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Physics Physics Atomic Physics

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Wednesday 14 October · still arriving

Atomic Physics · Cross-listed from quant-ph

Demonstration of a mobile ion-trap quantum device

Sara Alfaro, Dipesh Bhanushali, Sankarshan Choudapurkar et al. (+8 more)

Trapped-ion devices are being investigated for transportable applications, including the transfer of exotic charged particles between laboratories and the development of portable quantum technologies. To date, ion transport has been demonstrated only in magnetic (Penning) traps, whereas radiofrequency (Paul) traps are the predominant platform in quantum science. Here, we report the first transport of a few thousand ions confined in a linear Paul trap over distances of several kilometers, with transport durations of 15 and 45 min. These results establish a foundation for mobile trapped-ion quantum devices capable of operating while in motion and may enable the transport of exotic ions in Paul traps between experimental facilities.
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All authors Sara Alfaro, Dipesh Bhanushali, Sankarshan Choudapurkar, Ashwin Bhartia, Thomas Lafenthaler, Tommaso Faorlin, Yannick Weiser, Lorenz Panzl, Thomas Monz, Rainer Blatt, Giovanni Cerchiari

Atomic Physics

Fine-structure Raman interferometry with metastable barium for magnetically resilient inertial sensing

Masaki Nagamori, Hiromi Hatano, Toshiyuki Hosoya et al. (+3 more)

Atom-interferometric quantum inertial sensors are promising candidates for inertial navigation systems owing to their high sensitivity and intrinsically low drift. However, their application to next-generation inertial navigation, targeting a drift below 100 m/month, requires exceptionally stringent inertial-sensor bias stability. In conventional Raman atom interferometers based on ground-state hyperfine transitions, suppressing inertial-sensor biases arising from quadratic Zeeman shifts requires highly optimized magnetic shielding. In this work, we propose a Raman atom interferometer based on fine-structure transitions between metastable states of barium, which exhibit a quadratic Zeeman sensitivity approximately three orders of magnitude lower than that of conventional alkali-atom Raman transitions. We show that the proposed scheme increases the allowable spatial gradient of the magnetic-field magnitude by a factor of several tens, thereby relaxing the magnetic-field-control requirements from highly optimized shielding and compensation systems to standard magnetic-field-control techniques. Furthermore, we experimentally demonstrate Mach–Zehnder interference between metastable fine-structure states of barium, validating a key building block of the proposed inertial-sensing scheme.
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All authors Masaki Nagamori, Hiromi Hatano, Toshiyuki Hosoya, Yuki Miyazawa, Tomoya Sato, Mikio Kozuma

Atomic Physics

Wigner time delay in the $4d$ giant-resonance region of iodoalkanes

Anatoli S. Kheifets, Daniele Toffoli and Piero Decleva

The iodine $4d$ giant resonance provides an unusually strong and predominantly iodine-centered photoionization channel in iodoalkanes. Recent attosecond measurements by Schröder et al. [Phys. Rev. A 112, L051104 (2025)] reported pronounced, nonmonotonic, and isomer-dependent variations of the streaking-derived $4d$ photoemission delay across the molecular series. We calculate field-free molecular Eisenbud–Wigner–Smith (EWS) delays from photoionization amplitudes represented in a multicenter B-spline basis of the time-dependent density-functional theory (TDDFT). A tensor formulation is developed in which the delay for randomly oriented molecules is evaluated from the same rank-0 and rank-2 contractions that determine the cross section and anisotropy parameter. The resulting TDDFT delays of CH$_3$I, C$_2$H$_5$I, 2-iodopropane, and both calculated conformers of 1-iodopropane form a narrow bundle throughout the 90–118~eV region and closely follow atomic-I and I$^-$ reference calculations. This robustness is consistent with the similarly weak molecular dependence of the giant resonance cross section and angular distribution, but it is in marked contrast with the much larger molecular variation found by streaking experiments. The asymptotic Coulomb–laser-coupling/continuum–continuum correction is controlled mainly by the photoelectron energy and residual charge and is therefore expected to be nearly common to the iodoalkane series. This does not exclude target-specific molecular IR effects beyond the universal Coulomb term.
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Tuesday 13 October · still arriving

Atomic Physics

Photoemission study of Iodoalkanes

Maximilian Forster, Maximilian Pollanka, Sven-Joachim Paul et al. (+7 more)

Core level atomic photoionization is influenced by the molecular environment of the emitting atom. To probe this influence we used extreme ultraviolet (XUV) radiation to measure the I$\left(4d\to\varepsilon f \right)$ photoemission of four iodine substituted alkanes in the range from 60 eV to 160 eV photon energy. Using two detection angles relative to light polarization allowed us to extract and compare the asymmetry parameter of the investigated compounds. These results are in agreement with theory by Pi and Landsman (L.-W. Pi and A. Landsman, Attosecond time delay in photoionization of noble-gas and halogen atoms, Applied Sciences 8, 322 (2018)) and previous experiments by Olney et al. (T. N. Olney, G. Cooper, and C. Brion, Quantitative studies of the photoabsorption (4.5-488 ev) and photoionization (9-59.5 ev) of methyl iodide using dipole electron impact techniques, Chemical Physics 232, 211 (1998)) for iodomethane. 2-iodopropane behaves nearly identical to iodomethane, while for iodoethane and 1-iodopropane we find a distinct and consistent, energy dependant difference most prominent at around 130 eV photon energy. This further proves the influence of the chemical environment on core level photoionization. Due to the sensitivity on the exact positions of the carbon atoms and the energy dependence we hypothesise this difference is caused by intramolecular scattering of the outgoing photoelectron wave packet, causing changes in the angular distribution.
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All authors Maximilian Forster, Maximilian Pollanka, Sven-Joachim Paul, Pascal Freisinger, Christian Schröder, Robert Richter, Michele Alagia, Alessio Bruno, Stefano Stranges, Reinhard Kienberger

