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Physics Physics Atomic Physics

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Thursday 20 August

Atomic Physics · Cross-listed from quant-ph

Nonthermal Dynamics of a One-dimensional Rydberg-atom Chain with Constraint Four-body Interactions

Tianyi Yan and Weibin Li

We investigate dynamics of a linear chain of Rydberg atoms driven by a constrained four-body interaction, where two neighboring atoms are excited simultaneously from the electronic ground state $|0\rangle$ to Rydberg state $|1\rangle$ only when their closest neighbors are in $|0\rangle$ state. By employing an ansatz for the many-body ground state, the low-energy Hamiltonian is given by a tridiagonal form. The many-body ground state energy, which scales linearly with the chain length $L$, is obtained analytically in the thermodynamic limit and agrees with the one of the exact diagonalization. Our model supports quantum many-body scar eigenstates that are nearly equally spaced energetically. The scar states overlap strongly with the basis state $|\mathbf{0}\rangle=|0\cdots 0\rangle$. We show that the overlap distribution is tilted by the state-dependent four-body interaction. This leads to non-ergodic dynamics, evidenced by the revival of the initial state. The four-body constrained model can be realized with Rydberg atoms in a Peierls array with alternating bond lengths, where atoms on the shorter and longer bonds experience Rydberg blockade and antiblockade, respectively. Our study provides a pathway to explore constrained non-ergodic dynamics with four-body interactions by combining the Rydberg blockade and antiblockade.
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Atomic Physics · Cross-listed from quant-ph

Lensing and enhanced single atom detection via a single-pixel nanostructure

Ling-Xiao Wang, Lei Xu, Ai-Ping Liu et al. (+7 more)

We propose and demonstrate a general mechanism for nanoscale lensing based on the phase gradient imposed by a single nanostructure scattering light in its near-field. We verify this effect using an optical waveguide on a substrate, with single atoms serving as quantum probes that sample the near-field intensity through their fluorescence. This quantum probing technique provides a unique, non-destructive approach to characterizing focused optical fields and reveals a 4-fold enhancement in single atom detection efficiency. This work establishes on-chip nanostructures as a multi-functional quantum optics platform that can efficiently route photons, localize fields, and enhance atom-photon coupling, offering new opportunities for trapping and manipulating single atoms and realizing hybrid nanophotonic-atomic systems for quantum applications.
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All authors Ling-Xiao Wang, Lei Xu, Ai-Ping Liu, Guang-Jie Chen, Yuan-Hao Yang, Jia-Qi Wang, Xin-Biao Xu, Guang-Can Guo, Chang-Ling Zou, Guo-Yong Xiang

Wednesday 19 August

Atomic Physics · Cross-listed from quant-ph

Multipolar Light-Matter Hamiltonians in Symmetry-Breaking Photonic Vacuums

Liu Yang, Jiadu Lin and Qing-Dong Jiang

We show that the conventional multipolar Hamiltonian is qualitatively modified when the photonic vacuum breaks inversion or time-reversal symmetry. By explicitly applying the Power-Zienau-Woolley transformation, we derive the resulting multipolar Hamiltonians for two idealized chiral photonic environments: a spatial-chiral vacuum, which breaks inversion symmetry, and a temporal-chiral vacuum, which breaks time-reversal symmetry. In the spatial-chiral case, the transformation generates an inversion-breaking self-energy, whereas in the temporal-chiral case it produces an additional Zeeman-like energy. Using a trapped hydrogen-like atom and a charged harmonic oscillator in cavities as minimal examples, we show that these symmetry-dependent terms lead to characteristic spectral shifts. Our work provides a general framework for describing light-matter interactions in chiral quantum electrodynamics and identifying the associated symmetry-dependent effects on cavity-embedded atoms, molecules, and quantum materials.
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Atomic Physics · Cross-listed from quant-ph

Thermal Throttling of Quantum State Transfer

Twesh Upadhyaya, T. C. Mooney, Yifan Hong et al. (+1 more)

Quantum state transfer on qubit lattices is a crucial step in a panoply of quantum information processing tasks. Understanding its fundamental limits in the presence of practical imperfections remains a pressing open question. In particular, it is unclear how thermal noise in the intermediate ancilla sites impedes transfer. In this work, we derive tight lower bounds on the necessary growth of commutator norms to achieve approximate state transfer. Specializing to 1D power-law systems with thermal ancilla states, we demonstrate that state transfer runtimes depend sensitively on the scaling of temperature with system size, improving logarithmic bounds to algebraic ones. Our work extends previous results on exact state transfer to the qualitatively different and more practically relevant regime of approximate state transfer.
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All authors Twesh Upadhyaya, T. C. Mooney, Yifan Hong, Alexey V. Gorshkov

Atomic Physics · Cross-listed from cond-mat.quant-gas

Electrostriction in a Bose-Einstein Condensate of Dipolar Molecules

Haneul Kwak, Ian Stevenson, Weijun Yuan et al. (+5 more)

The recent creation of a Bose-Einstein condensate (BEC) of dipolar molecules has opened a new frontier for many-body quantum systems in which dipolar interactions can drive novel self-organization phenomena. Here, we observe electrostriction in a molecular BEC, an elliptical deformation driven by anisotropic dipolar interactions. We use double microwave dressing, involving $\sigma$- and $\pi$-polarized fields, to control non-axially symmetric dipolar interactions. We compare the experimental observations of electrostriction to a model based on an extended Gross-Pitaevskii equation and find excellent agreement in the regime of weak to moderate interactions. Using electrostriction, we demonstrate that the molecular BEC can be torqued by dynamically changing the orientation of the elliptical $\sigma$ microwave field. This provides a route to setting molecular quantum gases into rotation, opening opportunities to probe vorticity, superfluidity, and supersolidity in strongly dipolar matter.
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All authors Haneul Kwak, Ian Stevenson, Weijun Yuan, Siwei Zhang, Asaf Toprakci, Lin Su, Tijs Karman, Sebastian Will

