24,322 papers in this slice of arXiv.
Jun-Rong Chen, Guo-Qing Qin, Peng-Fu Liang +7
High-precision phase measurement of microwave fields underpins a wide range of applications, including wireless communications, distributed radar, plasma diagnostics, and antenna metrology. Existing Rydberg-atom-based approaches, however, often face trade-offs among phase resolution, measurement range, and system complexity. Here we demonstrate a Rydberg-atom-based microwave Mach-Zehnder-type interferometer using a dual-local-oscillator configuration. The two local oscillators establish two coherent interferometric pathways in the Rydberg medium. Their coherent mixing with the signal field produces an interferometric intermediate-frequency output governed by a phase-to-intensity transfer characteristic that enables critical-point enhancement. This scheme supports direct phase retrieval with a resolution exceeding 0.1∘ and unambiguous full
Junwoo Jung, Jaewook Ahn
Whether neutral-atom quantum optimization protocols exhibit genuine concentration toward low-energy solution structure remains an open question. Here, we introduce a shots-to-approximate-solution metric, STS(r), where r denotes the approximation ratio, and evaluate it using postprocessed outputs modeled by a degeneracy-weighted shell distribution governed by a single effective parameter, β, that quantifies concentration toward near-optimal independent sets. To extract the genuine concentration effect in the quantum data, we apply identical postprocessing to both experimental bitstrings and randomly generated bitstrings with matched excitation density, thereby constructing an excitation-matched random baseline. Experiments on programmable Rydberg-atom arrays with system sizes up to 125 sites show that quantum annealing consistently exceeds the random baseline, demonstrating enhanced concentration toward low-energy solution structure beyond what can be attributed solely to excitation density. The results further reveal two distinct target-dependent regimes. For near-exact targets with r≈1, the required shot count grows exponentially with system size and is reduced at the same exponential level by quantum annealing within the shell-model description. By contrast, for relaxed targets, the shot cost becomes effectively constant, and the corresponding quantum enhancement diminishes, with the classical postprocessing heuristic alone reaching the target in order-unity attempts. Together, these results establish an operational method for quantifying quantum optimization performance and clarify the regimes under which quantum approaches can yield practical benefits.
J. Pérez-Ríos, D. B. Cassidy
Precise measurements of the metastable helium (1s)(2s)3S1 ionization energy have revealed a 9σ discrepancy with QED theory that persists in isotopic measurements, suggesting a leptophilic bosonic interaction as a possible explanation. A subsequent investigation of such interactions has concluded that only a scalar boson interaction is consistent with the He observations. Taking this as a starting point, we derive the response of positronium energy levels to the corresponding finite-range Yukawa potential, using exact hydrogenic matrix elements and a numerical helium calculation. Across the viable mediator-mass range of 0-800 eV, the He anomaly interpreted in this way implies a positronium 13S1→23S1 shift ranging from 0.250-0.850 MHz, and a 2S-ionization shift of 0.14-0.21 MHz. We discuss the feasibility of observing these shifts experimentally.
Neethu Abraham, P. Giannakeas, Matthew T. Eiles
We investigate predissociation in homonuclear (87Rb∗87Rb+) and heteronuclear (87Rb∗7Li+) long-range Rydberg atom-ion molecules. Owing to their micron-scale bond lengths, these dissociate on time scales far removed from those of more tightly bound diatomic molecules. We employ the eigenchannel R-matrix method to compute predissociation rates for a broad range of principal quantum numbers n. The rates depend strongly on the mass, but more remarkably display a rapid and periodic variation as a function of n as well as within a single vibrational ladder. A semiclassical Landau-Zener-Stückelberg analysis reveals that Stückelberg interference governs the decay process and produces the observed variation in the molecular lifetime. Although the heavy mass of the homonuclear Rb molecule constrains its predissociation rates to a sub-kHz level, the lighter molecule 87Rb∗7Li+ dissociates on time scales competitive with radiative and collisional decay. This can enable in situ study of non-adiabatic decay via ion microscopy.