Atomic Physics

Information-theoretic measures of electron correlation in a double quantum dot

W. S. Nascimento, A. M. Maniero, F. V. Prudente et al. (+1 more)

In this work, we investigated how variations in spatial confinement affect the electron correlation between two electrons in a symmetric double quantum dot. In strong confinement regime, the ground-state energy can be obtained using the Hartree-Fock method neglecting the electron-electron repulsion term. Under a weaker confinement, the FCI method provides a more accurate description. Using the mutual information as a measure of correlation, we determine the confinement regions where electronic motion is uncorrelated. We conjecture that the Shannon entropy can serve as a qualitative guide to to study the electron correlation. We identified an approximately linear relationship between mutual information and relative correlation energy.
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All authors W. S. Nascimento, A. M. Maniero, F. V. Prudente, Ginette Jalbert

Atomic Physics

Theory of Sub-Doppler Spectroscopy of Alkali Metal Vapors in the Field of Counterpropagating Bichromatic Laser Beams: Probe Beam Regime

A. M. Mikhailov and D. V. Brazhnikov

Sub-Doppler resonances observed in miniature cells ($V \ll 1 cm^3$) with Rb or Cs atoms in the field of counterpropagating bichromatic laser beams are of interest for the creation of a miniature quantum frequency standard (QFS) of the optical range. However, a theory of these resonances that takes into full account the real structure of energy levels in an atom has not yet been constructed, which would make it possible to obtain explicit analytical expressions for the absorption coefficient of the medium. This paper addresses this gap using the density matrix formalism and the algebra of irreducible tensor operators. Namely, we obtained an analytical expression for the absorption coefficient of the probe beam in the presence of a more intense counterpropagating beam (pump-probe regime). Moreover, the calculations were carried out for arbitrary parameters of laser beam polarization, arbitrary angular momenta of optical dipole transitions in the atom and various relaxation processes. The constructed theory allows us to correctly take into account the simultaneous action of various nonlinear optical effects, in contrast to the simplified three-level model of the atom, and also to investigate the partial contribution of each of them to the overall observed resonant circuit. The analysis performed, in particular, made it possible to predict an increase in the amplitude of the sub-Doppler resonance when using counterpropagating light beams with opposite circular polarizations in relation to the configuration of counterpropagating beams with orthogonal linear polarizations, which is often used in practice.
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Atomic Physics

Collision inside an atom: quantum ion-atom dynamics

Arijit Das, Yufeng Wang, Marcin Welter et al. (+6 more)

Rydberg atoms occupy a central role in quantum science; their loosely bound outer electron gives rise to properties that enable quantum information processing1 or the formation of exotic molecular bonds2. Beyond these roles, they have been proposed as a neutral platform for the observation of quantum effects in collisions and reactions of the ionic core with neutral particles3, 4, a long-standing goal of ion-based chemistry and physics. However, all of the experimental results so far could be explained using a classical description of the internuclear motion5. Here we demonstrate cold collisions inside a Rydberg helium atom, achieved by merging helium Rydberg and ground-state helium beams and imaging individual scattering events. We resolve the fully quantum-coherent motion and observe matter-wave diffraction and tunnelling-driven shape resonances down to collision energies of 90 mK. In the case of identical helium nuclei, we demonstrate a new regime of identical-particle Mott interference6, where quantum statistics begin to govern the total scattering cross section. For distinct isotopes, we show the breakdown of the Born-Oppenheimer approximation and benchmark parameter-free, state-of-the-art theory. We directly measure the helium isotope ionization-energy difference to be 15.0 +/- 0.1 K. Our experiments establish Rydberg atoms as a platform for the direct observation of quantum dynamics with a general class of ions, atoms and molecules.
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All authors Arijit Das, Yufeng Wang, Marcin Welter, Karl Horn, Dawid Dąbrowski, Michał Przybytek, Julia Narevicius, Michał Tomza, Edvardas Narevicius

Atomic Physics · Cross-listed from physics.optics

A Photonic Integrated Light Generation, Control, and Delivery Engine for Creating Cold Atoms

Andrei Isichenko, Calisto Ruiz, Chuan Zhong et al. (+7 more)

