and Bessel-weighted amplitudes. Broadband measurements resolve a representative principal-charge series from l_p=-13 to +13, while additional devices with 100 and 200 GHz free spectral ranges (FSRs) show scalable resonance addressability. The emitted lattices are reproduced by a forward-calculated Fourier--Bessel model, supported by OAM projection measurements, and exhibit focusing into annular perfect-vortex fields and self-healing after obstruction. Waveguide-induced circular polarization further adds a vectorial spin--orbit channel. These results turn TFLN anisotropy from a material constraint into a compact mechanism for resonance-addressed high-dimensional structured-light generation. △ Less

Submitted 21 June, 2026; originally announced June 2026.

Controlling the phase behaviour of ultraconfined water via bilayer graphene stacking

Authors: Yixuan Pu, Benjamin X. Shi, Pavan Ravindra, Chris Pickard, Angelos Michaelides, Venkat Kapil

Abstract: Water confined within nanoscale capillaries exhibits phase behaviour and transport properties that differ substantially from bulk, and these effects are commonly interpreted as consequences of geometric confinement and reduced dimensionality. Here we show that confinement topology alone is insufficient to predict the behaviour of nanoconfined water. Using machine learning interatomic potentials wi… ▽ More Water confined within nanoscale capillaries exhibits phase behaviour and transport properties that differ substantially from bulk, and these effects are commonly interpreted as consequences of geometric confinement and reduced dimensionality. Here we show that confinement topology alone is insufficient to predict the behaviour of nanoconfined water. Using machine learning interatomic potentials with first-principles accuracy, we compute the density-temperature phase diagram of water confined within bilayer graphene nanocapillaries and compare AA and AB stacking arrangements, which differ only by a lateral shift of 1.4 Å. Despite this minimal structural change, AA stacking can stabilise different ice polymorphs, can increase the melting temperature by more than 100 K, can enhance proton transfer, and alters the onset of superionic behaviour relative to AB stacking. We trace these effects to stacking-induced changes in the hydrogen-bond network associated with modifications to the lateral free energy landscape and neighbouring O-O separations. Our results demonstrate that even subtle atomistic variations in the confining walls can qualitatively reshape the physical and chemical behaviour of nanoconfined water, with implications for the interpretation and control of fluids under angstrom-scale confinement. △ Less

Submitted 19 June, 2026; originally announced June 2026.

Comments: 28 pages, 4 figures

Tripartite entanglement of remote atomic qubits

Authors: Isabella Goetting, Ashish Kalakuntla, Mikhail Shalaev, Harriet Bufan Shi, Ana Ferrari, Sagnik Saha, George Toh, Saki Male, Christopher Monroe

Abstract: Distributed entanglement across multi-node quantum networks is essential for a wide range of quantum technologies, including modular quantum computers, distributed sensing and metrology, and multi-party secure communication protocols. Such large-scale quantum networks will require photonic interconnects to generate and sustain entangled states across localized nodes. Previously, three-node distrib… ▽ More Distributed entanglement across multi-node quantum networks is essential for a wide range of quantum technologies, including modular quantum computers, distributed sensing and metrology, and multi-party secure communication protocols. Such large-scale quantum networks will require photonic interconnects to generate and sustain entangled states across localized nodes. Previously, three-node distributed Greenberger-Horne-Zeilinger (GHZ) states have been generated between solid-state qubits and atomic ensembles, but not yet in the platform of individual atomic qubits, which can be replicated, detected, and individually controlled with high fidelity. Here we report the first fully-distributed GHZ state of qubits across a three-node quantum network of single atomic memories, using photonic interconnects. We achieve a bounded fidelity of $0.841(17) \leq \mathcal{F} \leq 0.881(17)$ at an entanglement generation rate of 0.095(5)/sec and measure a clear violation of Mermin's inequality while closing the detection loophole for the first time in a fully-distributed multipartite entangled state. △ Less

Submitted 15 June, 2026; originally announced June 2026.

Comments: 12 pages, 8 figures

Ultra-broadband Anti-Jamming Communication via a Rydberg Atomic Receiver

Authors: Jia-Dou Nan, Jun-Rong Chen, Bang Liu, Qi-Feng Wang, Yu Ma, Yi-Ming Yin, Tian-Yu Han, Guang-Can Guo, Hao Tian, Li-Hua Zhang, Bo Du, Bin-Bin Wei, Dong-Sheng Ding, Bao-Sen Shi

Abstract: Ultra-broadband anti-jamming communication represents a promising approach to secure and robust information transfer through spread-spectrum techniques, effectively combatting malicious interference and eavesdropping. Rydberg atoms, enhanced by waveguide coupling, facilitate ultra-broadband spectrum sensing without traditional RF components. This framework provides an experimental platform for ult… ▽ More Ultra-broadband anti-jamming communication represents a promising approach to secure and robust information transfer through spread-spectrum techniques, effectively combatting malicious interference and eavesdropping. Rydberg atoms, enhanced by waveguide coupling, facilitate ultra-broadband spectrum sensing without traditional RF components. This framework provides an experimental platform for ultra-wide anti-jamming communication. Here, we demonstrate real-time signal demodulation based on frequency-hopping spread spectrum (FHSS) in a waveguide-coupled Rydberg receiver, achieving ultra-broad frequency-hopping covering 100 kHz to 20 GHz and a hopping rate of 100 khop/s. When confined to a standard operational band (e.g., the 2.4 GHz ISM band), our system achieves a high channel density of 8 channels per MHz. Beyond this, by leveraging its ultra-broad and continuous bandwidth, the system supports over 150,000 channels. Experimental results reveal a 51 dB enhancement in narrowband interference tolerance compared with single-frequency systems, confirming its outstanding anti-jamming capability. The reported system demonstrates significant potential for secure communications based on quantum technology, especially communication in complex electromagnetic environments. △ Less

Submitted 12 June, 2026; originally announced June 2026.

Length-dependent SWIR upconversion spectral response of noncritically phase-matched KTP crystals

Authors: Xiao-Hua Wang, Chang-Hao Min, Yin-Hai Li, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Noncritically phase-matched (NCPM) KTP crystals support large-aperture bulk operation, avoid spatial walk-off, and relax angular-alignment requirements, making them attractive for short-wave infrared upconversion detection. To guide crystal selection for different detection requirements, we quantitatively characterize how crystal length affects the coverage and profile of their external upconversi… ▽ More Noncritically phase-matched (NCPM) KTP crystals support large-aperture bulk operation, avoid spatial walk-off, and relax angular-alignment requirements, making them attractive for short-wave infrared upconversion detection. To guide crystal selection for different detection requirements, we quantitatively characterize how crystal length affects the coverage and profile of their external upconversion spectral responses. A calibrated Czerny--Turner monochromator is used to measure the responses of 0.5, 1.0, and 2.0 mm crystals and compare them with theoretical quantum-efficiency spectra calculated from the phase-matching model. With increasing crystal length, the response evolves from a broad profile with weak peak separation to a more distinct double-peak structure, accompanied by reduced coverage bandwidth. A representative pump-power measurement further yields the system-level external quantum-efficiency slope. These results clarify the trade-off between spectral coverage and wavelength selectivity for different crystal lengths and can be used to choose the crystal length for SWIR upconversion detection systems. △ Less

Submitted 28 June, 2026; v1 submitted 9 June, 2026; originally announced June 2026.

Comments: 11 pages,5 figures

Distilling first-principles accuracy into compact machine learning potentials for condensed-phase chemistry

Authors: Sijia Chen, Niamh O'Neill, Benjamin X. Shi, Venkat Kapil

Abstract: Accurate machine learning interatomic potentials (MLIPs) have made first-principles-quality potential energy surfaces increasingly accessible for condensed-phase chemistry, but their inference cost can still limit the sampling needed to compute experimentally relevant observables. In this work, we combine transfer learning and knowledge distillation to construct compact "student" models that retai… ▽ More Accurate machine learning interatomic potentials (MLIPs) have made first-principles-quality potential energy surfaces increasingly accessible for condensed-phase chemistry, but their inference cost can still limit the sampling needed to compute experimentally relevant observables. In this work, we combine transfer learning and knowledge distillation to construct compact "student" models that retain the accuracy of much larger "teacher" models obtained by applying transfer learning to foundation models. The resulting students reduce production simulation cost by roughly an order of magnitude, making high-accuracy sampling practical for challenging condensed-phase problems. We demonstrate this across three problems of increasing sampling complexity: finite-temperature NPT simulations of ice Ih, classical and path-integral simulations of liquid water over 240-370 K, and path-integral umbrella-sampling simulations of water dissociation at the anatase TiO2(101)/water interface. In all cases, the distilled students reproduce the target observables of their teachers more reliably than models of the same size trained directly on the limited reference data. The liquid-water student, distilled from a Δ-learned CCSD(T)-quality teacher, reproduces thermodynamic, structural, transport, and nuclear quantum properties over the full temperature range studied. At the TiO2/water interface, distillation makes PIMD umbrella sampling practical and shows that nuclear quantum effects lower the dissociation barrier by roughly 2 kcal/mol and shift the molecular-dissociated free energy difference into quantitative agreement with recent solid-state 17O NMR measurements. Our work demonstrates how knowledge distillation can make accurate MLIPs practical for the sampling methods needed to connect condensed-phase reaction thermodynamics with experiment, notably for interfacial chemistry and catalysis. △ Less

Submitted 4 June, 2026; originally announced June 2026.

How reproducible are first-principles simulations of liquid water?