Sasan Rezaee, Fatemeh Mohammad Dezashibi, Ould el Moctar +1
Morphology transfer of 2D Janus MXenes into nanoscrolls unlocks unusual properties. Although a scalable synthesis route has been experimentally verified, the atomistic mechanism underlying nanoscroll formation remains poorly understood. We use large-scale reactive molecular dynamics simulations, validated against density functional theory (DFT) and experimental structural and elastic properties, to investigate stability and quantify the driving forces and geometry governing nanoscroll formation in three Janus MXenes, (Tx)Ti2C(Ty), where (Tx) and (Ty) denote the bottom and top surface terminations among bare (-b), -O, and -OH. Both square and infinitely wide flakes with lengths ranging from 10 to over 120 nm are simulated. We find that 1-7% lattice-induced strain generates a bending moment in these structures. The sheet scrolls, curves, or forms a nanotube depending on the resulting curvature and initial sheet size. For MXenes with an initial length of 120 nm, multiwalled nanoscrolls form with interlayer distances of around 0.7 nm and inner diameters of about 7 nm for (O)Ti2C(OH) and (b)Ti2C(OH), whereas (b)Ti2C(O) instead produces a much larger interlayer distance of around 1.7 nm and an inner diameter exceeding 20 nm. We show that spontaneous scrolling of a Janus MXene in the presence of an anchored nanoparticle produces a core@shell composite, in which the particle locally deforms the nanoscroll and widens the interlayer channels. This locally tunable, enlarged interlayer spacing offers a promising design route for MXene-based energy-storage electrodes. However, our simulations reveal H2 gas release during encapsulation, which promotes nanobubble formation that can reduce battery life.
Przemyslaw Jozwik, Cyprian Mieszczynski, Renata Ratajczak +1
Ion channeling and backscattering techniques are powerful tools for studying crystal lattice disorders and defect structures in crystalline materials. However, the accurate interpretation of channeling phenomena necessitates the utilization of simulation models that account for the intricate interactions between point defects, dislocations, and extended defect clusters. The present paper introduces a Monte Carlo method that reproduces experimental spectra over a wide range of analyzing beam energies and enables quantitative identification of defect types and distributions. The simulations reveal characteristic energy dependencies that distinguish point defects from extended defects, offering a novel perspective on disturbances caused, for example, by ion implantation in metals and semiconductors. To this end, the McChasy code has been developed as a flexible and accessible tool for scientists, enabling the modeling of various crystal systems, including complex semiconductors, multilayer epitaxial films, and oxide crystals. The program's integration of experimental data on ion channeling with defect modeling establishes a robust framework for defect analysis in materials science. The present article expounds upon the simulation capabilities of the program by reproducing the characteristic "elbows" in channeling spectra that were previously observed in experiments conducted on Cu crystals.
S. Liu, M. Watts, C. Diver +13
A system of actively-shielded coils and mu-metal shields is devised, constructed and shown to provide the stable and spatially uniform magnetic field needed for the ACME III electron electric dipole moment (eEDM) measurement. Two layers of current-carrying coils, enclosed within three layers of ferromagnetic shields, produce a field that varies by less than 1 nT (10 ) within the 1 m × 4.2 cm × 4.2 cm interior volume in which a beam of ThO molecules are probed as they precess. The demountable shields are constructed from rectangular mu-metal plates. The largest, with a mass of 19 kg and an area of 2.18 m × 0.75 m, is easily carried by two people and just fits within a large available annealing oven. The assembly design facilitates low-stress mounting and handling to suppress changes in the magnetic properties of the mu metal, and also provides modular access to apparatus within the coils for maintenance and upgrades. The nearly static external ambient field is reduced within the shielded precession volume by up to a factor of 105. During the magnetic field reversals that ACME uses to suppress systematic uncertainties, the ``actively-shielded'' coil largely cancels out its external fringing field to minimize the magnetization of the mu metal. Even though the shields are only 10 cm outside the coils, shield degaussing after every magnetic field reversal is not required. The non-reversing residual field stays below 1 nT for up to 17 hours when the field is reversed every 30 seconds, for example. The measured performance, compared to the previous generation ACME II apparatus, suggests that the magnetic-field-related systematic uncertainties for ACME III will be smaller by an estimated factor of 40 despite a five times longer precession volume and the use of three magnetic shielding layers rather than five.
Tim E. Lellinger, Liss V. Rodriguez, Patrick Muller +29
Atomic nuclei are strongly correlated quantum many-body systems, and how their shell structure evolves with increasing neutron excess remains a central open question in nuclear physics. Calcium isotopes are an ideal testing ground: alongside the traditional magic numbers N=20,28, new shell closures have been proposed at N=32,34 (52,54Ca). While the charge radius rises rapidly towards N=32, further moments and radii in the isotopic chain have remained inaccessible due to the low production yield of a few ions per second. Here we apply a highly sensitive collinear laser spectroscopy technique, which reveals a strikingly simple behaviour: adding one neutron to 52Ca yields a pure single-particle magnetic dipole moment in 53Ca, while the charge-radius slope towards 54Ca exceeds that towards 52Ca. This provides strong evidence for a robust N=32 shell closure and stringently constrains nuclear structure models.