The creation of cold atoms underpins quantum sensing and precision metrology, computing, timekeeping, and fundamental science experiments. Miniaturizing the lasers and optical infrastructure, which occupy over 80% of the volume of these experiments, through photonic integration could improve robustness, reliability, and manufacturability while reducing cost and enabling portable space-based precision measurements and quantum tools for non-experts. Yet, there has been limited progress towards integration of the laser and optical infrastructure required to generate cold atoms onto a single chip. We demonstrate a photonic engine that generates, controls, and delivers precision light to create cold atoms in a rubidium 3-dimensional magneto-optical trap (3D-MOT). We integrate on a single chip two frequency-agile self-injection-locked lasers, laser frequency and intensity control, passive beam combining and splitting, signal monitoring, and high-efficiency beam delivery to a rubidium vapor cell. The integrated engine is shown to support multiple functions required for generating cold atoms including stable generation of low-noise cooling and repump light, frequency control for atom spectroscopy and stabilization, real-time laser monitoring, routing for laser offset locking, optical power modulation, and large-area three-beam delivery of 3 mW to the physics package. Fully electrically controlled, the engine enables sustained 3D-MOT operation, trapping more than 1 million atoms at an average temperature of 350 uK and supporting atom-number and temperature measurements. These results demonstrate the first single-chip integration of light generation, control, and delivery for cold-atom generation, offering a path toward smaller, more robust, and manufacturable cold-atom systems for applications including cold-atom clocks and sensors.
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All authors Andrei Isichenko, Calisto Ruiz, Chuan Zhong, Nick Montifiore, Sam J. Harding, Meiting Song, Chenghang Liu, Nitin Indukuri, Karl D. Nelson, Daniel J. Blumenthal

Atomic Physics · Cross-listed from quant-ph

Fast charging of quantum batteries assisted by nonlinear couplings

Y.-J. Shen, Y.-C. Shen, C.-H. Chu et al. (+1 more)

Charger-mediated quantum batteries offer promising opportunities for efficient energy transfer and storage at the quantum level, with potential advantages beyond their classical counterparts. Here, we theoretically demonstrate that nonlinear charger-battery interactions can substantially accelerate the charging of quantum batteries. In the weak-driving regime, sufficiently strong nonlinear coupling can dominate over the effect of dephasing and significantly reduce the charging time. In the strong- and optimal-driving regimes, where the optimal driving strength maximizes the steady-state ergotropy in the linear-coupling regime, nonlinear coupling gives rise to a new optimum in the charging time beyond that of the linear-coupling regime, accompanied by nearly critically damped dynamics. Remarkably, even in the absence of external driving, nonlinear coupling alone can substantially reduce the charging time, providing an alternative route toward fast battery charging. Our results establish nonlinear charger-battery coupling as an effective resource for accelerating quantum-battery charging and broaden the scope of interaction-enabled quantum advantages in energy transfer and storage.
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All authors Y.-J. Shen, Y.-C. Shen, C.-H. Chu, H. H. Jen

Monday 12 October

Atomic Physics

An Aubry-André localized optical lattice clock

Shuo Ma, Anke Stöltzel, Bennett Christensen et al. (+5 more)

Optical lattice clocks in space could improve satellite navigation systems and enable new tests of fundamental physics, including gravitational-wave detection and tests of relativity. In microgravity, atoms can tunnel to degenerate neighboring lattice sites, broadening the clock transition and limiting coherence times. We demonstrate Aubry-André localization in a bichromatic optical lattice formed by two magic-wavelength lasers, suppressing tunneling in a horizontal lattice clock emulating free fall. We recover a Fourier-limited clock Rabi spectrum and measure Ramsey coherence times of up to 2 s in shallow lattices, with up to 100-fold improvement over the delocalized regime. These results establish Aubry-André localization as a practical route to controlling tunneling in future space-based clocks, and open a path to operating terrestrial clocks at shallower lattice depths.
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All authors Shuo Ma, Anke Stöltzel, Bennett Christensen, Zhuoli Ding, Dhruva Ganapathy, Andrew Householder, Genyue Liu, Shimon Kolkowitz

Atomic Physics

Cavity-modified static polarizabilities of atoms and small molecules within QED full configuration interaction

T. Zalialiutdinov and D. Solovyev

Static dipole polarizabilities of H$_2$, LiH, and helium confined in a single-mode optical cavity are computed using quantum-electrodynamical full configuration interaction (QED-FCI). Response properties are obtained as finite-field derivatives of the coupled electron-photon energy. The cavity-induced modification is found to arise from the competition of two contributions of opposite sign, the dipole self-energy and photon exchange, whose relative strength depends on both the cavity frequency and the number of photons involved in the exchange. The residual change suppresses the response of the molecular ground electronic states. For the metastable states of helium atom this balance changes qualitatively, and the differential response of the $2\,^3S_1 \to 2\,^1S_0$ clock transition, which governs its sensitivity to static electric fields and to thermal radiation, is strongly enhanced instead. Cavity confinement can therefore either reduce or increase the dc Stark and blackbody-radiation shifts of a frequency standard, depending on the electronic structure of the states involved. The reported data serve as a reference for cavity-modified response and underscore the need for an exact treatment of light-matter correlation in cavity-QED predictions.
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Atomic Physics

Kinematic saturation of the electromagnetically-induced-transparency peak in thermal atomic vapors