Atomic Physics · Cross-listed from physics.optics

Transversality Locks Longitudinal Gradients in Structured-Light Quadrupole Transitions

Kayn A. Forbes, Dale Green, Abdullah F. Alharbi et al. (+1 more)

Electric quadrupole absorption is driven by optical field gradients, not by field amplitudes alone. This distinction is crucial for structured light, where a paraxially small longitudinal field can generate a leading-order longitudinal gradient. For fully vectorial Laguerre-Gaussian modes, Maxwell transversality locks this longitudinal gradient to the transverse structured gradient of the leading paraxial field. This locking is therefore a general electromagnetic constraint, not a focusing-dependent correction that can be removed independently. Decomposing the symmetric-traceless optical field-gradient tensor into spherical components reveals a strongly channel-selective response: the $\Delta m=0$ transition requires the longitudinal gradient at the retained order, the $\Delta m=\pm1$ channels receive scalar and vectorial nonparaxial corrections on top of the carrier-scale longitudinal derivative of the transverse field, and the $\Delta m=\pm2$ channels remain transverse at the same order. These results show that longitudinal optical structure can enter structured-light quadrupole transitions as an indispensable leading-gradient contribution, even when the longitudinal field amplitude itself is paraxially small.
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All authors Kayn A. Forbes, Dale Green, Abdullah F. Alharbi, Akbar Salam

Atomic Physics · Cross-listed from physics.optics

3D trapping of a meta-atom in an intensity minimum

Bin Lu, Adeel Afridi, Nadine Meyer et al. (+1 more)

High-refractive-index particles have recently attracted a growing interest in optical levitation experiments, offering the ability to further engineer optical forces through electromagnetic Mie resonances. Unlike standard silica particles, which are predominantly trapped in the dipole regime and exhibit trap frequencies mainly determined by material density, resonant meta-atoms formed by high-index particles enable qualitatively new trapping behaviors. In this work, we experimentally investigate the trapping of resonant silicon particles in an optical standing wave. A direct comparison of silicon and silica highlights the fundamental differences in their optical force scaling and trapping dynamics. Beyond conventional trapping at intensity-maxima, we demonstrate deterministic and stable three-dimensional trapping of silicon nanoparticles in optical intensity minima, a regime that remains inaccessible for silica particles. Drawing a mesoscopic analogy with blue-detuned atom trapping, our results establish meta-atoms as a versatile approach to further extend the optical manipulation tool box towards accessing novel trapping regimes e.g. in close proximity to a surface.
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All authors Bin Lu, Adeel Afridi, Nadine Meyer, Romain Quidant

Atomic Physics · Cross-listed from quant-ph

Quantum-Enhanced Atomic Sensor via Spin Nonequilibrium Criticality

Ding Huang, Minwei Shi, Guzhi Bao et al. (+2 more)

The sensitivity of quantum sensors is fundamentally constrained by the standard quantum limit (SQL) arising from intrinsic quantum fluctuations. While non-classical resources like squeezing or entanglement can surpass this limit, their utility is often restricted by the extreme fragility of entangled states and the complexity of their preparation. Quantum criticality offers a compelling alternative by harnessing divergent susceptibility to amplify signals without requiring fragile non-classical resources. However, the practical benefit of this approach has remained controversial due to the potential for the simultaneous amplification of quantum noise. Here, we demonstrate a universal protocol for noiseless critical sensing by engineering a light-driven atomic ensemble near a dynamical critical point. Analogous to a Kapitza pendulum near its inverted orientation, the spin system enters a non-equilibrium regime where the signal susceptibility diverges while the quantum noise periodically recedes to its coherent baseline. We exploit this “noise ebbing” to create a built-in noiseless amplifier, demonstrating a 3.3 dB metrological gain over the SQL in an atomic magnetometer. Our implementation exhibits intrinsic robustness against common experimental imperfections such as detection losses, establishing non-equilibrium critical dynamics as a practical and versatile paradigm for surpassing the fundamental limits of quantum sensing.
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All authors Ding Huang, Minwei Shi, Guzhi Bao, Keye Zhang, Weiping Zhang

Atomic Physics

$Ab$ $initio$ calculation of hyperfine-structure properties to extract nuclear magnetic octupole moments of $^{69}$Ga and $^{71}$Ga

Fei-Chen Li and Yong-Bo Tang

We calculate the hyperfine-structure properties of the low-lying states in $^{69}$Ga and $^{71}$Ga using the relativistic coupled-cluster method at the singles and doubles (RCCSD) level. The properties include the first-order hyperfine constants and the second-order corrections arising from off-diagonal hyperfine interactions. Based on our theoretical results, we reanalyze the previous hyperfine-splitting measurements of the $4p_{3/2}$ state in $^{69,71}$Ga [R. T. Daly and J. H. Holloway, Phys. Rev. 96, 539 (1954)], and refine the nuclear magnetic octupole moments of these two isotopes. The refined values $\Omega(^{69}\mathrm{Ga})=0.123(9)\,\mu_N\times b $ and $\Omega(^{71}\mathrm{Ga})=0.165(15)\,\mu_N\times b $ are about 13% and 12% larger than the earlier results reported by Daly and Holloway. By providing the first independent ab initio determination, the present results offer a reliable set of reference values for the magnetic octupole moments of $^{69,71}$Ga, which will benefit both future high-precision measurements and nuclear-structure calculations.
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Atomic Physics