Authors: Niamh ONeill, Benjamin X. Shi, William J. Baldwin, Albert P. Bartok, Chris J. Pickard, Angelos Michaelides, Gabor Csanyi, Timothy C. Berkelbach

Abstract: Liquid water is fundamentally important, and its accurate computer simulation has been the driving force for myriad methodological developments. Ab initio molecular dynamics with forces obtained from density functional theory (DFT) is now a standard tool widely used by researchers. However, we reveal that previous studies of liquid water using the same widely-used density functional (revPBE-D3) ex… ▽ More Liquid water is fundamentally important, and its accurate computer simulation has been the driving force for myriad methodological developments. Ab initio molecular dynamics with forces obtained from density functional theory (DFT) is now a standard tool widely used by researchers. However, we reveal that previous studies of liquid water using the same widely-used density functional (revPBE-D3) exhibit significant discrepancies with one another, varying by over 20% in the diffusion coefficient and 10% in the density, raising fundamental questions about reproducibility. By combining modern long-range machine-learning interatomic potentials that enable robust statistical sampling with carefully converged DFT training data, we resolve these discrepancies, achieving consensus across six diverse community codes. Our predictions differ markedly from previous literature: we show that most previous results overestimate the density and underestimate the diffusion coefficient of revPBE-D3 water due to basis set incompleteness and pseudopotential inconsistencies, coupled with limitations in statistical sampling (in some cases). These benchmark values provide a reliable reference for validating current and future implementations of DFT-based ab initio molecular dynamics. Reaching agreement establishes confidence and credibility and serves as a prerequisite for the systematic assessment of new density functionals and numerical approximations. △ Less

Submitted 27 May, 2026; originally announced May 2026.

Diagrammatic Monte Carlo for Fermionic Rényi Entanglement Entropy

Authors: Boyuan Shi

Abstract: We develop a direct diagrammatic Monte Carlo framework for the Renyi entanglement entropy of interacting lattice fermions. The method starts from the fermionic graded-swap representation of Z_n[A]=Tr_Aρ_A^n, which converts the entropy problem into a replicated path integral with mixed temporal boundary conditions on the entangling region. In this representation the replica momenta are half-shifted… ▽ More We develop a direct diagrammatic Monte Carlo framework for the Renyi entanglement entropy of interacting lattice fermions. The method starts from the fermionic graded-swap representation of Z_n[A]=Tr_Aρ_A^n, which converts the entropy problem into a replicated path integral with mixed temporal boundary conditions on the entangling region. In this representation the replica momenta are half-shifted, q_m=(2m+1)π/n, and the interaction expansion has a determinant form suitable for connected-determinant summation. We combine this expansion with a many-configuration Markov-chain Monte Carlo sampler to obtain order-by-order corrections for very large systems to very high orders. As a benchmark, we compare the order-by-order coefficients of a 3*3 Hubbard cluster with exact diagonalization. We then report a production calculation for a large periodic lattice with a square subregions. The dominant system-size limitation is therefore memory rather than a conventional auxiliary-field sign problem. The results provide a step toward diagrammatic calculations of fermionic entanglement observables in regimes where direct quantum Monte Carlo sampling is costly or sign-problem limited. △ Less

Submitted 20 May, 2026; originally announced May 2026.

Comments: 5 pages, 1 figure

Assessing the impact of nodal surface optimization in fixed-node diffusion Monte Carlo on non-covalent interactions

Authors: Kousuke Nakano, Benjamin X. Shi, Dario Alfè, Andrea Zen

Abstract: Diffusion quantum Monte Carlo (DMC) and coupled cluster theory [CCSD(T)] are widely-employed benchmark methods for noncovalent interactions (NCIs). However, recent studies have reported notable discrepancies across several hydrogen-bonded and dispersion-dominated systems, raising questions on the accuracy of the approximations underlying each approach. In DMC, the dominant error is expected to ste… ▽ More Diffusion quantum Monte Carlo (DMC) and coupled cluster theory [CCSD(T)] are widely-employed benchmark methods for noncovalent interactions (NCIs). However, recent studies have reported notable discrepancies across several hydrogen-bonded and dispersion-dominated systems, raising questions on the accuracy of the approximations underlying each approach. In DMC, the dominant error is expected to stem from the fixed-node approximation, where the nodal surface is typically taken from a single Slater determinant derived from a density functional theory or Hartree-Fock calculation. In this work, we assess the impact of nodal surface optimization on DMC predictions for 12 compounds spanning diverse NCIs, using a recently proposed antisymmetrized geminal power ansatz with natural orbitals. We find improved agreement with CCSD(T) for hydrogen-bonded systems, while having negligible effect for dispersion-dominated systems. These results provide a practical and computationally efficient route to resolving discrepancies in hydrogen-bonded interactions, while offering insight into the remaining differences in dispersion-dominated systems. △ Less

Submitted 5 April, 2026; originally announced April 2026.

Comments: 12 pages, 2 figures

Enhanced electron injection for efficient proton acceleration and neutron production in femtosecond laser-driven nano-structured targets

Authors: Yingzi Dai, Chengyu Qin, Hui Zhang, Guoqiang Zhang, Changbo Fu, Xiangai Deng, Dirui Xu, Shuai Xu, Xuesong Geng, Jing Wang, Bowen Zhang, Yunwei Cui, Xiaojing Guo, Weifu Yin, Yanqi Liu, Xingyan Liu, Cheng Wang, Zongxin Zhang, Bingnan Shi, Lianghong Yu, Xiaoyan Liang, Yuxin Leng, Baifei Shen, Liangliang Ji, Ruxin Li

Abstract: Micro- or nano-structured targets are advantageous in enhancing and manipulating laser-proton acceleration, due to the increased absorption of laser energy and onset of direct laser acceleration for high-energy electrons. Here, we experimentally demonstrate that nano-wire-array printed on a flat substrate is an efficient nano-injector of relativistic electrons that leads to a significant boost of… ▽ More Micro- or nano-structured targets are advantageous in enhancing and manipulating laser-proton acceleration, due to the increased absorption of laser energy and onset of direct laser acceleration for high-energy electrons. Here, we experimentally demonstrate that nano-wire-array printed on a flat substrate is an efficient nano-injector of relativistic electrons that leads to a significant boost of laser-driven proton acceleration and neutron production beyond normal geometry. By employing an ultra-intense (2*1021 W/cm2) femtosecond laser pulse to irradiate nano-wire-array targets, protons with cut-off energies of 62.8 MeV are generated, and notably, the energy conversion efficiency from laser to protons reaches up to 9% - 3.5 times higher than that of flat foils. After bombarding a beryllium converter, 1.1*1010 neutrons are produced. Full 3D particle-in-cell simulations have reproduced experimental results and reveal interference mechanisms between the nano-wires and substrate, leading to continuous pumping of electrons from the substrate and standing-wave enhanced re-injection from the wire tip. This efficient injection finally results in the large sheath field and thus high yield of energetic protons and neutrons. Dependence on the wire length and scaling with laser amplitude are further discussed. These results suggest that 3D-printed structures are promising in developing compact laser-driven high-flux proton and neutron sources for numerous applications. △ Less

Submitted 3 April, 2026; originally announced April 2026.

Comments: 23 pages,6 figures

Kramers-Kronig causality in integrated photonics: The spectral tension between ultraviolet transition and mid-infrared absorption

Authors: Yue Hu, Zhenyuan Shang, Chenxi Zhang, Yuanjie Ning, Weiqin Zheng, Dengke Chen, Sanli Huang, Baoqi Shi, Zeying Zhong, Hao Tan, Wei Sun, Yi-Han Luo, Xinmao Yin, Zhi-Chuan Niu, Junqiu Liu

Abstract: Dispersion engineering via geometric confinement is essential to integrated photonics, enabling phenomena such as soliton microcombs, supercontinua, parametric oscillators, and entangled photons. However, prevailing methodologies rely on semi-empirical Sellmeier models that assume idealized material purity, neglecting the pronounced dispersion shifts induced by residual impurities like hydrogen-re… ▽ More Dispersion engineering via geometric confinement is essential to integrated photonics, enabling phenomena such as soliton microcombs, supercontinua, parametric oscillators, and entangled photons. However, prevailing methodologies rely on semi-empirical Sellmeier models that assume idealized material purity, neglecting the pronounced dispersion shifts induced by residual impurities like hydrogen-related bonds. Here, we demonstrate that these residual bonds fundamentally alter the dispersion landscape spanning from the ultraviolet (UV) to the mid-infrared (MIR) spectra. Specifically, they introduce MIR vibrational absorption while simultaneously modifying UV electronic transition, shifting the bandgap and UV pole. We show that the spectral tension between these UV and MIR modifications dictates the group velocity dispersion from the visible to the near-infrared (NIR) via the Kramers-Kronig causality. We experimentally validate this phenomenon through systematic characterization of broadband loss and dispersion in ultralow-loss silicon nitride photonic integrated circuits. By rigorously incorporating these effects, we bridge the gap between empirical fitting and predictive physical modelling. Our study resolves long-standing discrepancies in dispersion engineering, providing precision control essential for next-generation integrated photonics. △ Less

Submitted 31 March, 2026; v1 submitted 30 March, 2026; originally announced March 2026.

Comments: 11 pages, 5 figures

Enhancement of vacuum-ultraviolet dispersive-wave emission using gas-filled tapered hollow-core fibers

Authors: Yinuo Zhao, Donghan Liu, Baoqi Shi, Zhiyuan Huang, Tiandao Chen, Jinyu Pan, Zhengzheng Liu, Xinglin Zeng, Wenbin He, Jiapeng Huang, Jinxin Zhan, Xin Jiang, Yuxin Leng, Junqiu Liu, Meng Pang

Abstract: The recent breakthroughs in laser-driving 229Th nuclear transition have created an urgent demand for coherent vacuum-ultraviolet (VUV) sources delivering high spectral brightness at the critical 148.38 nm isomer energy. However, generating sufficient photon flux to overcome the low nuclear excitation probability remains a challenge for compact setups. While resonant dispersive wave emission in gas… ▽ More The recent breakthroughs in laser-driving 229Th nuclear transition have created an urgent demand for coherent vacuum-ultraviolet (VUV) sources delivering high spectral brightness at the critical 148.38 nm isomer energy. However, generating sufficient photon flux to overcome the low nuclear excitation probability remains a challenge for compact setups. While resonant dispersive wave emission in gas-filled hollow-core fibers offers a promising route, standard capillaries face a fundamental trade-off: maximizing input coupling requires large core diameters, whereas efficient nonlinear VUV conversion demands the high intensities using small cores. Here, we resolve this conflict using a gas-filled tapered capillary fiber. This architecture utilizes a longitudinally decreasing core diameter to combine a large input aperture with adiabatic field concentration, thereby continuously enhancing the nonlinear interaction. Experimentally, we demonstrate a widely tunable source (135-240 nm) that achieves a twofold efficiency enhancement specifically at the 148.38 nm wavelength compared to uniform geometries. By providing a scalable route to high-flux VUV generation, this work establishes a critical tabletop tool for advancing solid-state nuclear clocks and time-resolved spectroscopy. △ Less

Submitted 18 March, 2026; originally announced March 2026.