Sheng-Xian Xiao, Jing-Yi Mao and Tao Wang

We demonstrate that, in thermal atomic vapors, the electromagnetically-induced-transparency (EIT) transmission peak exhibits saturation. Investigating the amplitude of the velocity-selected double-resonance transmission peak-a purely kinematic effect arising from finite wavevector mismatch-we identify a threshold atomic column density Ns. For column densities N below Ns, the amplitude of the transmission peak maximum increases with column density. Once it exceeds Ns, the peak amplitude maximum remains constant, while the corresponding detuning shifts away from resonance and scales as the square root of ln(N over Ns). Furthermore, We find that the operating point for optimum photon-shot-noise-limited sensitivity deviates from that of the transmission peak maximum. Our study provides guidance for optimizing EIT readout in vapor cell and for precision measurements built upon this scheme.
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Atomic Physics

Quantum tomography of bright squeezed vacuum via strong-field ionization

Peizeng Li, Xiaoxiao Long, Haodong Liu et al. (+4 more)

Strong-field physics uses intense optical fields to probe and control electron motion on ultrafast timescales. Recent advances in bright squeezed vacuum have brought macroscopic quantum states of light into the ultrafast strong-field regime, opening prospects for high-harmonic generation and photoionization. Yet linking its phase-space structure to subcycle electron dynamics remains challenging. Here, we demonstrate strong-field tunneling ionization of xenon using a phase-referenced combination of coherent and squeezed fields, with the coherent field defining the ionization clock and quadrature fluctuations of the zero-mean squeezed field providing control. The squeezed field selectively modulates atomic tunneling barriers and electron wave packets, imprinting signatures on photoelectron momentum distributions, number statistics, and energy spectra. Using coincidence measurements of photon number and phase-sensitive photoelectron momentum distributions, we perform quantum state tomography of the driving field by reconstructing its Wigner function. These results establish a bidirectional interface between quantum optics and nonperturbative strong-field electron dynamics, in which the driving quantum field shapes subcycle electron motion while photoionization provides a phase-sensitive probe of the field's quantum state. This work opens new routes toward controlling electron dynamics with quantum light and phase-sensitive quantum state metrology through ultrafast strong-field electron dynamics.
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All authors Peizeng Li, Xiaoxiao Long, Haodong Liu, Xi Li, Yongkai Deng, Chuan Cheng, Yunquan Liu

Sunday 11 October

Atomic Physics · Cross-listed from physics.optics

Photon-efficient readout of optical cavity arrays via spatial heterodyne

Bridger McGimpsey and Matt Jaffe

Optical cavity arrays are an emerging tool for efficiently interfacing optical photons to quantum emitters for applications such as quantum computing. In this work, we demonstrate a metrology technique for such cavity arrays by interfering cavity array outputs against a tilted reference beam on a camera, constituting a spatial heterodyne. Both the amplitude and phase of each cavity's transmitted field can be extracted from the resulting images. Enabled by the improved scaling of heterodyne detection over intensity detection in the presence of technical noise, we demonstrate signal-to-noise ratio greater than one down to the single detected photon level, even in the presence of hundreds of noise equivalent photons. This readout technique holds promise for fast, non-destructive imaging of atomic qubits in cavity arrays by requiring fewer scattered photons while allowing the use of fast cameras with higher electronic readout noise.
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Atomic Physics

Proposal for a multi-ion optical clock with hundreds of ions

Pavel Kamenskikh, Vasiliy Smirnov, Ilya Gerasin et al. (+2 more)

Scaling trapped-ion optical clocks to hundreds of ions remains a major challenge due to inhomogeneous frequency shifts in large ion crystals. Here, we propose a circular surface-trap architecture for a multi-ion optical clock with hundreds of ions. The rotational symmetry of the ion crystal suppresses the main sources of inhomogeneity, quadrupole shift.We investigate the feasibility of a clock based on a ring crystal of 400 $^{40}\mathrm{Ca}^{+}$ ions and propose a suitable experimental setup configuration. We have shown that circular configuration of ions leads to suppression by two orders of magnitude of the quadrupole shift comparing to the linear trap. Combined with stray-field compensation and dynamical decoupling techniques, this architecture provides a pathway toward multi-ion optical clocks with fractional frequency uncertainty at the $10^{-18}$ level and an expected 20-fold improvement in frequency stability compared to single ion clocks.
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All authors Pavel Kamenskikh, Vasiliy Smirnov, Ilya Gerasin, Ilya Semerikov, Wei Zhang