Electron Correlation Enables Phase-Coherent One-Attosecond Pulse Trains

Andrés Marchisio, Isobel McSweeney, Paraskevas Tzallas et al. (+2 more)

Attosecond synthesis is ultimately a phase problem: a broad spectrum produces an ultrashort waveform only if its harmonics remain phase-locked. We show theoretically that correlated two-electron high-harmonic generation in helium driven by a long, multicycle laser pulse supports a train of soft-x-ray bursts with durations approaching 1 as. Using a two-electron strong-field approximation, we calculate the complex harmonic spectrum and reconstruct the temporal emission while retaining its full intrinsic spectral phase, rather than imposing a flat-phase approximation. Despite the trajectory-dependent phase accumulated by two continuum electrons, the correlation-extended plateau contains a broad phase-coherent region reaching the keV range. Its superposition produces reproducible bursts separated by one half-cycle of the driving field. These results identify electron correlation not only as a mechanism for extending the high-harmonic cutoff, but also as a route toward phase-coherent x-ray waveforms on the zeptosecond timescale.
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All authors Andrés Marchisio, Isobel McSweeney, Paraskevas Tzallas, Maciej Lewenstein, Marcelo F. Ciappina

Atomic Physics · Cross-listed from hep-ex

Technical Proposal for the Atom Interferometer CERN Experiment (AICE) Facility

Gianluigi Arduini, Nadja Augst, Mark G. Bason et al. (+79 more)

We present the technical proposal for the Atom Interferometer CERN Experiment (AICE), a $\mathcal{O}(100)$ m vertical atom interferometer to be installed against the wall of the PX46 access shaft to the LHC. AICE is conceived as a versatile and flexible long-baseline atom-interferometry facility whose primary scientific goal is probing for bosonic ultralight dark matter (ULDM) in a mass range inaccessible to other experiments, with a secondary goal of pioneering the exploration of gravitational waves (GWs) with frequencies in the range ${\sim}$0.03-3 Hz as a pathfinder for future longer-baseline detectors. The initial configuration employs ultracold $^{87}$Sr atoms in a single-photon 698-nm interferometer with three shaft-based atom sources in a multi-source gradiometer geometry, supported by one surface reference source for laser stabilisation and diagnostics, to target scalar ULDM. Operation with $^{88}$Sr will give sensitivity to axion-like particles (ALPs), vector ULDM with $B-L$ couplings and violation of the principle of equivalence, while a $^{171}$Yb upgrade will improve the sensitivity to $B-L$ couplings and equivalence violations. Probing the Einstein equivalence principle (EP) and measuring $\alpha$ will proceed in parallel with the ULDM searches. A conceptual feasibility study and a detailed technical implementation study have established that PX46 is a uniquely mature and implementation-ready site, with no technical showstoppers. Completing site preparation works during LS3 would enable the subsequent installation and operation of AICE without impacting HL-LHC operations. The detector design builds on the VLBAI and MAGIS experiments and the AION-10 Technical Design Report, scaling the strontium gradiometer architecture to the $\sim$100 m baseline. AICE is endorsed by the TVLBAI Proto-Collaboration, comprising 57 institutions in 22 countries.
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All authors Gianluigi Arduini, Nadja Augst, Mark G. Bason, Charles Baynham, Andrea Bertoldi, Gianfranco Bertone, Diego Blas, Daniela Bortoletto, Sougato Bose, Roberto Ales Bozzi, Oliver Buchmueller, Tamara Alice Bud, Clare Burrage, Sergio Calatroni, John Carlton, Vassilis Charmandaris, Maria Luisa Chiofalo, Pierre Cladé, Jonathon Coleman, Fabio Corsanego, Albert De Roeck, Arnaud Devienne, Fabio Di Pumpo, John Ellis, Pierre Fayet, Chris Foot, Elina Fuchs, Naceur Gaaloul, Susan Gardner, Enno Giese, Eduardo Granados, Saïda Guellati-Khelifa, Michael Guinchard, Timo Hakulinen, Tiffany Harte, Richard Hobson, Michael Holynski, Angelo Infantino, Alex Kehagias, Eva Kilian-Rademacher, Wolfgang Korsch, Damien Lafarge, Samuel Lellouch, Lucas Lombriser, Elias Lopez Asamar, J. Luis Lopez-Gonzalez, Michele Maggiore, Charline Marcel, Anna Marchant, Christopher McCabe, Gaetano Mileti, Peter Millington, Jeremiah Mitchell, Noam Mouelle, Angel Navascues Cornago, François Pillon, Rosa Poggiani, Johann Rafelski, Ernst M. Rasel, Maike Reckermann, Albert Roura, Rui Samoes, Federico Sanchez Nieto, Jack Sander, Carlo Scarcia, Jesse Schelfhout, Wolfgang Schleich, Dennis Schlippert, Ulrich Schneider, Steven Schramm, Florian Schreck, Olga Sergijenko, Marcelle Soares-Santos, Guglielmo M. Tino, Jonathan N. Tinsley, Tristan Valenzuela, Daniel Valuch, Maurits van der Grinten, Klaasjan van Druten, Ville Vaskonen, Wolf von Klitzing, Michael Werner