Experimental Determination of Gamma-Ray Polarization in Strong-Field Nonlinear Compton Scattering

Authors: Pengpei Xie, Mingyang Zhu, Xichen Hu, Yanfei Li, Yifei Li, Tianbing Wang, Bingjun Li, Huitong Zhai, Bingzhan Shi, Zewei Zhang, Ruiqi Qin, Jie Feng, Jinguang Wang, Xin Lu, Liming Chen, Yutong Li

Abstract: The polarization of gamma rays produced in strong-field quantum electrodynamics (SFQED) is a fundamental and long-standing prediction, the verification of which has remained elusive, limiting both foundational tests and applications. Here, we report the first experimental measurement of gamma-ray polarization generated via all-optical nonlinear Compton scattering. Colliding a laser-wakefield-accel… ▽ More The polarization of gamma rays produced in strong-field quantum electrodynamics (SFQED) is a fundamental and long-standing prediction, the verification of which has remained elusive, limiting both foundational tests and applications. Here, we report the first experimental measurement of gamma-ray polarization generated via all-optical nonlinear Compton scattering. Colliding a laser-wakefield-accelerated electron beam with an intense counter-propagating laser pulse reflected from a plasma mirror, we produce bright gamma rays in the strong-field regime ($a_0 > 1$). For gamma rays with $a_0 \approx 3$, a linear polarization degree of $\sim 50\%$ is measured via the azimuthal asymmetry of photoneutrons from a deuterium target, and independently verified by a Compton polarimeter.The results show excellent agreement with SFQED calculations employing the locally monochromatic approximation, while diverging from predictions based on the locally constant field approximation, highlighting the importance of quantum interference effects in this regime. Our work provides experimental evidence for polarization dynamics in SFQED, supports a key prediction of nonperturbative QED, and paves the way for compact, laser-driven sources of polarized gamma rays.} △ Less

Submitted 13 March, 2026; originally announced March 2026.

From Accurate Quantum Chemistry to Converged Thermodynamics for Ion Pairing in Solution

Authors: Niamh O'Neill, Benjamin X. Shi, William C. Witt, Blake I. Armstrong, William J. Baldwin, Paolo Raiteri, Christoph Schran, Angelos Michaelides, Julian D. Gale

Abstract: Quantitative prediction of thermodynamic properties in solution is essential for translating atomistic simulations into reliable chemical insight. As an exemplar system, the behaviour of CaCO$_3$ in water has been widely studied to understand its mineralization in seawater, with potential implications for carbon-capture strategies. However, making accurate computational predictions has been a long… ▽ More Quantitative prediction of thermodynamic properties in solution is essential for translating atomistic simulations into reliable chemical insight. As an exemplar system, the behaviour of CaCO$_3$ in water has been widely studied to understand its mineralization in seawater, with potential implications for carbon-capture strategies. However, making accurate computational predictions has been a long-standing challenge, requiring both highly accurate electronic structure methods and extensive statistical sampling. Here, we combine advances in machine learning and electronic structure theory to fully resolve the ion pairing free energy of CaCO$_3$ with explicit solvation. We show that achieving quantitative agreement with experiment requires going beyond the standard density functional theory up to the "gold-standard" coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)]. We generate a set of systematically improvable models, enabling reliable insights into the initial association mechanism of Ca and CO$_3$ ions prior to nucleation while fully quantifying enthalpic and entropic effects. Our results demonstrate that CCSD(T)-level thermodynamic predictions of complex aqueous systems can now be routinely achieved. △ Less

Submitted 6 March, 2026; originally announced March 2026.

Fingerprint Recognition of Partial Discharge Signals in Deep Learning Enhanced Rydberg Atomic Sensors

Authors: Yi-Ming Yin, Qi-Feng Wang, Yu Ma, Tian-Yu Han, Jia-Dou Nan, Zheng-Yuan Zhang, Han-Chao Chen, Xin Liu, Shi-Yao Shao, Jun Zhang, Qing Li, Ya-Jun Wang, Dong-Yang Zhu, Qiao-Qiao Fang, Chao Yu, Bang Liu, Li-Hua Zhang, Dong-Sheng Ding, Bao-Sen Shi

Abstract: Partial discharge originates from microscopic insulation imperfections in high-voltage apparatus and is widely considered a critical marker of incipient deterioration. Conventional partial discharge detection methods are typically constrained by limited bandwidth and often rely on predefined feature extraction, which impedes reliable recognition of broadband transient signals. In this work, we emp… ▽ More Partial discharge originates from microscopic insulation imperfections in high-voltage apparatus and is widely considered a critical marker of incipient deterioration. Conventional partial discharge detection methods are typically constrained by limited bandwidth and often rely on predefined feature extraction, which impedes reliable recognition of broadband transient signals. In this work, we employ a Rydberg atomic sensor to directly capture time-domain responses of partial discharge emissions and construct distinctive spectral fingerprints for different types. A 1D ResNet deep learning model is then applied to recognize these fingerprints from time-domain signals without manual feature engineering. Under increased source-antenna distances, where spectral features are significantly attenuated, the model attains a recognition accuracy of approximately 94\% across four partial discharge categories, demonstrating robustness to attenuation and noise. We further validate the approach in a simulated early-warning scenario, where partial discharge signals mixed with noise are analyzed and the model successfully generates predictive alarms. These results underscore the potential of integrating Rydberg-based broadband sensing with data-driven analysis for non-invasive, high-sensitivity diagnostics of electrical insulation systems. △ Less

Submitted 3 March, 2026; originally announced March 2026.

Comments: 10 pages, 6 figures. Published in Optics Express

Journal ref: Optics Express 34(4), 6426-6437 (2026)

Efficient first-principles modeling of complex molecular crystals at sub-chemical accuracy

Authors: Benjamin X. Shi, Kristina M. Herman, Flaviano Della Pia, Venkat Kapil, Andrea Zen, Peter R. Nagy, Sotiris Xantheas, Angelos Michaelides

Abstract: Molecules can form myriad crystalline polymorphs, each with distinct properties affecting their performance across diverse applications, from pharmaceuticals to functional materials and more. Predicting the thermodynamically most stable polymorph from first principles remains a formidable challenge. It requires methods that scale to large, technologically-relevant molecules while achieving very hi… ▽ More Molecules can form myriad crystalline polymorphs, each with distinct properties affecting their performance across diverse applications, from pharmaceuticals to functional materials and more. Predicting the thermodynamically most stable polymorph from first principles remains a formidable challenge. It requires methods that scale to large, technologically-relevant molecules while achieving very high accuracy (below 1 kJ/mol) on relative lattice energies. Such accuracy, often termed sub-chemical accuracy, is generally beyond the reach of the workhorse density functional theory (DFT). In this work, we introduce a framework, combining advances in correlated wavefunction theory (cWFT) and the many-body expansion, to deliver accurate, cost-effective predictions of complex molecular crystals. For 23 organic molecules and 13 ice polymorphs, we predict crystal lattice energies to within experimental uncertainties at costs comparable to hybrid DFT, while being several orders of magnitude more efficient than previous cWFT approaches. We extend this approach to a set of large, drug-like molecules including axitinib and ROY, previously inaccessible to cWFT and where DFT is insufficient, achieving sub-chemical accuracy on the relative energies between challenging polymorphs. With the reference data generated throughout this work, we have been able to further parametrize a DFT functional with unprecedented accuracy aligning with our predictions. This cWFT framework as well as DFT functional are made openly available, providing new ranking tools to facilitate efficient high-throughput screening of molecular crystal polymorphs. △ Less

Submitted 2 March, 2026; originally announced March 2026.

MACE-POLAR-1: A Polarisable Electrostatic Foundation Model for Molecular Chemistry

Authors: Ilyes Batatia, William J. Baldwin, Domantas Kuryla, Joseph Hart, Elliott Kasoar, Alin M. Elena, Harry Moore, Mikołaj J. Gawkowski, Benjamin X. Shi, Venkat Kapil, Panagiotis Kourtis, Ioan-Bogdan Magdău, Gábor Csányi

Abstract: Accurate modelling of electrostatic interactions and charge transfer is fundamental to computational chemistry, yet most machine learning interatomic potentials (MLIPs) rely on local atomic descriptors that cannot capture long-range electrostatic effects. We present a new electrostatic foundation model for molecular chemistry that extends the MACE architecture with explicit treatment of long-range… ▽ More Accurate modelling of electrostatic interactions and charge transfer is fundamental to computational chemistry, yet most machine learning interatomic potentials (MLIPs) rely on local atomic descriptors that cannot capture long-range electrostatic effects. We present a new electrostatic foundation model for molecular chemistry that extends the MACE architecture with explicit treatment of long-range interactions and electrostatic induction. Our approach combines local many-body geometric features with a non-self-consistent field formalism that updates learnable charge and spin densities through polarisable iterations to model induction, followed by global charge equilibration via learnable Fukui functions to control total charge and total spin. This design enables an accurate and physical description of systems with varying charge and spin states while maintaining computational efficiency. Trained on the OMol25 dataset of 100 million hybrid DFT calculations, our models achieve chemical accuracy across diverse benchmarks, with accuracy competitive with hybrid DFT on thermochemistry, reaction barriers, conformational energies, and transition metal complexes. Notably, we demonstrate that the inclusion of long-range electrostatics leads to a large improvement in the description of non-covalent interactions and supramolecular complexes over non-electrostatic models, including sub-kcal/mol prediction of molecular crystal formation energy in the X23-DMC dataset and a fourfold improvement over short-ranged models on protein-ligand interactions. The model's ability to handle variable charge and spin states, respond to external fields, provide interpretable spin-resolved charge densities, and maintain accuracy from small molecules to protein-ligand complexes positions it as a versatile tool for computational molecular chemistry and drug discovery. △ Less

Submitted 22 February, 2026; originally announced February 2026.