Atomic Physics · Cross-listed from cs.IT

Rydberg Atomic Quantum Receivers for OFDM Systems: An Atomic-Comb Design

Yuanbin Chen, Chong Meng Samson See and Chau Yuen

Rydberg atomic quantum receivers (RAQR) exhibit exceptional sensitivity to radio-frequency (RF) signals, positioning them as promising candidates for next-generation wireless systems. Extending their capabilities to orthogonal frequency-division multiplexing (OFDM), however, requires atomic responses that go beyond broadband reception and are tailored to the structured interference of multicarrier signals. To bridge this gap, we develop an atomic-comb Rydberg receiver based on six-wave mixing (SWM) transduction. In particular, injecting a multi-tone local oscillator (LO) into the RAQR generates frequency-shifted replicas of the intrinsic SWM response. By subtly tuning the amplitude and phase of each LO tone, constructive and destructive interference can be selectively induced to preserve desired response components while attenuating harmful frequency offsets. Furthermore, we harness the response-reshaping capability of the proposed atomic comb to proactively mitigate OFDM interference. More explicitly, by exploiting the discrete difference-frequency structure of both carrier-frequency-offset (CFO)-induced and phase-noise (PN)-induced inter-carrier interference (ICI), we optimize the atomic-comb response to suppress dominant ICI components directly. We further reveal an intrinsic coupling between spectral shaping and the time-domain effective channel memory, motivating a joint optimization of both ICI and inter-symbol interference (ISI), which simultaneously suppresses inter-carrier leakage and post-cyclic-prefix (CP) tail energy. Extensive simulation results validate our atomic-comb design, unveiling that the proposed atomic comb can effectively reshape the receiver response over the OFDM, while mitigating ICI, shortening the effective channel memory, and substantially lowering CP overhead.
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Atomic Physics · Cross-listed from cond-mat.mes-hall

Valley-resolved high harmonics probe symmetry breaking beyond the Dirac cone

Pablo Pais, Alfredo Iorio and Marcelo F. Ciappina

Low-energy electrons in graphene obey an emergent, rotationally invariant Dirac equation, while the honeycomb lattice enters only through higher-order, symmetry-breaking corrections, the leading one being trigonal warping. This provides a unique solid-state arena to address a cornerstone challenge in quantum gravity: how to detect ultraviolet symmetry-breaking granular corrections, suppressed by a fundamental scale, atop an emergent infrared relativistic continuum. We show that intense counter-rotating $\omega$-$2\omega$ fields and valley-resolved high-harmonic generation (HHG) provide such a probe. Within a family of models that interpolates continuously between the isotropic Dirac cone and nearest-neighbour graphene at fixed Fermi velocity, the valley contrast of the harmonic yield vanishes identically in the symmetric theory, grows linearly with the warping coupling, and its valley-even counterpart appears only at second order, as expected from effective-field-theory power counting. The stronger the laser, the farther it drives electrons from the Dirac points, so the laser intensity plays the role of the collision energy. For the fourth harmonic, the leading warping correction alone accounts for the valley contrast of real graphene up to fundamental intensities of about $10^{11}$ W/cm$^2$, below the damage threshold of monolayer graphene, whereas the fifth harmonic already reveals higher-order lattice corrections at intensities around $10^{10}$ W/cm$^2$. The two harmonics, which rotate in opposite directions, are emitted by opposite valleys. Valley-resolved harmonics are far more sensitive than the residual valley populations, making them a practical detector of lattice-scale physics hidden beneath an emergent Dirac theory.
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Saturday 10 October

Atomic Physics

Inverse identification of thermal-radiative parameters for reduced effective-temperature uncertainty in an ion optical clock

Jie Zhao, Yani Zuo, Shaoyang Dai et al. (+8 more)

The blackbody-radiation (BBR) shift remains a leading systematic uncertainty of room-temperature single-ion optical clocks. Accurate evaluation of this shift requires the effective temperature at the ion position, which is difficult because RF heating, low and spatially varying surface emissivity and inaccessible trap surfaces make this quantity difficult to measure directly. Here, we developed a hybrid inversion framework that combines radiance-domain infrared thermography, black-painted high-emissivity reference regions, a finite-element model of a 171Yb+ end-cap ion trap and a reduced-order surrogate for repeated forward calculations and parameter identification. The surrogate reproduced the FE test fields with a full-field mean absolute error (MAE) of 0.02220 mK. The calibrated model predicted the ion-position effective temperature with a combined standard uncertainty of 155.0 mK, corresponding to a temperature-related BBR frequency-shift uncertainty of 1.647 x 10^-19 for the 2S1/2-2F7/2 (467 nm) E3 transition. This method provides a reproducible route for reducing and tracing the BBR uncertainty of room-temperature trapped-ion optical clocks.
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All authors Jie Zhao, Yani Zuo, Shaoyang Dai, Chaowei Wang, Ang Huang, Jian Song, Guangyao Wang, Fangfei Wu, Haotian Shi, Zhengyong Li, Fang Fang

Atomic Physics

Interpretation of chirality imprinted on photoelectron momentum spectra by three-dimensional light fields

Junxin Yuan, Yuhong Li, Fei Li et al. (+9 more)

Synthetic three-dimensional (3D) light fields provide a new route to imprinting chirality on achiral matter through light–matter interaction. Although previous work has numerically demonstrated that chirality can be imprinted on the photoelectron momentum spectrum of atoms, a transparent analytical physical picture that links the structure of the driving field to the chirality of the spectrum is still an open question. Here, using frequency-domain theory based on nonperturbative quantum electrodynamics (QED), we demonstrate that this chirality originates from coherence between adjacent quantum transition channels. We further find that a symmetry transformation introduces into the coherence term a symmetry-breaking phase shift ($\Phi_{\mathrm{SBPS}}$), which can be tuned by varying the laser-field parameters to preserve or break the corresponding symmetry in the spectrum. Once all such symmetries are broken, the momentum spectrum becomes chiral. In particular, for the noncollinear two-color 3D light field considered here, the spectrum is chiral for even $f=\omega_2/\omega_1$ and achiral for odd $f$. Our results provide a microscopic interpretation of chirality imprinting and establish a framework for predicting and controlling chiral electron wave packets with synthetic 3D light fields.
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All authors Junxin Yuan, Yuhong Li, Fei Li, Jinkai Zhang, Shiyang Zhong, Hao Teng, Yujun Yang, Yingchun Guo, Zhiyi Wei, Jing Chen, Xiaojun Liu, Bingbing Wang