Atomic Physics

Comparative study of nonperturbative electron-positron pair production by intense laser fields colliding with either bremsstrahlung $\gamma$-rays or relativistic ions

S. Remme, A. B. Voitkiv, S. Villalba-Chávez et al. (+1 more)

It is well known that electron-positron pairs can be created in the strong-field environments formed by (i) a high-intensity laser field and a high-energy $\gamma$-photon (nonlinear Breit-Wheeler process) or (ii) a high-intensity laser field and a nuclear Coulomb field (nonlinear Bethe-Heitler process). Both of these processes are particularly interesting in the interaction regime where the laser field enters nonperturbatively. Various experimental collaborations are currently aiming at detecting for the first time the nonperturbative Breit-Wheeler process, by exploiting high-intensity laser pulses and $\gamma$-ray sources based on bremsstrahlung. In contrast, an experimental observation of the nonlinear, nonperturbative Bethe-Heitler process still lies further ahead in the future because its technical realization appears at present more challenging. Our comparative study shows, however, that the physical properties of the total rates for the processes (i) and (ii) can become remarkably similar when the parameters for the bremsstrahlung-driven nonperturbative Breit-Wheeler process are properly chosen. In this sense, the upcoming experiments on the nonlinear Breit-Wheeler process could also be used to closely “simulate” the currently hard to observe nonlinear Bethe-Heitler process.
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All authors S. Remme, A. B. Voitkiv, S. Villalba-Chávez, C. Müller

Tuesday 18 August

Atomic Physics

Artifact side peaks in saturated absorption spectroscopy caused by inappropriate lock-in amplification

Leo Matsuoka

Saturated absorption spectroscopy is a powerful technique that provides valuable information about gas-phase atomic targets, including not only the precise positions of transitions but also the effects of velocity-changing collisions, which manifest as changes in the shape of the peaks. However, using a lock-in amplifier inappropriately can generate artifact side peaks, potentially leading to a misinterpretation of results. To investigate the emergence of these artifacts, we conducted numerical calculations based on the basic Lambert-Beer's law. Our model reproduced the artifact side peaks and revealed that these artifacts become more significant as the transmittance of the probe laser decreases.
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Atomic Physics

Directional Hydrogen Migration in Acetonitrile Dication in Asymmetric Ultrashort Intense Laser Fields

Sato Miyasaka, Yuki Ono, Hiroka Hasegawa et al. (+3 more)

We investigate intramolecular hydrogen migration in acetonitrile dication in phase-controlled $\omega$-$2\omega$ intense laser fields (800 and 400 nm, 3.3$\times$10$^{14}$ W/cm$^2$) using three-dimensional coincidence ion momentum imaging. The two-body Coulomb explosion pathway, CH$_3$CN$^{2+}$ $\rightarrow$ CH$_3^+$ + CN$^+$, exhibits a clear phase-dependent fragment asymmetry along the laser polarization direction, showing that the tunnel ionization preferentially prepares the acetonitrile dication with the methyl group pointing toward the smaller amplitude side of the laser electric fields. The Coulomb explosion pathway occurring after the migration of a single hydrogen atom, CH$_3$CN$^{2+}$ $\rightarrow$ CH$_2^+$ + HCN$^+$, shows a pronounced reduction in the fragment asymmetry. A clear deuteration effect observed for the asymmetry of the hydrogen-migration pathway suggests that the two-color asymmetric laser field has a significant impact on directionality of intramolecular hydrogen migration in acetonitrile dication.
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All authors Sato Miyasaka, Yuki Ono, Hiroka Hasegawa, Runa Kuroda, Akitaka Matsuda, Akiyoshi Hishikawa

Atomic Physics

Probing the electroweak structure of nuclei with rare atoms and molecules

Silviu-Marian Udrescu, Antoine Belley, Jason D. Holt et al. (+2 more)

Precision experiments of atoms and molecules have become a powerful probe of the electroweak structure of atomic nuclei and of physics beyond the Standard Model. We review how the interaction between a nucleus and its surrounding bound electrons can be exploited to precisely measure the electromagnetic, parity-violating, and CP-violating properties of nuclei and their fundamental constituents. We focus on rare, unstable isotopes, surveying the experimental techniques and facilities developed in recent years that have extended these measurements to the most exotic regions of the nuclear chart. Recent advances in the precision control and interrogation of single molecules, together with direct laser excitation of nuclear transitions, are opening new frontiers in nuclear and particle physics. At the same time, progress in nuclear theory, machine learning, and high-performance computing is strengthening the connection between our microscopic description of nature and laboratory observables. In many cases, the precision with which nuclear and particle physics properties can be extracted is now limited not by experiment, but by the molecular, atomic, or nuclear theory required to interpret the measurements. This challenge presents a major opportunity for combined theoretical and experimental advances that will enable future discoveries.
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All authors Silviu-Marian Udrescu, Antoine Belley, Jason D. Holt, Gilad Perez, Ronald F. Garcia Ruiz

Atomic Physics

Ultrafast and high resolution spatial light modulation for cold atoms

Alexander Dennisovich Deters, Yanfei Li, Alexander Douglas et al. (+2 more)