Practical and accurate density functionals for transition-metal heterogeneous catalysis

Authors: Benjamin X. Shi, Timothy C. Berkelbach

Abstract: Density functional theory (DFT) underpins modern atomistic simulations of transition-metal surfaces. It can predict key properties linked to catalytic performance, such as adsorption energies and barrier heights, enabling new paradigms in rational catalyst design. These applications require reliable density functionals, however achieving transition-metal chemical accuracy (13 kJ/mol) on these prop… ▽ More Density functional theory (DFT) underpins modern atomistic simulations of transition-metal surfaces. It can predict key properties linked to catalytic performance, such as adsorption energies and barrier heights, enabling new paradigms in rational catalyst design. These applications require reliable density functionals, however achieving transition-metal chemical accuracy (13 kJ/mol) on these properties remains challenging. We introduce a framework for designing new functionals tailored to catalytic processes on transition-metal surfaces, building on recent non-self-consistent approaches. Within this framework, we develop a hybrid and a double-hybrid functional that achieve unprecedented accuracy, with the latter reaching transition-metal chemical accuracy on average across 39 experimental adsorption reactions. In addition, both functionals demonstrate balanced performance for 17 barrier heights and correct qualitative failures of standard functionals, including CO adsorption on Pt(111) and graphene on Ni(111). They are computationally efficient, readily integrated into existing DFT codes, and supported by open-source workflows to facilitate adoption. More broadly, this framework provides a systematic route towards improved functionals for heterogeneous catalysis and complex materials. △ Less

Submitted 20 March, 2026; v1 submitted 16 February, 2026; originally announced February 2026.

Broadband Tunable Photon-Pair Generation and Spectrum Measurement Based on Noncritical Lithium Niobate Crystals

Authors: Zhao-Qi-Zhi Han, Bo-Wen Liu, He Zhang, Zhi-You Li, Xiao-Hua Wang, Jin-Peng Li, Zheng-He Zhou, Qi-Yu Chen, Yin-Hai Li, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Photon pairs play a vital role in modern science, driving extensive research into their generation. Yet, the narrow phase-matching bandwidth of conventional crystals has largely confined studies to specific wavelengths, leaving research on broadband tunable sources underexplored. Here, we employ a non-critical phase-matched lithium niobate (LN) crystal to generate widely tunable photon pairs. The… ▽ More Photon pairs play a vital role in modern science, driving extensive research into their generation. Yet, the narrow phase-matching bandwidth of conventional crystals has largely confined studies to specific wavelengths, leaving research on broadband tunable sources underexplored. Here, we employ a non-critical phase-matched lithium niobate (LN) crystal to generate widely tunable photon pairs. The generated near-infrared (NIR) photon pairs exhibit a high coincidence-to-accidental ratio (CAR > 20 dB) and are tunable across the 800-1600 nm range. We further showcase the utility of NIR photon pairs in spectroscopy by detecting carbon monoxide (CO) gas absorption. This approach will facilitate the design of advanced LN-based photonic experiments. △ Less

Submitted 12 February, 2026; originally announced February 2026.

Comments: 13 pages, 8 figures

Passive Incoherent Ultrafast Mid-Infrared Upconversion Imaging and Its Calibration

Authors: Jin-Peng Li, Zhi-You Li, Zhao-Qi-Zhi Han, Xiao-Hua Wang, He Zhang, Yin-Hai Li, Bo-Wen Liu, Wen-Tao Luo, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Ultrafast mid-infrared (MIR) imaging is a key enabling capability for monitoring transient thermal and plasma phenomena in scientific diagnostics and industrial safety. However, conventional cryogenic MIR cameras face a fundamental trade-off between frame rate, noise, and pixel format. Here we report a passive, incoherent MIR imaging platform that leverages sum-frequency upconversion in chirped pe… ▽ More Ultrafast mid-infrared (MIR) imaging is a key enabling capability for monitoring transient thermal and plasma phenomena in scientific diagnostics and industrial safety. However, conventional cryogenic MIR cameras face a fundamental trade-off between frame rate, noise, and pixel format. Here we report a passive, incoherent MIR imaging platform that leverages sum-frequency upconversion in chirped periodically poled lithium niobate (CPLN) to translate broadband 3--5um scenes to the near-infrared, enabling ultrafast acquisition on a silicon-based intensified CCD (iCCD). In fast-kinetics mode we achieve a physical frame rate of 100kHz with microsecond-scale gate control, and we directly capture the full evolution of an air-breakdown electric arc, resolving its rapid ignition, expansion, and decay dynamics. Beyond demonstrating ultrafast passive imaging, we introduce a drift-aware calibration workflow based on Allan deviation analysis to quantitatively select the gate width and averaging strategy under realistic slow-drift and multiplicative noise. This combined capability -- ultrafast passive MIR imaging plus operationally meaningful calibration -- provides a practical route toward real-time thermal surveillance and early-warning systems for hazardous fast transients. △ Less

Submitted 4 February, 2026; originally announced February 2026.

Comments: 13 pages,5 figures

Metrology-grade mid-infrared spectroscopy for multi-dimensional perception

Authors: Baoqi Shi, Chenxi Zhang, Ming-Yang Zheng, Yue Hu, Zeying Zhong, Zhenyuan Shang, Wenbo Ma, Xiu-Ping Xie, Xue Bai, Yi-Han Luo, Anting Wang, Hairun Guo, Qiang Zhang, Junqiu Liu

Abstract: The mid-infrared spectral window is essential for molecular fingerprinting and atmospheric sensing, yet unlocking its full potential is currently constrained by a fundamental instrumental trade-off: existing systems cannot simultaneously deliver broad bandwidth, high photon flux, and metrological frequency fidelity. Here, we resolve this bottleneck by demonstrating a metrology-grade spectroscopic… ▽ More The mid-infrared spectral window is essential for molecular fingerprinting and atmospheric sensing, yet unlocking its full potential is currently constrained by a fundamental instrumental trade-off: existing systems cannot simultaneously deliver broad bandwidth, high photon flux, and metrological frequency fidelity. Here, we resolve this bottleneck by demonstrating a metrology-grade spectroscopic system based on difference frequency generation, driven by widely tunable, near-infrared diode lasers traceable to atomic standards. Our system achieves continuous tunability across the 3-3.7 $μ$m atmospheric window and delivers output power exceeding 45 mW with an absolute frequency accuracy of 7.2 MHz. We harness this convergence to overcome a critical barrier in integrated photonics, unambiguously identifying and eliminating hydrogen-induced absorption in silicon nitride microresonators to achieve an 88-fold reduction in optical loss. We further reveal multi-phonon absorption in the silica cladding as the fundamental limit to mid-infrared integrated photonics. Finally, we demonstrate the system's versatility through scattering-resilient LiDAR capable of penetrating optically dense fog, and dual-modality sensing that simultaneously retrieves target distance and chemical composition. By unifying the rigor of frequency metrology with the versatility of broadband sensing, this architecture establishes a new paradigm for multi-dimensional perception in complex environments. △ Less

Submitted 31 January, 2026; originally announced February 2026.

Mid-infrared high-sensitive cavity-free in-situ CO gas sensing based on up-conversion detection

Authors: Zhao-Qi-Zhi Han, He Zhang, Fan Yang, Xiao-Hua Wang, Bo-Wen Liu, Jin-Peng Li, Zheng-He Zhou, Yin-Hai Li, Yan Li, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Carbon monoxide (CO) is a significant indicator gas with considerable application value in atmospheric monitoring, industrial production and medical diagnosis. Its fundamental vibrational band locates around 4.6 $\upmu$m and has larger absorption line strength than that of overtone band, which is more suitable for the precise identification and concentration detection of CO. In this paper, the up-… ▽ More Carbon monoxide (CO) is a significant indicator gas with considerable application value in atmospheric monitoring, industrial production and medical diagnosis. Its fundamental vibrational band locates around 4.6 $\upmu$m and has larger absorption line strength than that of overtone band, which is more suitable for the precise identification and concentration detection of CO. In this paper, the up-conversion detection is employed to convert the mid-infrared absorption signal obtained by TDLAS to the visible light band, then a silicon-based detector is utilized for detection. By which, we can achieve the highest sensitivity of 79.6 ppb under the condition of cavity-free in-situ with an absorption range length of only 0.14 m. Furthermore, the single-photon level real-time detection of CO concentration after the diffuse reflection is realized by using SPAD. This work demonstrates the merits of the up-conversion detection in terms of its functionality at room temperature and capacity for sensitivity detection. Furthermore, it presents a design and optimization methodology that has the potential to underpin the advancement of the method towards more practical applications, like industrial process monitoring, medical diagnosis and so on. △ Less

Submitted 20 May, 2026; v1 submitted 22 January, 2026; originally announced January 2026.

Density Limit Experiments and Core-localized Kinetic MHD Activities in HL-2A Ohmic Heating Plasmas

Authors: L. W. Hu, W. Chen, P. W. Shi, T. Long, J. Q. Xu, R. R. Ma, Y. G. Li, L. M. Yu, X. Yu, M. Jiang, T. F. Sun, J. M. Gao, Y. B. Dong, X. L. Zhu, Z. B. Shi

Abstract: The density limit is a mysterious barrier to magnetic confinement nuclear fusion, and is still an unresolved issue. In this paper, we will present the experimental results of the density limit and core-localized kinetic MHD instabilities on HL-2A. Firstly, the high density shots with $ne/ne_G>1$ have been achieved by the conventional gas-puff fuelling method in Ohmic heating plasmas, and the corre… ▽ More The density limit is a mysterious barrier to magnetic confinement nuclear fusion, and is still an unresolved issue. In this paper, we will present the experimental results of the density limit and core-localized kinetic MHD instabilities on HL-2A. Firstly, the high density shots with $ne/ne_G>1$ have been achieved by the conventional gas-puff fuelling method in Ohmic heating plasmas, and the corresponding duration time is close to $t\sim500$ ms ($\sim$ $30τ_E$), where $τ_E$ is the global energy confinement time. Secondly, it is found for the first time that there are kinetic MHD instabilities in the core plasmas while $ne/ne_G\sim1$. The analysis suggests that the core-localized MHD activities belong to Alfv{é}nic ion temperature gradient (AITG) modes or kinetic ballooning modes (KBM), and firstly it is found on experiment that they trigger the minor or major disruption of bulk plasmas while the density profile is peaked. These new findings are of great importance to figure out and understand the origin of the density limit. △ Less

Submitted 21 January, 2026; originally announced January 2026.