Massimiliano Bazzi, Francesco Clozza, Carlo Guaraldo +38
The study of the strong interaction among hadrons at low energies remains one of the key challenges in fundamental physics because of its non-perturbative nature, which makes theoretical descriptions strongly dependent on experimental input. Although substantial progress has been made for systems involving up and down quarks, theoretical models in the strangeness sector continue to face limitations due to the lack of experimental data. Kaonic atoms provide a powerful tool to study the low-energy strong interaction with strangeness through the energy shifts and widths induced on their lowest atomic levels. In this context, kaonic deuterium X-ray spectroscopy has long represented one of the major open challenges in hadronic-atom physics because of its extremely low X-ray yield. This measurement is particularly important because it gives access to the experimentally inaccessible K−n interaction at threshold energy. Here, we report the first observation of kaonic deuterium X-ray transitions, performed with the SIDDHARTA-2 experiment at the DAΦNE collider. We determine the strong-interaction shift and width of the 1s level to be ε1s=−810.9±24.5(stat)±2.1(syst)eV and Γ1s=812±97(stat)±33(syst)eV, respectively. This measurement constitutes the most precise experimental determination of the K−d strong interaction at threshold and allows discrimination among competing theoretical models. Combined with the kaonic hydrogen measurement, this result provides the experimental input required to determine the isospin-dependent K−N scattering lengths, with implications for the description of the nature of the first predicted hadronic molecular state, the Λ(1405), and neutron-rich matter.
H Olivares-Pilon, JC Lopez-Vieyra, AV Turbiner
Two alternative approaches for studying Helium-like atomic ions in non-relativistic quantum mechanics are proposed: (I) a numerical approach, based on the Lagrange-mesh method which can easily reach up to 14-15 significant digits in the energy spectrum for any nuclear charge Z with modest CPU time in single processor mode and (II) a highly-accurate, few-parametric interpolation formula for the energies vs. Z. The interpolation formula of general nature is proposed, it can be applied to the energies of any excited state of the helium-like sequence. It is based on matching the 1/Z-expansion at large Z and the Puiseux expansion with integer and half-integer powers around the so-called second critical charge ZB, introduced by F and D Stillinger (1969, 1974), confirmed by the present authors in 2019 for the ground state 11S, then revisited here, and extended to the excited states in the present work. For example for the first two spin-singlet 11S, 21S and the first two spin-triplet 23S, 33S states this interpolation formula with nine free parameters can reach an accuracy of 10-14 significant digits (s.d.) in the energies for any physically-relevant nuclear charge Z, giving absolute accuracy at large Z. Many results are obtained for the first time.
Lin Su, Michal Szurek, Alec Douglas +2
Quantum coherence underlies collective quantum phenomena and emerging quantum technologies. Quantum gas microscopes have transformed quantum simulation by providing projective snapshots of many-body states with single-atom resolution, but spatially resolved measurements of off-diagonal correlations have remained elusive. Here, using the Talbot effect, we introduce a quantum coherence microscope that maps off-diagonal correlations onto site-resolved density signals with near-single-site resolution. We use this technique to locally probe the superfluid-Mott transition in a layer of a three-dimensional optical lattice and to measure coherence beyond nearest neighbors in an engineered potential landscape. By mapping off-diagonal correlations onto density signals through controlled Talbot evolution, this work opens new possibilities for accessing observables beyond the density basis through tailored matter-wave evolution and recapture.
K. Foster, S. Majumdar, D. Fischer
Photoionization induced by trapping and auxiliary laser fields is an inherent feature of many laser-cooling and optical trapping experiments, yet its microscopic dynamics are rarely investigated directly. In this work, we employ a reaction microscope implementing an event-by-event photoionization time retrieval technique to extend momentum-resolved photoelectron spectroscopy to continuous-wave laser--atom interactions. We investigate low-intensity multicolor photoionization of laser-cooled lithium atoms confined in an all-optical trap. Complete three-dimensional electron momentum distributions and kinetic-energy spectra recorded for different laser wavelengths and polarization configurations identify resonant excitation of the 5p and 5f states and reveal an additional ionization channel following spontaneous decay from the 5f to the 4d state. A pronounced polarization dependence of the photoionization yield is explained by magnetic-sublevel selection rules and the coherent interference of different virtual excitation pathways. These results demonstrate that reaction microscopy combined with event-by-event time reconstruction provides a powerful approach for investigating microscopic electronic dynamics in laser-cooled atomic systems and offers new insight into photoionization processes occurring during optical trapping.