Programmable arrays of ultracold atoms are a leading platform for quantum computation and simulation, enabling state-of-the-art implementations of quantum error correction, and analog simulations of Hubbard models that address open problems in condensed matter physics. In these systems, all local control is mediated through precisely shaped optical fields, and so the challenge of managing many-body quantum states becomes an exercise in optical design. In particular, one wishes for fast, flexible control with low disorder and heating, and access to large arrays with many atoms. An ideal optical system therefore must generate arbitrary patterns with high spatial resolution and low disorder, and alter these patterns on a timescale that is faster than the relevant atomic dynamics. Here, we present an optical system that is comparable to previous approaches in scale, while advancing all other axes. We demonstrate arbitrary pattern generation with $10^{-3}$ intensity resolution, a frame rate of $>84$ MFPS (megaframes per second), and a spatial resolution of $83 \times 52$ beam waists (with $11 \times 52$ waists accessible via a single $40$ GHz electro-optic modulator). These capabilities unlock a new class of experiments. We develop and numerically validate a scheme for fully programmable Hubbard models, with time-dependent control over local chemical potentials, tunneling amplitudes, on-site interactions, and patterns of artificial magnetic flux. The same architecture performs fast, arbitrary permutations of tweezers in 2D, decoupling optical constraints from the design of high-rate error-correcting codes.
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All authors Alexander Dennisovich Deters, Yanfei Li, Alexander Douglas, Markus Greiner, Aaron W. Young

Atomic Physics · Cross-listed from quant-ph

High-Harmonicity Planar Penning Traps for Single-Electron Qubits

Kedar Mal, A. N. Agnihotri, Sugam Kumar et al. (+2 more)

We present a detailed account of the design choices required for planar Penning traps that feature a highly harmonic confining potential. High harmonicity is indispensable for a number of applications, particularly for confinement of single electrons as qubits in quantum-information processing. The present work extends previous studies [D. Goldmann and G. Gabrielse, Phys. Rev. A 81, 052335 (2010)] by a fully analytic treatment of finite electrode gaps and their relevance for small traps on the millimetre size scale and below, when relative gap sizes are non-negligible. We derive the overall trap potential with a particular focus on different models of finite-gap potentials and show how to find the optimum trap geometry and electrode voltages to minimize anharmonicities. The analytic calculations are compared with detailed finite-element simulations.
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All authors Kedar Mal, A. N. Agnihotri, Sugam Kumar, Wolfgang Quint, Manuel Vogel

Atomic Physics

Optically Writable Atomic Vapor Memory as a Substrate for Optical Reservoir Computing

Elizabeth Robertson, Mingwei Yang, Lina Jaurigue et al. (+3 more)

We present an optical random access memory (ORAM) based on warm cesium (Cs) atomic vapor and demonstrate its operation as the physical substrate of a reservoir computer. Information is stored in the hyperfine population distribution of a Cs ensemble via optical pumping and retrieved through differential probe absorption. Spatial multiplexing via acousto-optic deflection provides eight addressable memory rails able to store up to 3.8 bits of information per rail. Employing this platform as a temporally multiplexed reservoir, we achieve a kernel rank ($\mathrm{KR}= 8.8 \pm 0.4$), and a minimum bit error rate of $0.02 \pm 0.01$ on the Exclusive-or (XOR) benchmark. We find the limited memory lifetime constrains the achievable temporal depth, encouraging further research into fast addressable memories. This constitutes the first demonstration of a free-space, optically writable atomic RAM as a substrate in an optical reservoir computing system.
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All authors Elizabeth Robertson, Mingwei Yang, Lina Jaurigue, Guillermo Gallego, Kathy Lüdge, Janik Wolters

Atomic Physics · Cross-listed from quant-ph

Single-atom detection with a quantum-controlled mechanical oscillator

Maxime Perdriat, Maciej Dziewiecki, Josef-Anton Agner et al. (+4 more)

Using supersonic expansion, we create a time-gated, directional beam of Xe atoms with a narrow momentum distribution and detect their collisions with a levitated nanosphere cooled to its quantum ground state. We observe individual momentum kicks below 50 keV/c with 96% confidence and distinguish directional momentum transfer from the atomic beam against the background of thermal collisions. Our experiments constitute a first step toward the exploration of distance-dependent short-range interactions between atoms and levitated systems, as well as toward the use of levitated platforms for impulsive force sensing in previously unexplored parameter regimes.
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All authors Maxime Perdriat, Maciej Dziewiecki, Josef-Anton Agner, Massimiliano Rossi, Frederic Merkt, Martin Frimmer, Lukas Novotny

Atomic Physics · Cross-listed from quant-ph

Irradiation-Induced Spin Bath Evolution and as-Grown Hydrogen Defects in CVD Diamond Revealed by NV-Based DEER Spectroscopy

Olga Rubinas, Jeroen Prooth, Michael Petrov et al. (+4 more)