Comments: 15 pages, 13 figures

Enhanced multi-parameter metrology in dissipative Rydberg atom time crystals

Authors: Bang Liu, Jun-Rong Chen, Yu Ma, Qi-Feng Wang, Tian-Yu Han, Hao Tian, Yu-Hua Qian, Guang-Can Guo, Li-Hua Zhang, Bin-Bin Wei, Abolfazl Bayat, Dong-Sheng Ding, Bao-Sen Shi

Abstract: The pursuit of unprecedented sensitivity in quantum enhanced metrology has spurred interest in non-equilibrium quantum phases of matter and their symmetry breaking. In particular, criticality-enhanced metrology through time-translation symmetry breaking in many-body systems, a distinct paradigm compared to spatial symmetry breaking, is a field still in its infancy. Here, we have investigated the e… ▽ More The pursuit of unprecedented sensitivity in quantum enhanced metrology has spurred interest in non-equilibrium quantum phases of matter and their symmetry breaking. In particular, criticality-enhanced metrology through time-translation symmetry breaking in many-body systems, a distinct paradigm compared to spatial symmetry breaking, is a field still in its infancy. Here, we have investigated the enhanced sensing at the boundary of a continuous time-crystal (CTC) phase in a driven Rydberg atomic gas. By mapping the full phase diagram, we identify the parameter-dependent phase boundary where the time-translation symmetry is broken. This allows us to use a single setup for measuring multiple parameters, in particular frequency and amplitude of a microwave field. By increasing the microwave field amplitude, we first observe a phase transition from a thermal phase to a CTC phase, followed by a second transition into a distinct CTC state, characterized by a different oscillation frequency. Furthermore, we reveal the precise relationship between the CTC phase boundary and the scanning rate, displaying enhanced precision beyond the Standard Quantum Limit. This work not only provides a promising paradigm rooted in the critical properties of time crystals, but also advances a method for multi-parameter sensing in non-equilibrium quantum phases. △ Less

Submitted 15 January, 2026; originally announced January 2026.

Tabletop X-ray ghost video of moving objects

Authors: Hui Zeng, Ming-Fei Li, Zhi-Yue Yu, Bing-Zhan Shi, Xiao-Jing Wu, Jie Feng, Jin-Guang Wang, Yi-Fei Li, Ling-An Wu, Jian-Hong Shi, Li-Ming Chen

Abstract: X-ray imaging is widely employed in clinical medicine, industrial inspection, and various scientific research fields. Unfortunately, most currently used X-ray two-dimensional (2D) detectors suffer from a fundamental trade-off between the number of pixels and readout time, making them unsuitable for fast moving objects imaging, as well as the readout dead time causes frame losses. X-ray ghost imagi… ▽ More X-ray imaging is widely employed in clinical medicine, industrial inspection, and various scientific research fields. Unfortunately, most currently used X-ray two-dimensional (2D) detectors suffer from a fundamental trade-off between the number of pixels and readout time, making them unsuitable for fast moving objects imaging, as well as the readout dead time causes frame losses. X-ray ghost imaging (XGI) offers an alternative approach to image an object using only a highly sensitive single-pixel detector. However, a critical limitation of existing XGI methods is the excessive total acquisition time required, rendering it impractical for real applications. In this paper, we propose a rapid spatial modulation scheme based on random binary patterns encoded onto a fast-spinning mask. Clear X-ray visualization of moving objects is demonstrated with imaging rates up to 200 frames per second with a resolution of 225 um. For the first time, our method has greatly improved the XGI imaging speed and paves the way for X-ray imaging application of motion objects, such as the inspection of rotating aero-engines and in vivo medical imaging. △ Less

Submitted 1 January, 2026; originally announced January 2026.

A unified MRT-LB framework for Navier-Stokes and nonlinear convection-diffusion equations and beyond: moment equations, auxiliary moments, multispeed lattices, and Hermite matrices

Authors: Baochang Shi, Xiaolei Yuan, Zhenhua Chai

Abstract: We develop a unified multi-relaxation-time lattice Boltzmann (MRT-LB) framework based on discrete Hermite polynomials (Hermite matrices) for the Navier-Stokes equations (NSEs) and nonlinear convection-diffusion equations (NCDEs), using multispeed rectangular lattice (rD$d$Q$b$) models. For NSEs, the proposed MRT-LB model simulates incompressible and compressible isothermal flows in both single-pha… ▽ More We develop a unified multi-relaxation-time lattice Boltzmann (MRT-LB) framework based on discrete Hermite polynomials (Hermite matrices) for the Navier-Stokes equations (NSEs) and nonlinear convection-diffusion equations (NCDEs), using multispeed rectangular lattice (rD$d$Q$b$) models. For NSEs, the proposed MRT-LB model simulates incompressible and compressible isothermal flows in both single-phase and multiphase systems. Macroscopic moment equations are derived from the MRT-LB model via the direct Taylor expansion method. By selecting appropriate fundamental moments, the target NSEs and NCDE are recovered from these moment equations. Critically, the elimination of spurious terms and/or the recovery of the desired terms relies on specific auxiliary moments: the second-order auxiliary moment ($\mathbf{M}_{2G}$) of the source term distribution function (SDF) and the third-order auxiliary moment ($\mathbf{M}_{30}$) of the equilibrium distribution function (EDF) for NSEs, as well as the first-order auxiliary moment ($\mathbf{M}_{1G}$) of the SDF and the second-order auxiliary moment ($\mathbf{M}_{20}$) of the EDF for NCDE. Furthermore, using the weighted orthogonality of Hermite matrices, we establish essential relations for weight coefficients and construct several multispeed rectangular lattice models, including rD2Q25 and rD3Q53, with subgroup models rD2Q21, rD2Q17, rD2Q13, rD3Q45, and rD3Q33. A generalized third-order equilibrium distribution function is derived. We emphasize that for rectangular lattices, specific elements of the Hermite matrix corresponding to third-order discrete Hermite polynomials require correction to satisfy weighted orthogonality. △ Less

Submitted 18 December, 2025; originally announced December 2025.

Comments: 33 pages, 1 figure

Structures resistant to Manipulation by all Wavefronts in two dimensions

Authors: Asher Sabbagh, Michael Horodynski, Rida Khan, Brian Shi, Marin Soljačić

Abstract: Using light to manipulate small particles is a powerful tool with numerous practical applications across biophysics and nanotechnology. This experimental technique has achieved significant performance gains by employing shaped wavefronts, most commonly generated with spatial light modulators. Wavefront shaping has also enabled the manipulation of seemingly arbitrary objects beyond the reach of con… ▽ More Using light to manipulate small particles is a powerful tool with numerous practical applications across biophysics and nanotechnology. This experimental technique has achieved significant performance gains by employing shaped wavefronts, most commonly generated with spatial light modulators. Wavefront shaping has also enabled the manipulation of seemingly arbitrary objects beyond the reach of conventional beams. Contrary to this established assumption, we show here the existence of a wide variety of objects resistant to manipulation, even with the optimal wavefront shaping protocol. The counterintuitive shapes of these objects are found using inverse design in two dimensions, providing a foundation for their natural extension to three dimensions. Specifically, we show that the maximal pulling force is reduced by up to four orders of magnitude, and the maximal trapping stiffness is reduced by up to nearly two orders of magnitude. Our findings could prove useful for the development of micromachines that require a predictable mechanical response to arbitrary waves. △ Less

Submitted 13 March, 2026; v1 submitted 10 December, 2025; originally announced December 2025.

Widely tunable cavity-enhanced backward difference-frequency generation

Authors: Ming-Yuan Gao, Yue-Wei Song, Ren-Hui Chen, Yin-Hai Li, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Difference-frequency generation (DFG) is a powerful technique for generating widely tunable infrared radiation. However, conventional phase-matching schemes may require tuning multiple parameters-such as the wavelengths, crystal temperature, crystal angle, and poling period-to achieve wide tunability, which increases the complexity of practical operation. In this work, we employ a backward quasi-p… ▽ More Difference-frequency generation (DFG) is a powerful technique for generating widely tunable infrared radiation. However, conventional phase-matching schemes may require tuning multiple parameters-such as the wavelengths, crystal temperature, crystal angle, and poling period-to achieve wide tunability, which increases the complexity of practical operation. In this work, we employ a backward quasi-phase-matching scheme with distinctive tuning characteristics and demonstrate pump-enhanced continuous-wave DFG output tunable from 1751 nm to 2451 nm (700 nm range) in a bulk crystal. The tuning is achieved solely by varying the pump wavelength and the signal wavelength (less than 5 nm), enabling continuous, rapid, and room-temperature operation. The tuning characteristics, power-scaling behavior, and output stability are experimentally verified with the idler wavelength set at 2000 nm. The approach offers a new paradigm for widely tunable infrared radiation generation and holds promise for applications in spectroscopy and biomedical sensing. △ Less

Submitted 17 October, 2025; originally announced October 2025.

Light coupling to photonic integrated circuits using optimized lensed fibers

Authors: Dengke Chen, Zeying Zhong, Sanli Huang, Jiahao Sun, Sicheng Zeng, Baoqi Shi, Yi-Han Luo, Junqiu Liu

Abstract: Efficient and reliable light coupling between optical fibers and photonic integrated circuits has arguably been the most essential issue in integrated photonics for optical interconnects, nonlinear signal conversion, neuromorphic computing, and quantum information processing. A commonly used approach is to use inverse tapers interfacing with lensed fibers, particularly for waveguides of relatively… ▽ More Efficient and reliable light coupling between optical fibers and photonic integrated circuits has arguably been the most essential issue in integrated photonics for optical interconnects, nonlinear signal conversion, neuromorphic computing, and quantum information processing. A commonly used approach is to use inverse tapers interfacing with lensed fibers, particularly for waveguides of relatively low refractive index, such as silicon nitride (Si3N4), silicon oxynitride, and lithium niobate. This approach simultaneously enables broad operation bandwidth, high coupling efficiency, and simplified fabrication. Although diverse taper designs have been invented and characterized to date, lensed fibers play equally important roles here, yet their optimization has long been underexplored. Here, we fill this gap and introduce a comprehensive co-optimization strategy that synergistically refines the geometries of the taper and the lensed fiber. By incorporating the genuine lensed fiber's shape into the simulation, we accurately capture its non-Gaussian emission profile, thereby nullifying the widely accepted approximation based on a paraxial Gaussian mode. We further characterize many lensed fibers and Si3N4 tapers of varying shapes using different fabrication processes. Our experimental and simulation results show remarkable agreement, both achieving maximum coupling efficiencies exceeding 80% per facet. Finally, we summarize the optimal choices of lensed fibers and Si3N4 tapers that can be directly deployed in modern CMOS foundries for scalable manufacturing of Si3N4 photonic integrated circuits. Our study not only contributes to light-coupling solutions but is also critical for photonic packaging and optoelectronic assemblies that are currently revolutionizing data centers and AI. △ Less

Submitted 15 October, 2025; v1 submitted 12 October, 2025; originally announced October 2025.