Friday 9 October

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

Experimental observation of Higgs oscillations and their power-law decay across pairing regimes in a cavity QED quantum simulator

Chitose Maruko, Haoqing Zhang, Eliot A. Bohr et al. (+6 more)

Understanding how pairing correlations in superconductors evolve out of equilibrium is a central challenge in quantum many-body physics. In systems with $s$-wave pairing, the character of Cooper pairing evolves continuously from a BCS regime of weakly bound, overlapping pairs to a BEC regime of tightly bound molecules, each with distinct excitation spectra. Here we realize and probe pairing dynamics across these regimes using cold, non-degenerate $^{87}$Rb atoms coupled to an optical cavity with Floquet dressing. Our cavity-QED platform emulates fermionic superfluids through a mapping onto Anderson pseudospins, while optical and microwave control tunes the ratio of interactions to single-particle energies, providing a flexible approach complementary to ultracold Feshbach and ultrafast solid-state platforms. Following a quench, we observe persistent pairing and transient oscillations of the order parameter associated with a collective amplitude (Higgs) mode. We find that the decay of these oscillations sharply distinguishes weak- and strong-pairing regimes: in the weak-pairing regime, oscillations decay with a power-law exponent $|\alpha|=0.65(8)$, whereas in the strong-pairing regime the decay is substantially faster, with $|\alpha|>1$. The oscillation frequency is set by the minimum quasiparticle excitation energy, directly linking nonequilibrium dynamics to the underlying excitation spectrum. Our results establish nonequilibrium dynamics as a direct probe of pairing character and collective excitations in interacting quantum systems.
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All authors Chitose Maruko, Haoqing Zhang, Eliot A. Bohr, Leah Huzjak, Anjun Chu, Victor Gurarie, Chengyi Luo, Ana Maria Rey, James K. Thompson

Atomic Physics

Additional ionization during nuclear $\beta^{\pm}$ decay in atomic systems

Alexei M. Frolov

An original method is developed for numerical calculations of probabilities of the bound-free atomic excitations during the nuclear $\beta^{\pm}$ decays in actual atoms and ions. To achieve this goal we have derived and tested the closed analytical formulas for the final state probabilities of different excitations in the few-electron atomic systems. This study is the first non-approximate and essentially complete investigation of the atomic bound-free excitations during the nuclear $\beta^{\pm}$ decays in atoms.
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Atomic Physics

Optical atomic clocks on all-optical atom chips

Yuri B. Ovchinnikov

The feasibility and potential performance of optical clocks based on all-optical atom chips using neutral strontium atoms have been investigated. The key benefits of all-optical atom chips are their ability to trap alkali-earth atoms, and how easily these atoms can be manipulated and examined. The planar configuration of the chip enables ring photonic resonators to be incorporated into its structure, making it a promising candidate for active optical atomic clocks. Using the 'magic wavelengths' of the trapping optical fields (813 nm and 390 nm for strontium atoms) minimises frequency shifts in the intercombination clock transition caused by variations in optical field intensity. However, this frequency shift can be compensated for using optical AC Stark shifts, which are generated by the trapping optical fields and have frequencies below the 'magic frequencies'. Furthermore, it has been demonstrated that atom chip clocks can operate using solely repulsive, blue-detuned evanescent light fields when the attraction of the trapped atoms towards the photonic waveguide is realised through van der Waals forces alone. According to estimates, this could result in the short-term fractional frequency stability of the strontium atom-chip optical clocks being limited to ~10^{-16} per second, with an accuracy of about 5 x 10^{-15} for fractional intensity stability in the trapping light fields of 0.001.
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Atomic Physics · Cross-listed from physics.chem-ph

Quantum dynamics of an ion in an RF quadrupole trap with weak octupolar anharmonicity

Sukanya Jana, Anushree Dey, Pintu Manadal et al. (+1 more)

We investigate the quantum dynamics of a single ion confined in a radio-frequency (RF) Paul trap in the presence of weak octupole-induced anharmonicity, as can occur in realistic ion-trap potential. The explicitly time-dependent quadrupole potential is treated in a reference-oscillator Fock basis, allowing the effects of the RF drive and the quartic correction to be resolved directly at the level of motional-state couplings. While the quadratic RF interaction generates $\Delta n=\pm2$ transitions and Gaussian squeezing, the quartic contribution opens additional $\Delta n=\pm4$ coupling pathways. Starting from the reference-oscillator vacuum, we show that the octupole interaction broadens the even-parity Fock-state distribution and enhances the phonon-number fluctuations more strongly than the mean occupation. At the same time, the RF-induced sub-vacuum quadrature squeezing remains robust, although its magnitude and orientation are modified by the quartic interaction. The number statistics and quadrature fluctuations therefore respond differently to the same nonlinear perturbation, reflecting the distinct roles of Fock-space redistribution and phase coherence. The resulting dynamics provide a quantum-mechanical characterization of weak octupole corrections beyond the ideal quadrupole approximation and clarify how realistic anharmonicities modify nonclassical trapped-ion motion. Importantly, the motional nonclassicality remains robust against the weak octupole perturbation, as evidenced by persistent sub-vacuum quadrature squeezing and Klyshko-inequality violation. These results characterize how realistic anharmonic corrections reshape trapped-ion motion beyond the ideal quadrupole approximation.
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All authors Sukanya Jana, Anushree Dey, Pintu Manadal, Nabanita Deb