The aim of this paper is to provide the reader with a review and current state of the art of the fabrication of high T2 coherence diamond, optimised by the use of double electron-electron resonance (DEER) spectroscopy. Using DEER, we study the formation, transformation, and annealing of paramagnetic defects in as-grown CVD diamond and after post-processing. Electron irradiation leads to the formation of an additional S = 1/2 resonance in the DEER spectrum, which we consider to be a composite X ensemble. By tracking the concentrations of X and P1 point defects during annealing from 650C to 1200C, we find that the X ensemble initially consists of a mixture of V- spins and interstitial spins, which disappear at about 650C. Vacancies migrate during annealing, forming clusters that persist to 1000C and disappear upon annealing at 1200C, contributing to the X ensemble signal. We have developed a model of the influence of the mixed spin bath on the coherence of NV centers, which includes independent couplings with P1 centers, V-, divacancies, and interstitials. Detailed DEER studies allowed us to reveal and resolve a weak signal from two additional S = 1/2 species associated with hydrogen: NVH- and consistent with a substitutional hydrogen defect, which overlaps the vacancy spectral line. Taken together, these results show that the NV-DEER method is a powerful tool for investigating paramagnetic defects in diamond with high precision and nanoscale resolution, essential for material optimisation. The achieved high T2 coherence time is consistent with the spin bath model, and the crystals reach the quality required for advanced quantum sensing applications.
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All authors Olga Rubinas, Jeroen Prooth, Michael Petrov, Remy Vandebosch, Emilie Bourgeois, David Chvatil, Milos Nesladek

Atomic Physics

Magic-wavelength matter-wave interferometry with optical clock states

Jianing Li, Swarup Das, Xinyuan Ma et al. (+4 more)

Optical clocks and atom interferometers provide complementary ways to measure time, motion and gravity. Combining these capabilities requires matter-wave beam splitters that manipulate different clock states in the same way, so that optical internal energy becomes a controlled degree of freedom rather than a source of systematic phase shifts. Here we realized a dual matter-wave interferometer operating simultaneously on the two states of the $^{88}$Sr optical clock transition, $^1S_0$ and $^3P_0$. The interferometer is driven by Bragg pulses at the 813 nm magic wavelength, for which the two clock states experience the same optical coupling strength. This realizes a common matter-wave beam splitter for atoms whose internal energies differ by an optical excitation. With a sensitivity of 30 mrad, our measurement is consistent with a zero differential phase shift between the two clock-state Mach-Zehnder interferometers, translating to an absence of state-dependent acceleration in free fall at the level of $10^{-5}$. We further used the same interferometer to measure state-dependent optical dipole forces and determine a tune-out wavelength of the metastable $^3P_0$ state to be 478.95(8) nm. These results establish magic-wavelength clock-state interferometry as a platform for differential force sensing, excited-state polarizability metrology and future quantum-clock tests of gravity.
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All authors Jianing Li, Swarup Das, Xinyuan Ma, Thomas Zanon-Willette, Shau-Yu Lan, Chang Chi Kwong, David Wilkowski

Monday 17 August

Atomic Physics · Cross-listed from quant-ph

Fast Nondestructive Readout for High-Clock-Rate Atom Array Quantum Processor

Xu-Zhao-Qiu Zeng, Chang You, Qing-Wei Wang et al. (+18 more)

Neutral-atom arrays have rapidly advanced to support thousands of qubits and execute high-fidelity logical operations. However, these processors remain severely throttled by their slowest fundamental operation: nondestructive qubit measurement, which requires milliseconds and fundamentally limits the system's clock rate. This bottleneck arises from both an inherent photon-budget dilemma—sufficient fluorescence for reliable state discrimination must be collected without excessive heating or loss—and frame-based imaging, which imposes one common exposure and decision latency on intrinsically independent, site-local measurements. Here, we overcome these limitations with a fast, nondestructive readout architecture based on real-time, site-resolved adaptive protection. By integrating continuous photon counting with a dynamic feedforward framework, we decode qubit states with sub-microsecond latency and instantly shield atoms from redundant scattering. Demonstrated in parallel across a 100-qubit reconfigurable atom array, with adaptive protection on a 25-site subarray, this dynamic decision protocol reduces the average probe time to just $15\ \mu\text{s}$. Model-free benchmarking yields a discrimination infidelity of $4.1 \times 10^{-5}$ and an atom loss of $2.1 \times 10^{-4}$, simultaneously setting new performance records for atom arrays. Exploiting this capability, we operate repeated quantum circuits at an unprecedented 1.7 kHz clock rate with atoms reused over 120 consecutive rounds—nearly sevenfold higher than the previous record—and enter the sub-millisecond cycle regime for the first time. By removing nondestructive readout as the dominant cycle-time bottleneck, this work unlocks high-clock-rate mid-circuit syndrome extraction, paving the way for high-throughput, fault-tolerant quantum computation.
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All authors Xu-Zhao-Qiu Zeng, Chang You, Qing-Wei Wang, Zi-Feng Li, Yi Ji, Dong An, Chao Yu, Jia-Rui Liu, Zi-Mo He, Jia-Rui Gu, Yuhao Mei, Hao-Wen Cheng, Yu-Chen Zhang, Rui Lin, Zhan Wu, Jun Rui, Jun Zhang, Ming-Cheng Chen, Yu-Hao Deng, Chao-Yang Lu, Jian-Wei Pan

Atomic Physics · Cross-listed from cond-mat.quant-gas

Hydrodynamization in 1D Bose gases at nonzero temperature

Jeff Leiberton and Marcos Rigol

Hydrodynamization refers to the remarkably rapid process in relativistic heavy-ion collisions by which hydrodynamic descriptions become applicable. Following the observation of analogous behavior in ultracold one-dimensional (1D) Bose gases, hydrodynamization has been conjectured to be a universal dynamical phenomenon in quantum systems following high-energy quenches. Theoretical studies in this cold-atom setting have so far been restricted to quenches from ground states. Here we study how nonzero temperatures affect hydrodynamization. Specifically, using a homogeneous 1D gas of hard-core bosons, we explore how the initial temperature affects the timescales associated with hydrodynamization and prethermalization following a Bragg-pulse quench. We find that while the hydrodynamization coherence time remains unchanged, increasing temperature shortens both the damping time of the hydrodynamization oscillations and the prethermalization time. We argue that this is mainly the result of the broadening of the initial rapidity distribution, and introduce a nonzero-temperature dephasing time defined in terms of the extent of the rapidity distribution.
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Atomic Physics · Cross-listed from quant-ph