Report number: 014078

Journal ref: Phys. Rev. Applied 25, 014078 (2026)

Observation of Discrete Time Quasicrystal in Rydberg Atomic Gases

Authors: Dong-Yang Zhu, Zheng-Yuan Zhang, Qi-Feng Wang, Yu Ma, Tian-Yu Han, Chao Yu, Qiao-Qiao Fang, Shi-Yao Shao, Qing Li, Ya-Jun Wang, Jun Zhang, Han-Chao Chen, Xin Liu, Jia-Dou Nan, Yi-Ming Yin, Li-Hua Zhang, Guang-Can Guo, Bang Liu, Dong-Sheng Ding, Bao-Sen Shi

Abstract: Discrete time quasicrystals (DTQC) constitute a class of non-equilibrium matter characterized by temporal order without strict periodicity, in contrast to conventional time crystals. Investigating these phenomena is essential for expanding our fundamental understanding of far-from-equilibrium quantum matter and spontaneous symmetry breaking beyond periodic regimes. Here, we experimentally observe… ▽ More Discrete time quasicrystals (DTQC) constitute a class of non-equilibrium matter characterized by temporal order without strict periodicity, in contrast to conventional time crystals. Investigating these phenomena is essential for expanding our fundamental understanding of far-from-equilibrium quantum matter and spontaneous symmetry breaking beyond periodic regimes. Here, we experimentally observe a DTQC in a driven-dissipative ensemble of strongly interacting Rydberg atoms, displaying non-equilibrium dynamical response with a different finite Abelian group symmetry $\mathbb{Z}{_m} \times \mathbb{Z}{_n}$. By applying a quasi-periodic drive using a dual-frequency drive with incommensurate frequencies, we demonstrate that the system exhibits a robust subharmonic response at multiple incommensurate frequencies, signifying the emergence of a DTQC phase. We map the full phase diagram of the system, which includes the DTQC phase, and demonstrated its rigidity against perturbations in both RF field intensity and laser detuning. Moreover, we observe a cyclic group symmetry effect that constrains the construction of $\mathbb{Z}{_2} \times \mathbb{Z}{_3}$-symmetric DTQC. This work establishes a versatile platform for studying non-equilibrium phases of matter and provides insights into the dynamics of time-translation symmetry breaking in quantum many-body systems. △ Less

Submitted 25 September, 2025; originally announced September 2025.

Short-wave infrared broadband up-conversion imaging by using a noncritical phase matched bulk KTiOPO$_4$ crystal

Authors: Xiaohua Wang, Zhaoqizhi Han, Zhenghe Zhou, Jinpeng Li, Bowen Liu, He Zhang, Yinhai Li, Zhiyuan Zhou, Baosen Shi

Abstract: Compared to cryogenically cooled conventional detectors, up-conversion detection enables efficient room-temperature short-wave infrared (SWIR) imaging. Although quasi-phase-matching (QPM) in periodically poled crystals offers advantages, the small crystal aperture (typically 1 mm$\times$3 mm) limits resolution. Non-poled crystals enable larger apertures but suffer walk-off aberrations. This work o… ▽ More Compared to cryogenically cooled conventional detectors, up-conversion detection enables efficient room-temperature short-wave infrared (SWIR) imaging. Although quasi-phase-matching (QPM) in periodically poled crystals offers advantages, the small crystal aperture (typically 1 mm$\times$3 mm) limits resolution. Non-poled crystals enable larger apertures but suffer walk-off aberrations. This work overcomes these limitations by using a noncritical phase matched (NCPM) KTiOPO$_4$ crystal (6 mm$\times$7 mm aperture, 0.5 mm length). Results show resolutions 6$\times$ and 2$\times$ higher than periodically poled crystals in orthogonal directions, with broad conversion band (1.3-2.2 $μ$m) covering biological and atmospheric windows. The absence of walk-off ensures better image fidelity in up-conversion process. This study presents the first comprehensive characterization of NCPM-based broadband up-conversion imaging, demonstrating performance at the theoretical resolution limit while circumventing drawbacks inherent in alternative up-conversion schemes and conventional detectors. △ Less

Submitted 25 September, 2025; originally announced September 2025.

Observation of tuning properties in a doubly resonant backward optical parametric oscillator

Authors: Ming-Yuan Gao, Yue-Wei Song, Zhi-Cheng Guo, Yin-Hai Li, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Doubly resonant optical parametric oscillators (OPOs) under continuous wave (CW) pumping are particularly notable for their low threshold and narrow linewidth. Backward OPOs (BOPOs) realized through backward quasi-phase matching which exhibit unique tuning properties compared with conventional forward OPOs have been demonstrated under pulse pumping. In this work, a doubly resonant BOPO was impleme… ▽ More Doubly resonant optical parametric oscillators (OPOs) under continuous wave (CW) pumping are particularly notable for their low threshold and narrow linewidth. Backward OPOs (BOPOs) realized through backward quasi-phase matching which exhibit unique tuning properties compared with conventional forward OPOs have been demonstrated under pulse pumping. In this work, a doubly resonant BOPO was implemented in a semi-monolithic cavity under CW pumping, and its tuning properties were characterized. By tuning the pump wavelength, the forward and backward waves exhibited tuning ranges of 56.85 nm and 0.89 nm, respectively. Adjusting the crystal temperature resulted in tuning ranges of 59.7 GHz and 59.4 GHz for the forward and backward waves, respectively. This research establishes the BOPO as a promising candidate for applications in the field of CW OPOs. △ Less

Submitted 25 September, 2025; originally announced September 2025.

Cavity-enhanced symmetric second-harmonic generation

Authors: Ming-Yuan Gao, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: As one of the two types of backward second-harmonic generation (SHG), symmetric SHG exhibits some physical characteristics and application prospects that are distinct from those of forward SHG. It is generally realized through quasi-phase matching, which imposes more stringent requirements on the poling period and thus presents challenges for domain engineering. Although employing larger poling pe… ▽ More As one of the two types of backward second-harmonic generation (SHG), symmetric SHG exhibits some physical characteristics and application prospects that are distinct from those of forward SHG. It is generally realized through quasi-phase matching, which imposes more stringent requirements on the poling period and thus presents challenges for domain engineering. Although employing larger poling periods can ease fabrication, it inevitably reduces conversion efficiency, a drawback that can be compensated by using a cavity. In this work, we employed a semi-monolithic cavity to enhance the efficiency of 7th-order symmetric SHG, achieving a measured one-sided conversion efficiency of 7.2 %, which corresponds to a theoretical total efficiency of 14.4 %. This represents an improvement of more than three orders of magnitude compared with the single-pass case. In addition, the nonlinear coefficient of the crystal of ${d_{33}} = 4.8$ $\rm pm/V$ was estimated. △ Less

Submitted 24 September, 2025; originally announced September 2025.

The Good, the Bad, and the Ugly of Atomistic Learning for "Clusters-to-Bulk" Generalization

Authors: Mikołaj J. Gawkowski, Mingjia Li, Benjamin X. Shi, Venkat Kapil

Abstract: Training machine learning interatomic potentials (MLIPs) on total energies of molecular clusters using differential or transfer learning is becoming a popular route to extend the accuracy of correlated wave-function theory to condensed phases. A key challenge, however, lies in validation, as reference observables in finite-temperature ensembles are not available at the reference level. Here, we co… ▽ More Training machine learning interatomic potentials (MLIPs) on total energies of molecular clusters using differential or transfer learning is becoming a popular route to extend the accuracy of correlated wave-function theory to condensed phases. A key challenge, however, lies in validation, as reference observables in finite-temperature ensembles are not available at the reference level. Here, we construct synthetic reference data from pretrained MLIPs and evaluate the generalizability of cluster-trained models on ice-Ih, considering scenarios where both energies and forces and where only energies are available for training. We study the accuracy and data-efficiency of differential, single-fidelity transfer, and multi-fidelity transfer learning against ground-truth thermodynamic observables. We find that transferring accuracy from clusters to bulk requires regularization, which is best achieved through multi-fidelity transfer learning when training on both energies and forces. By contrast, training only on energies introduces artefacts: stable trajectories and low energy errors conceal large force errors, leading to inaccurate microscopic observables. More broadly, we show that accurate reproduction of microscopic structure correlates strongly with low force errors but only weakly with energy errors, whereas global properties such as energies and densities correlate with low energy errors. This highlights the need to incorporate forces during training or to apply careful validation before production. Our results highlight the promise and pitfalls of cluster-trained MLIPs for condensed phases and provide guidelines for developing - and critically, validating - robust and data-efficient MLIPs. △ Less

Submitted 20 September, 2025; originally announced September 2025.

Ultrashort Time-Integrated Diagnosis of Laser-Heated Deuterium Ions in Dense Plasma via Fusion Neutron Spectra

Authors: Jie Feng, Hao Xu, Mingxuan Wei, Mingyang Zhu, Xichen Hu, Bingzhan Shi, Fuyuan Wu, Weijun Zhou, Wenchao Yan, Guoqiang Zhang, Jinguang Wang, Yifei Li, Xin Lu, Liming Chen

Abstract: The ultrashort time-integrated diagnosis of ions plays a vital role in high energy density physics research. However, it is extremely challenging to measure in experiment. Here, we demonstrate a reliable approach for investigating the dynamics of deuterium ions in dense plasma. By irradiating a heavy water stream with the hundred Hertz repetitive intense femtosecond laser pulses, the neutrons from… ▽ More The ultrashort time-integrated diagnosis of ions plays a vital role in high energy density physics research. However, it is extremely challenging to measure in experiment. Here, we demonstrate a reliable approach for investigating the dynamics of deuterium ions in dense plasma. By irradiating a heavy water stream with the hundred Hertz repetitive intense femtosecond laser pulses, the neutrons from D(D,n)3He reaction can be detected via a single Time-of-Flight detector to accumulate the spectrum with a fine energy-resolution. This spectrum has been utilized to calculate the temperature and angular distribution of deuterium ions transported in plasma. And the calculated results are well verified by particle-in-cell simulations of deuterium ions dynamics. Our method paves a new way for diagnosing ions picoseconds time-integrated dynamics in plasma and holds great potential for understanding the ions transport process in high-energy density matters and studying laser plasma ion acceleration. △ Less

Submitted 30 August, 2025; originally announced September 2025.