Atomic Physics · Cross-listed from cs.LG

Recovering Irreducible Three-Body Interactions with Lagrangian Neural Networks

Sena Kalabalik, Sukru Caglar, Abdullah Umut Hamzaogullari et al. (+1 more)

Lagrangian Neural Networks (LNNs) learn mechanical systems from trajectory data by parameterizing a scalar Lagrangian and deriving the dynamics through the Euler-Lagrange equations, biasing the model toward motion that respects the variational structure of mechanics. The interactions studied so far have been pairwise-additive, leaving open whether LNNs can recover an irreducible many-body interaction from motion alone. We address this using the Axilrod-Teller triple-dipole interaction, the leading three-body dispersion term, whose dependence on the collective geometry of three particles cannot be represented by any sum of pairwise terms. We prescribe the kinetic energy exactly and learn only the potential, as a function of interparticle distances and angles. Combined with a signal-aware sampling strategy that concentrates training data where the three-body signal is strongest while preserving broad coverage of configuration space, this recovers the interaction from accelerations alone. The learned potential reproduces the radial scaling, angular dependence, and characteristic sign reversal of the Axilrod-Teller interaction, and generates stable trajectories. Embedding it within a pairwise Lennard-Jones potential lets us examine its observability: the three-body term is recovered once its dynamical signature exceeds the residual modeling error, which it does cleanly at amplified coupling but not at the coupling of a real noble gas, bracketing the transition between the two. Finally, symbolic regression on the trained potential, with no assumed functional form, returns the Axilrod-Teller expression with angular numerator, radial law, and coupling constant intact. An LNN with domain-specific structure can thus recover an irreducible three-body interaction from trajectories as a closed-form law, pointing toward learning interaction laws whose structure is not known a priori.
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All authors Sena Kalabalik, Sukru Caglar, Abdullah Umut Hamzaogullari, Arkadas Ozakin

Thursday 8 October

Atomic Physics · Cross-listed from quant-ph

Correlated Pair Creation with Positive- and Negative-Frequency Oscillators in a Trapped-Ion Quantum Simulator

Visal So, Mingjian Zhu, Han Pu et al. (+1 more)

Spin-dependent forces enable independent control over the effective frequencies of bosonic motional modes and their coupling strengths to spins in trapped-ion spin-boson quantum simulators. We show that the relative signs of these effective frequencies provide an important programmable resource for engineering distinct multimode dynamics. Focusing on a two-mode quantum Rabi model, changing the frequencies of the two modes from the same sign to opposite signs reorganizes the resonance structure of the spin-mediated bosonic interaction, converting the dominant resonant process from excitation exchange to correlated pair creation. In the dispersive regime, the resulting effective interaction realizes a two-mode parametric amplifier with stable oscillatory, critical, and exponentially amplifying regimes separated by a spin-dependent instability threshold. Across these regimes, the dynamics generate collective-quadrature squeezing and bipartite motional entanglement. Preparing the spin in a coherent superposition further allows different spin components to experience distinct stability regimes, generating tripartite spin-boson entanglement, while spin postselection can coherently combine the conditional bosonic branches to generate non-Gaussian entangled bosonic states. Finally, we outline an implementation using parameters within reach of current trapped-ion platforms.
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All authors Visal So, Mingjian Zhu, Han Pu, Guido Pagano

Atomic Physics

Local polarization control of optical tweezer arrays

Xiangkai Sun, Richard Bing-Shiun Tsai, Andrew Winnicki et al. (+4 more)

Optical tweezer arrays trapping ultracold atoms and molecules are a versatile quantum science platform with broad impact in quantum simulation, quantum computation, and quantum metrology. The polarization dependence of anisotropic vector and tensor light shifts offers a degree of freedom for precise quantum state engineering of trapped particles. Similarly, state-selective operations depend on the polarization of the addressing light through the atom–light coupling strength. Yet, methods for controlling the polarization of individual tweezers or local addressing beams remain an experimental challenge. Here, we demonstrate independent, site-resolved linear polarization rotation across an optical tweezer array by exploiting the local birefringence tunability of a spatial light modulator. Applying this capability to an array of $^{88}\rm{Sr}$ atoms, we homogenize differential light shifts imparted by the 813-nm tweezers to the narrow ${^1{\rm S}_0}\leftrightarrow{^3{\rm P}_1}$ transition, enabling sideband cooling under a magic-angle condition. Furthermore, we show dynamic transport of trapped atoms across distinct polarization zones with high survival and preserved coherence. Finally, we characterize tweezer polarization noise and demonstrate closed-loop stabilization referenced to the atomic transition frequency, reaching mrad-level stability. Our work establishes a technique for manipulating polarization-sensitive atomic and molecular transitions in tweezer architectures, with immediate applications to optical tweezer clocks and multi-zone quantum processors.
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All authors Xiangkai Sun, Richard Bing-Shiun Tsai, Andrew Winnicki, Yuan Le, Kon H. Leung, Nelson Darkwah Oppong, Manuel Endres