Classical-limit formula for matrix elements between bound states of distinct one-dimensional potentials

K. Beloy

A classical-limit formula is derived for matrix elements between bound states of distinct one-dimensional potentials. We leave open the physical interpretation of the potentials, but generally envision them to be Born-Oppenheimer-type potentials with the position variable $x$ identifying with a slowly evolving degree of freedom of the system. For instance, $x$ could represent the internuclear separation in a diatomic molecule, with the potentials being potential energy curves for different electronic states. In this scenario, the matrix elements could be, e.g., conventional Franck-Condon factors. To test the derived formula, we assume functional forms for the potentials and operator that afford analytical solutions for the matrix elements. As the classical limit is approached, the computed matrix elements exhibit a clear tendency towards the classical-limit formula, providing strong validation for the formula. In future work, we anticipate using the formula to model inhomogeneous excitation spectra of atoms in one-dimensional optical lattices, with an eye towards improved optical lattice clock performance.
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Atomic Physics

Sensitivity Scaling and Limits of Cavity Enhancement in Miniaturized Optically Pumped Magnetometers

Christopher H. Kiehl, María Hernández Ruiz, Cristina Sastre Jachimska et al. (+1 more)

The sensitivity of miniaturized optically pumped magnetometers (OPMs) is limited by weak atom-light coupling, which an optical cavity can enhance. In this work, we model the photon-shot-noise-limited sensitivity of cavity-enhanced OPMs in the regime of strongly collisionally broadened optical transitions, characteristic of buffer-gas-filled miniaturized vapor cells. The cavity enhancement is benchmarked against a single-pass free-induction-decay OPM employing Faraday-rotation readout, with the probe power and detuning jointly optimized using the Cramér-Rao lower bound as a figure of merit. For a Fabry-Pérot cavity, we compare side-of-fringe, homodyne, Pound-Drever-Hall, and Faraday-rotation readout. All four yield an optimal sensitivity enhancement scaling as $\alpha\sqrt{2\mathcal{F}/\pi}$, where $\mathcal{F}$ is the cavity finesse and $0.5\leq \alpha \leq 1$ is a readout-dependent prefactor. The enhancement is maximized at critical coupling, and we quantify its degradation away from this point. We further show that, despite spin-dependent absorption associated with the ensemble's vector polarizability, near-critical coupling can be maintained throughout spin precession at arbitrary finesse by exceeding a derived probe-power threshold and increasing the atomic detuning with finesse. We also establish a limit to the maximum cavity enhancement set by vector light-shift noise.
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All authors Christopher H. Kiehl, María Hernández Ruiz, Cristina Sastre Jachimska, Morgan W. Mitchell

Atomic Physics · Cross-listed from physics.chem-ph

ChemReporter: A Framework for Curating and Exporting Large-Scale Chemical Datasets for MLIP Training

Marie Bluntzer, Jules Tilly and Christoph Brunken

Training set quality and diversity are key determinants of the reliability of machine learning interatomic potentials (MLIPs), yet using massive datasets in full is often impractical and redundant, making intelligent data selection essential. A major bottleneck, however, is the lack of infrastructure for uniformly accessing, curating, and subsampling heterogeneous large-scale chemical datasets, which differ widely in structure, metadata, and file format. We address this gap with ChemReporter, a modular, method-agnostic framework that converts arbitrary molecular and materials datasets into a unified, queryable representation and exports the results directly into MLIP-ready training data. ChemReporter operates in three decoupled stages: processing, which parses raw datasets into a partitioned Apache Parquet repository enriched with structural, physical, and chemical metadata; querying, which filters and samples this repository via a CLI or Python API using arbitrary selection criteria, from simple physical constraints to custom, user-defined strategies; and exporting, which streams the selected subset into an HDF5 file ready for direct use in modern MLIP training frameworks. Throughout this process, every exported data point remains traceable to its original source entry, and dataset exports can be reliably reproduced given the same configuration and query database version. Because data is stored in a queryable, disk-backed format, ChemReporter can process datasets far larger than available memory, allowing it to scale to billion-structure datasets on standard compute infrastructure. ChemReporter is available on GitHub and PyPI under the Apache License 2.0.
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Sunday 16 August

Atomic Physics

A scalable chip-integrated single-photon source array based on 50 individually addressable neutral atoms

Ya-Dong Hu, Tian-Yang Zhang, Dong-Qi Ma et al. (+10 more)