Towards Routine Condensed Phase Simulations with Delta-Learned Coupled Cluster Accuracy: Application to Liquid Water

Authors: Niamh O'Neill, Benjamin X. Shi, William Baldwin, William C. Witt, Gábor Csányi, Julian D. Gale, Angelos Michaelides, Christoph Schran

Abstract: Simulating liquid water to an accuracy that matches its wealth of available experimental data requires both precise electronic structure methods and reliable sampling of nuclear (quantum) motion. This is challenging because applying the electronic structure method of choice - coupled cluster theory with single, double and perturbative triple excitations [CCSD(T)] - to condensed phase systems is cu… ▽ More Simulating liquid water to an accuracy that matches its wealth of available experimental data requires both precise electronic structure methods and reliable sampling of nuclear (quantum) motion. This is challenging because applying the electronic structure method of choice - coupled cluster theory with single, double and perturbative triple excitations [CCSD(T)] - to condensed phase systems is currently limited by its computational cost and complexity. Recent tour-de-force efforts have demonstrated that this accuracy can indeed bring simulated liquid water into close agreement with experiment using machine learning potentials (MLPs). However, achieving this remains far from routine, requiring large datasets and significant computational cost. In this work, we introduce a practical approach that combines developments in MLPs with local correlation approximations to enable routine CCSD(T)-level simulations of liquid water. When combined with nuclear quantum effects, we achieve agreement to experiments for structural and transport properties. Crucially, this approach extends beyond constant volume to constant pressure simulations, allowing fundamental properties such as the density to now be predicted by MLP-based CCSD(T) models. Importantly, the approach also handles constant pressure simulations, enabling MLP-based CCSD(T) models to predict isothermal-isobaric bulk properties, such as water's density maximum in close agreement with experiment. Encompassing tests across electronic structure, datasets and MLP architecture, this work provides a practical blueprint towards routinely developing CCSD(T)-based MLPs for the condensed phase. △ Less

Submitted 18 August, 2025; originally announced August 2025.

Generation of Near-ideal Indistinguishable Two-Photon State by Incoherent Light

Authors: Yue-Wei Song, Ming-Yuan Gao, Zhi-Cheng Guo, Zheng-He Zhou, Yin-Hai Li, Guang-Can Guo, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: High-quality quantum states lie at the heart of advanced quantum information processing. The degree of photon indistinguishability is critical for applications from photonic quantum computation to precision metrology. The two-photon Hong-Ou-Mandel (HOM) interference effect provides a rigorous quantification method, with its visibility serving as the ultimate benchmark for source quality. Generally… ▽ More High-quality quantum states lie at the heart of advanced quantum information processing. The degree of photon indistinguishability is critical for applications from photonic quantum computation to precision metrology. The two-photon Hong-Ou-Mandel (HOM) interference effect provides a rigorous quantification method, with its visibility serving as the ultimate benchmark for source quality. Generally, the coherent pumping is widely regarded as indispensable for the preparation of quantum sources. As a result, incoherent light sources have seen limited applications in the current quantum technologies. In this work, we generate an indistinguishable two-photon state by incoherent light generated by frequency doubling of Amplified Spontaneous Emission light. The theoretical analysis indicates that phase randomization of the pumping does not affect the coincidence visibility in two-photon intensity interference. Moreover, temporal incoherence further enhances the symmetry of the generated spectrum in second-harmonic generation. In the experiment, the incoherently pumped photon sources exhibit a heralding efficiency of approximately 60\% and a coincidence-to-accidental ratio exceeding 15000. The observed HOM interference fringes show the visibility of 99.1\% without any spectrum filtering, confirming the near-ideal indistinguishability of the photons. Our study reveals the role of temporal coherence in second-order nonlinear interactions, it provide a potential approach to use an easily accessible incoherent light for engineering high-quality quantum sources. △ Less

Submitted 16 July, 2025; originally announced July 2025.

All-optical convolution utilizing processing in memory based on a cold atomic ensemble

Authors: Ying-Hao Ye, Jia-Qi Jiang, En-Ze Li, Wei Zhang, Da-Chuang Li, Zhi-Han Zhu, Dong-Sheng Ding, Bao-Sen Shi

Abstract: Processing in memory (PIM) has received significant attention due to its high efficiency, low latency, and parallelism. In optical computation, coherent memory is a crucial infrastructure for PIM frameworks. This study presents an all-optical convolution experiment conducted within computational storage based on a cold atomic ensemble. By exploiting the light-atom phase transfer facilitated by the… ▽ More Processing in memory (PIM) has received significant attention due to its high efficiency, low latency, and parallelism. In optical computation, coherent memory is a crucial infrastructure for PIM frameworks. This study presents an all-optical convolution experiment conducted within computational storage based on a cold atomic ensemble. By exploiting the light-atom phase transfer facilitated by the electromagnetically induced transparency, we demonstrated spiral phase contrast processing of photon images in memory, resulting in the edge enhancement of retrieved images recorded using time-correlated photon imaging. In particular, adopting state-of-the-art atomic techniques provides a coherent memory lifetime exceeding 320 us for PIM operations. Our results highlight the significant potential of cold atomic ensembles as computational storage for developing all-optical PIM systems. △ Less

Submitted 17 June, 2025; originally announced June 2025.

Comments: 6 pages, 3 figures, supplmental material appended

Cascaded quantum time transfer breaking the no-cloning barrier with entanglement relay architecture

Authors: H. Hong, X. Xiang, R. Quan, B. Shi, Y. Liu, Z. Xia, T. Liu, X. Li, M. Cao, S. Zhang, K. Guo, R. Dong

Abstract: Quantum two-way time transfer (Q-TWTT) leveraging energy-time entangled biphotons has achieved sub-picosecond stability but faces fundamental distance limitations due to the no-cloning theorem's restriction on quantum amplification. To overcome this challenge, we propose a cascaded Q-TWTT architecture employing relay stations that generate and distribute new energy-time entangled biphotons after e… ▽ More Quantum two-way time transfer (Q-TWTT) leveraging energy-time entangled biphotons has achieved sub-picosecond stability but faces fundamental distance limitations due to the no-cloning theorem's restriction on quantum amplification. To overcome this challenge, we propose a cascaded Q-TWTT architecture employing relay stations that generate and distribute new energy-time entangled biphotons after each transmission segment. Theoretical modeling reveals sublinear standard deviation growth (merely N increase for N equidistant segments), enabling preservation of sub-picosecond stability over extended distances. We experimentally validate this approach using a three-station cascaded configuration over 200 km fiber segments, demonstrating strong agreement with theory. Utilizing independent Rb clocks at end and relay stations with online frequency skew correction, we achieve time stabilities of 3.82 ps at 10 s and 0.39 ps at 5120 s. The consistency in long-term stability between cascaded and single-segment configurations confirms high-precision preservation across modular quantum networks. This work establishes a framework for long-distance quantum time transfer that surpasses the no-cloning barrier, providing a foundation for future quantum-network timing infrastructure. △ Less

Submitted 15 June, 2025; originally announced June 2025.

High resolution up-conversion imaging in the 10 μm band under incoherent illumination

Authors: Zhao-Qi-Zhi Han, Xiao-Hua Wang, Jin-Peng Li, Bo-Wen Liu, Zheng-He Zhou, He Zhang, Yin-Hai Li, Zhi-Yuan Zhou, Bao-Sen Shi

Abstract: Long-wavelength infrared band exhibits significant utility in thermal signature acquisition and molecular spectral analysis, among other applications. The up-conversion detection technique enables effective signal transduction into the detection bandwidth of silicon-based photodetectors, thereby facilitating high-sensitivity photonic measurements. We realized high-resolution up-conversion imaging… ▽ More Long-wavelength infrared band exhibits significant utility in thermal signature acquisition and molecular spectral analysis, among other applications. The up-conversion detection technique enables effective signal transduction into the detection bandwidth of silicon-based photodetectors, thereby facilitating high-sensitivity photonic measurements. We realized high-resolution up-conversion imaging for incoherent thermal targets in the 10 μm spectral regime for the first time. Furthermore, this work presents the first derivation of analytical models characterizing depth of field and astigmatic aberration in up-conversion imaging systems, which show excellent agreement between theoretical and experimental results. The results demonstrate generalisability to various up-conversion imaging systems, thus providing critical insights for the design and optimisation of such systems. △ Less

Submitted 30 May, 2025; originally announced May 2025.

Equilibrium-distribution-function based mesoscopic finite-difference methods for partial differential equations: Modeling and Analysis

Authors: Baochang shi, Rui Du, Zhenhua Chai

Abstract: In this paper, based on the idea of direct discrete modeling (DDM) with equilibrium distribution functions (EDFs), we develop a general framework of the mesoscopic numerical method (MesoNM) for macroscopic partial differential equations (PDEs), including but not limited to the nonlinear convection-diffusion equation (NCDE) and the Navier-Stokes equations (NSEs). Unlike the mesoscopic lattice Boltz… ▽ More In this paper, based on the idea of direct discrete modeling (DDM) with equilibrium distribution functions (EDFs), we develop a general framework of the mesoscopic numerical method (MesoNM) for macroscopic partial differential equations (PDEs), including but not limited to the nonlinear convection-diffusion equation (NCDE) and the Navier-Stokes equations (NSEs). Unlike the mesoscopic lattice Boltzmann method, this kind of MesoNM is an EDF-based mesoscopic finite-difference (MesoFD) method, and by taking the moments of the MesoFD scheme, its macroscopic version, called MMFD method, can be derived directly. Both MesoFD scheme and MMFD schemes are multi-level FD methods, MesoFD scheme being mesoscopic, and MMFD scheme being its macroscopic form which has the form of the central FD scheme. They are unified FD schemes for PDEs and can be in implicit or explicit forms as needed. The macroscopic moment equations (MEs) can be derived from the MesoFD or MMFD scheme through the Taylor expansion method, and the common PDEs can be recovered from the MEs by using the direct Taylor expansion method. Moreover, the stability of the MMFD scheme is analyzed for linear CDE and liner wave equation with anisotropic diffusion, and the stability conditions of a two-level explicit MMFD scheme, a two-level $θ$-MMFD scheme (hybrid explicit and implicit MMFD scheme), and a three-level MMFD scheme are obtained, respectively. Finally, we note that some existing lattice Boltzmann (LB) based macroscopic FD models for the NSEs and NCDE are the special cases of present MMFD, which can be considered as a unified framework of FD schemes for PDEs, from this point of view. △ Less

Submitted 11 June, 2025; v1 submitted 17 May, 2025; originally announced May 2025.