Atomic Physics

Response of the near-threshold resonances of the $\bm{dt\mu}$ molecular ion to an effective atomic $2s$–$2p$ splitting

Yi Zhang

For the nonrelativistic three-body Coulomb Hamiltonian, near-threshold resonances of the deuterium–tritium muonic molecular ion ($dt\mu$) are supported by the long-range dipole coupling between degenerate atomic $2s$ and $2p$ states. We study the effect of atomic $2s$–$2p$ splitting on their positions and decay widths. Three-body complex-absorbing-potential calculations resolve additional members of the $L^\pi=0^+$ and $1^-$ series. Their geometric spacing agrees with that expected from the $1/R^2$ dipole attraction, where $R$ is the atom–nucleus separation. To assess the effect of splitting, we scan a prescribed $2s$–$2p$ interval using an effective potential in a spin-independent, nonrelativistic Hamiltonian. This models the atomic splitting without an explicit Lamb-shift calculation. Within this model, the studied resonances lie closer to the $d\mu(2s)+t$ threshold and have smaller Coulomb decay widths than in the degenerate case. At an effective interval of $0.2\eV$, the seventh $1^-$ member lies within $2\meV$ of this threshold with a full width of about $4\meV$, compared with $48$ and $15.6\meV$ at degeneracy. These values characterize the response within the tested numerical representations. Its width decreases, but its separation from the threshold decreases more strongly. The long-range analysis attributes these shifts and width reductions to modified dipole mixing. It further suggests that atomic $2s$–$2p$ splitting may truncate the infinite accumulation of resonances predicted for degenerate atomic $2s$ and $2p$ levels.
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Atomic Physics · Cross-listed from physics.optics

Optical Signals Synthesized from an Optical Lattice Clock with Uncertainty of 1.3E-17

Yuan Yao, Jinpeng Zou, Haosen Shi et al. (+3 more)

We report an accurate optical frequency synthesizer, which can generate single-frequency laser light with high frequency stability and accuracy at desired frequencies over a wide optical region. The frequency of the output signal is divided from an 171Yb optical lattice clock via an accurate optical frequency divider based on an optical frequency comb. Therefore, the output of the optical frequency synthesizer inherits the frequency accuracy from the Yb optical clock. The frequency uncertainty of the 171Yb optical lattice clock is evaluated to be 6.8 mHz, corresponding to a fractional frequency uncertainty of 1.3E-17, mainly limited by the blackbody radiation shift and the lattice-induced light shift.
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All authors Yuan Yao, Jinpeng Zou, Haosen Shi, Hongfu Yu, Longsheng Ma, Yanyi Jiang

Wednesday 7 October

Atomic Physics · Cross-listed from quant-ph

Fast entanglement generation via cavity-mediated nematic tensor dynamics

Stuart J. Masson

Many-body entanglement in atomic ensembles offers the potential for enhanced sensing devices. Entanglement can be generated by interfacing atoms with a cavity. Traditional methods use effective two-level systems isolated from more complex atomic level structures. However, alternative strategies allow entanglement to be generated in atoms confined to a single hyperfine manifold. These strategies enable entanglement in ways fundamentally not available to two-level systems but feature extremely slow dynamics due to requiring strongly off-resonant laser fields. Here, I show that equivalent squeezing dynamics can be achieved much closer to resonance, offering entanglement generation over a hundred times faster than typical experiments. Furthermore, the Hamiltonian can be used to speed up the creation of maximally entangled states via adiabatic passage.
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Atomic Physics

Disorder-induced nuclear-transition doublet at nominally cubic $^{229}$Th sites

Andrei Derevianko

The $^{229}$Th nuclear clock transition is inhomogeneously broadened even at sites of nominally cubic symmetry, where the electric-field gradient of the ideal lattice vanishes. We show that dilute static point-defect disorder produces a doublet with a zero at the quadrupole-free frequency. The doublet is symmetric in the isotropic approximation; size misfit point defects introduce a small lobe asymmetry without removing the zero. Charged and size-misfit defects share inverse-cube scaling and an approximately common normalized profile, whose width separates into a host-controlled background and a term linear in the $^{229}$Th density. In a heavily doped $^{229}$Th:CaF$_2$ crystal [Nature 657, 626 (2026)], the thorium-linked contribution is comparable to the measured 1.1 MHz width; in a lightly doped crystal [arXiv:2606.08870], the 0.9 MHz width bounds the host background. Neither spectrum shows the predicted dip, which points to the presence of extended defects in both crystals. If the predicted dip is resolved, it can provide a nuclear-clock discriminator referenced to the quadrupole-free nuclear transition frequency.
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