Scalable arrays of identical single-photon sources are a central resource for photonic quantum information processing, quantum networks and quantum metrology. Neutral atoms provide intrinsically identical emitters that can be assembled and rearranged in optical tweezers, but a many-channel fiber interface to individually trapped atoms has remained a major technical challenge. Here we demonstrate a chip-interfaced single-photon source array based on 50 individually addressable $^{87}\mathrm{Rb}$ atoms. A glass waveguide fan-out converts the \SI{5}{\micro m} pitch of the optical-tweezer array to the \SI{127}{\micro m} pitch of a commercial fiber array, mapping each atom to its own waveguide, fiber and single-photon detector. We resolve all 50 channels with an average nearest-neighbor cross-talk of $0.4\%$ and a uniform insertion loss of \SI{2.9}{dB}, and verify single-photon emission with $g^{(2)}(0)=0.29$, presently limited by detector dark counts and residual cooling-light scattering. Combining per-channel atom discrimination, rearrangement and reservoir replenishment, we prepare source subarrays of up to 24 atoms with a $93\%$ fill fraction. For small target numbers, atom loss is repaired from the reservoir at the detection-limited rate of \SI{118}{Hz}. We further fabricate a 784-channel waveguide chip, showing that the photonic interface can be extended well beyond the present number. This architecture establishes a fiber-native neutral-atom platform for larger arrays of identical single-photon sources.
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All authors Ya-Dong Hu, Tian-Yang Zhang, Dong-Qi Ma, Yi-Chen Zhang, Liang Chen, Wen-Yi Zhu, Hong-Jie Fan, Yan-Lei Zhang, Zhu-Bo Wang, Gang Li, Xi-Feng Ren, Guang-Can Guo, Chang-Ling Zou

Saturday 15 August

Atomic Physics · Cross-listed from quant-ph

Stochastic Liouville-transport theory of light-atom interaction noise in thermal atomic vapors

Shaoxin Yuan, Bin Wu, Mingyong Jing et al. (+11 more)

Atom-light interaction noise can limit thermal-vapor sensing. Existing theories often treat internal-state dynamics, finite-mode atomic motion, and stochastic renewal separately, obscuring their coupled contributions to measured noise. We develop a general stochastic Liouville-transport theory, tested against polarization-resolved resonant Cs D$_2$ spectra. Joint experiment-theory analysis identifies atom-light noise below approximately 100 kHz as transit-dominated. Ballistic motion through the finite Gaussian mode modulates both the coupling-weighted effective atom number and trajectory-dependent Rabi coupling, producing predominantly common-mode noise. Boundary renewal introduces atoms with independently sampled ground-state sublevels, generating differential population fluctuations with opposite effects on the circular channels. Under an applied longitudinal magnetic field, experiment and theory show the same qualitative nonmonotonic change in common-mode suppression, supporting Zeeman redistribution of the channel responses. The framework can analyze noise in other thermal-atom sensors, including Rydberg-atom electric-field measurements.
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All authors Shaoxin Yuan, Bin Wu, Mingyong Jing, Chaoyang Hu, Yan Peng, Tingting Li, Xingya Li, Wenguang Yang, Junyao Xie, Zongkai Liu, Hao Zhang, Linjie Zhang, Liantuan Xiao, Suotang Jia

Friday 14 August

Atomic Physics · Cross-listed from quant-ph

Analytical Theory of Higher-Order Collective Spin Interactions in Cavity Quantum Electrodynamics

Leilani Ainsworth, Chase Gomes, Joseph Prescott et al. (+5 more)

Cavity-mediated collective-spin interactions are commonly described by a quadratic one-axis twisting Hamiltonian. However, the underlying atom-light interaction naturally generates nonlinearities to arbitrary order. Here, we derive a closed-form analytical expression for the complete hierarchy of cavity-mediated collective-spin interactions. We show that the nonlinear coefficients $\chi_k$ are governed by Chebyshev polynomials, with $k$ the order of nonlinearity. This yields a universal scaling $\chi_k\propto\eta^k$ with the single-atom cooperativity $\eta$ and a description of their dependence on cavity detuning. The result provides a systematic framework for determining when higher-order nonlinearities become relevant and when the quadratic approximation breaks down. We identify experimentally relevant regimes in which higher-order terms substantially modify collective-spin dynamics, accelerating the generation of quantum correlations and quantum Fisher information, and demonstrate that finite-order expansions can accurately reproduce the full cavity-mediated evolution. Our results establish a general framework for understanding higher-order nonlinearities in cavity quantum electrodynamics and their role in collective entanglement and quantum-enhanced sensing.
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All authors Leilani Ainsworth, Chase Gomes, Joseph Prescott, Kaley Wilcox, Jack Sullivan, Esteban Teran, Manav Bilakhia, Simone Colombo

Atomic Physics

Cold-atom comagnetometry via optical control of spin states

J.-L. Zhang, W.-T. Luo, Y. A. Yang et al. (+3 more)

Atomic spin-based comagnetometers are powerful tools for precision sensing and tests of fundamental physics. Compared with the widely used gas-cell comagnetometer systems, cold-atom systems offer access to much shorter distance scales and allow implementation of {optical} quantum control techniques. However, in order to realize long spin coherence times with cold atoms, it is necessary to employ diamagnetic atoms and overcome decoherence induced by light shifts. Here we demonstrate a cold-atom comagnetometer based on the nuclear spins of $^{171}$Yb (spin-1/2) and $^{173}$Yb (spin-5/2), jointly trapped in an optical lattice. Vector light shifts are suppressed by enforcing linear polarization of the lattice, while tensor shifts in $^{173}$Yb are suppressed via the use of a Schrödinger cat state. This enables simultaneous Ramsey interferometry on both isotopes with a spin coherence time of 60 s. We achieve a magnetic noise suppression factor exceeding $3\times10^4$, and determine the ratio of nuclear magnetic moments to 4 ppm precision. Our results establish a new cold-atom platform for spin-based sensing and open pathways toward quantum-enhanced searches for physics beyond the Standard Model.
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All authors J.-L. Zhang, W.-T. Luo, Y. A. Yang, Y.-Q. Wang, T. Xia, Z.-T. Lu