Photonic Networking of Quantum Memories in High-Dimensions

Authors: Mikhail Shalaev, Sagnik Saha, George Toh, Isabella Goetting, Ashish Kalakuntla, Harriet Bufan Shi, Jameson O'Reilly, Yichao Yu, Christopher Monroe

Abstract: Quantum networking enables the exchange of quantum information between physically separated quantum systems, which has applications ranging from quantum computing to unconditionally secure communication. Such quantum information is generally represented by two-level quantum systems or qubits. Here, we demonstrate a quantum network of high-dimensional (HD) quantum memories or ``qudits" stored in in… ▽ More Quantum networking enables the exchange of quantum information between physically separated quantum systems, which has applications ranging from quantum computing to unconditionally secure communication. Such quantum information is generally represented by two-level quantum systems or qubits. Here, we demonstrate a quantum network of high-dimensional (HD) quantum memories or ``qudits" stored in individual atoms. The interference and detection of HD time-bin encoded single photons emitted from atomic qudit memories heralds maximally-entangled Bell states across pairs of atomic qudit levels. This approach expands the quantum information capacity of a quantum network while improving the entanglement success fraction beyond the standard 50\% limit of qubit-based measurement protocols. △ Less

Submitted 16 May, 2025; originally announced May 2025.

Hybrid-integrated dark-pulse microcombs towards visible light spectrum

Authors: Jinbao Long, Xiaoying Yan, Sanli Huang, Wei Sun, Hao Tan, Zeying Zhong, Zhenyuan Shang, Jiahao Sun, Baoqi Shi, Chen Shen, Yi-Han Luo, Junqiu Liu

Abstract: Leveraging hybrid integration, we demonstrate dark-pulse formation at 780-nm wavelength band in integrated Si$_3$N$_4$ microresonators driven by high-power AlGaAs-based chip-scale lasers. The device outputs coherent frequency combs with electronically detectable repetition rates down to 20 GHz, paving a route to efficient and compact atom-chip interfaces for spectroscopy, metrology and sensing. Leveraging hybrid integration, we demonstrate dark-pulse formation at 780-nm wavelength band in integrated Si$_3$N$_4$ microresonators driven by high-power AlGaAs-based chip-scale lasers. The device outputs coherent frequency combs with electronically detectable repetition rates down to 20 GHz, paving a route to efficient and compact atom-chip interfaces for spectroscopy, metrology and sensing. △ Less

Submitted 1 May, 2025; originally announced May 2025.

Non-invasive mid-circuit measurement and reset on atomic qubits

Authors: Zuo-Yao Chen, Isabella Goetting, George Toh, Yichao Yu, Mikhail Shalaev, Sagnik Saha, Ashish Kalakuntla, Harriet Bufan Shi, Christopher Monroe, Alexander Kozhanov, Crystal Noel

Abstract: Mid-circuit measurement and reset of subsets of qubits is a crucial ingredient of quantum error correction and many quantum information applications. Measurement of atomic qubits is accomplished through resonant fluorescence, which typically disturbs neighboring atoms due to photon scattering. We propose and prototype a new scheme for measurement that provides both spatial and spectral isolation b… ▽ More Mid-circuit measurement and reset of subsets of qubits is a crucial ingredient of quantum error correction and many quantum information applications. Measurement of atomic qubits is accomplished through resonant fluorescence, which typically disturbs neighboring atoms due to photon scattering. We propose and prototype a new scheme for measurement that provides both spatial and spectral isolation by using tightly-focused individual laser beams and narrow atomic transitions. The unique advantage of this scheme is that all operations are applied exclusively to the read-out qubit, with negligible disturbance to the other qubits of the same species and little overhead. In this letter, we pave the way for non-invasive and high fidelity mid-circuit measurement and demonstrate all key building blocks on a single trapped barium ion. △ Less

Submitted 28 October, 2025; v1 submitted 16 April, 2025; originally announced April 2025.

Comments: 11 pages, 9 figures

Journal ref: Phys. Rev. A 113, 012606 (2026)

An all optical broadband tunable quantum frequency shifter

Authors: Li Chen, Zhi-Yuan Zhou, Ming-Yuan Gao, Wu-Zhen L, Zhao-Qi-Zhi Han, Yue-Wei Song, Ren-Hui Chen, Bao-Sen Shi

Abstract: A frequency shifter of the photon is a key component for frequency-multiplexed high-capacity quantum communications and frequency-encoded quantum computation. Existed methods for shifting the frequency of a photon based on electro-optical, or acousto-optical effect, however, suffer the limited frequency shift up to a few hundreds of GHz, furthermore, high-quality micro-wave electronics are require… ▽ More A frequency shifter of the photon is a key component for frequency-multiplexed high-capacity quantum communications and frequency-encoded quantum computation. Existed methods for shifting the frequency of a photon based on electro-optical, or acousto-optical effect, however, suffer the limited frequency shift up to a few hundreds of GHz, furthermore, high-quality micro-wave electronics are required. The frequency of a photon can also be shifted with the frequency difference equal to the frequency of pump laser by using an all optical-wave-mixing approach, which is usually about tens of THz. So, there is a big frequency shifting gap between these methods. Here, we propose a new scheme of a quantum frequency shifter based on an all-optical wave-mixing process, which can theoretically achieve a frequency shift ranging from GHz to a few THz, therefore bridging the gap. As a principle of poof, by using two pump beams in a three-wave mixing cascading process, a heralded single photon is frequency-shifted more than 400GHz, and the shift can be tuned continuously over broadband by changing the frequency difference between two pump lasers. Besides, high coincidence to accidence ratio between the shifted photons and the heralded photon indicates the preserve of quantum properties. The present quantum frequency shifter is in analog to an electro-optical based shifter, but with much broader tuning ability. Our all-optical quantum frequency shifter will become a fundamental building block for high-speed quantum communication networks and frequency domain photonic quantum computation. △ Less

Submitted 7 April, 2025; originally announced April 2025.

Super-resolution measurement of thermo-optic coefficient of KTP crystal based on phase amplification

Authors: Wuzhen Li, Zhiyuan Zhou, Guangcan Guo, Baosen Shi

Abstract: Given that the phase amplification method based on harmonic generation exhibits significant phase super-resolution capability in interferometric precision measurement, extending this technology to birefringence interferometers to achieve super-resolution characterization of birefringent crystal properties has important research significance and application value. Here, we achieve a four-fold enhan… ▽ More Given that the phase amplification method based on harmonic generation exhibits significant phase super-resolution capability in interferometric precision measurement, extending this technology to birefringence interferometers to achieve super-resolution characterization of birefringent crystal properties has important research significance and application value. Here, we achieve a four-fold enhancement in the measurement resolution of the thermo-optic coefficient of a KTiOPO4 crystal by combining a self-stabilized birefringence interferometer with cascaded second harmonic generation processes. We observe the tunable interference beating phenomenon by rotating a birefringent crystal versus the temperature of the crystal for the fundamental wave, second harmonic, and fourth harmonic. Furthermore, the fourth harmonic interference fringes beat 4 times faster than the fundamental wave interference fringes. This beating effect is used to determine the thermo-optic coefficients of the two principal refractive axes with a single measurement. This work provides a feasible, real-time, and robust method for super-resolution measurements based on birefringence interferometry. △ Less

Submitted 11 March, 2025; originally announced March 2025.

Comments: 8 pages; 4 figures

Space compatibility of emerging, wide-bandgap, ultralow-loss integrated photonics

Authors: Yue Hu, Xue Bai, Baoqi Shi, Jiahao Sun, Yafei Ding, Zhenyuan Shang, Hanke Feng, Liping Zhou, Bingcheng Yang, Shuting Kang, Yuan Chen, Shuyi Li, Jinbao Long, Chen Shen, Fang Bo, Xin ou, Cheng Wang, Junqiu Liu

Abstract: Integrated photonics has revolutionized optical communication, sensing, and computation, offering miniaturized and lightweight solutions for spacecraft with limited size and payload. Novel chip-scale instruments based on ultralow-loss integrated photonic platforms, including lasers, frequency combs and atomic traps, have been developed for space applications. Therefore, quantifying the space compa… ▽ More Integrated photonics has revolutionized optical communication, sensing, and computation, offering miniaturized and lightweight solutions for spacecraft with limited size and payload. Novel chip-scale instruments based on ultralow-loss integrated photonic platforms, including lasers, frequency combs and atomic traps, have been developed for space applications. Therefore, quantifying the space compatibility of ultralow-loss photonic integrated circuits (PICs), particularly their radiation resistance, is critical. This study experimentally evaluates the radiation resistance of ultralow-loss Si$_3$N$_4$, 4H-SiC, and LiNbO$_3$ PICs under intense $γ$-ray and high-energy proton irradiation. Results show that proton irradiation with $1.1 \times 10^{10}$ $\mathrm{p/cm^2}$ total flux does not significantly increase optical loss or alter the refractive index of these PICs, while $γ$-ray irradiation with 1.2 Mrad accumulated dose only marginally increases their optical loss. These findings provide preliminary evidence of the excellent space compatibility of ultralow-loss Si$_3$N$_4$, 4H-SiC, and LiNbO$_3$ PICs, highlighting their potential for compact and lightweight space systems. △ Less

Submitted 4 March, 2025; originally announced March 2025.

Comments: 10 pages, 5 figures