Joel Gomes Baptista, Louis Pagot, Sébastien Merlet +2
Quasi-Bragg regime is a good compromise for large-momentum-transfer atom interferometry, allowing for scaling up the interferometric area, while constraining the population of unwanted states. Separation of momentum states via standard time of flight methods, however, can be challenging when using laser-cooled atoms, rather than ultracold atoms with sub-recoil velocity distribution. To overcome this limit, we use Raman spectroscopy for stroboscopic sampling of the atomic state evolution in momentum space during the interrogating laser pulses. We quantitatively characterize atom optics employing two-photon (2___k) and multi-photon (6___k) Bragg transitions, the latter being optionally enhanced with optimal control protocol. We closely match the observed dynamics of the atomic state with simulations. Finally, we perform momentum spectroscopy of the output states in a 6___k Bragg gravimeter.
David Rodríguez Fernández, Manuel Alejandro Lefrán Torres, Jaime Javier Borges Márquez +6
High-resolution laser spectroscopy of the 85Rb2, 85Rb87Rb
Rohit Tyagi, L. C. Tribedi, M. K. Harbola +1
We report energy and angle resolved absolute cross section measurements for LMM Auger-Meitner electron emission following collisions of hundred keV protons and Ar3+/6+ ion with an atomic Ar target. The double differential cross section spectra show distinct contributions from target and projectile Auger-Meitner decay. The projectile emission exhibits the expected Doppler shift for various angles of electron emission, and the measured peak energies are in excellent agreement with kinematic calculations. The energy integrated cross sections show isotropic angular distribution for target and projectile species in their respective rest frames. The Auger-Meitner peak energy for target as well as projectile emission show significant difference in comparison to the characteristic L-MM Auger-Meitner energy peak from atomic Ar. The experimental measurements have been complimented with development of a theoretical model to calculate the transition probabilities corresponding to prominent L-MM Auger-Meitner transitions in neutral and multiply charged Ar atom. Comparison between measured and calculated spectra shows that the measured emission peak at approximately 150 eV originates from Auger-Meitner decay of Ar4+ ions. The peak energies for target and projectile emission are found to be equal, independent of the initial projectile charge state. This indicates that the decay occurs following extensive multiple ionization, charge exchange processes resulting in charge-state equilibration of the collision partners. The results demonstrate that collision-induced electronic rearrangement strongly modifies the Auger-Meitner spectra and provide evidence for an equilibrium target-projectile charge state in low-energy Arq+−Ar collisions.
C. Brandau, P. Micke, I. Hartl +6
The prospects and the implementation of single-ion nuclear clocks of 229Thq+ ions in their highest charge states q=90,…,87 are discussed. Highly-ionized-thorium clocks are ideal for tests of fundamental interactions since the ions are elementary quantum systems composed of only a few building blocks. Two cases of 229Thq+ clocks excel: a) one-electron 229Th89+ that combines two nuclear-clock transitions in the VUV with hyperfine IR atomic-clock transitions, and, b) fully ionized 229Th90+ which constitutes the prototype of a nuclear clock, one without any electrons. We evaluate the feasibility of such clocks by means of quantum logic spectroscopy (QLS) in linear Paul traps. Due to its universal nature, the QLS approach allows for systematic clock comparisons using different charge states as well as different spectroscopy transitions on the same experimental platform. A valuable asset towards single-ion 229Thq+ clocks is the process of nuclear hyperfine mixing that enables the tunability of the natural linewidth of the clock transition over more than five orders of magnitude by changing the charge state.
Dong-Yu Huang, Jian Wang, Xiao-Long Zhou +8
Quantum nonlocality, typically revealed through entanglement distribution across quantum networks, is a cornerstone of quantum information science. Long-distance distribution of entanglement requires the information carrier, i.e. flying photons, to operate in the minimum-loss telecom band of optical fiber. While extensive efforts have been devoted to the direct generation of entanglement between C-band telecom photons and various stationary spins, the verification of quantum nonlocality remains an outstanding challenge. Here, utilizing a dipole transition in rubidium atoms with a wavelength of 1530 nm and a cavity-assisted protocol, we achieve resonant excitation and direct emission of C-band telecom photons from a single atom, generating spin-photon entanglement with a measured Bell state fidelity exceeding 91.4%. We then verify Bell nonlocality by observing a Bell inequality violation of 2.455(77) > 2 using this high-quality entangled pair. These results extend the wavelength of a single-atom quantum emitter to the telecom C-band, achieving sufficiently high-fidelity spin-photon entanglement to finally verify Bell nonlocality. This work thereby provides a promising building block for a large-scale atom-based quantum network capable of distributed quantum metrology and long-distance quantum communication.
O. Farion, M. Pourzand, J. M. McGuirk
Domain walls are carriers of spin transport whose controlled manipulation underlies a wide range of spintronic and information-processing technologies. Here we demonstrate tunable domain-wall transport in a weakly interacting nondegenerate ultracold Bose gas. We initialize a three-domain pseudo-spin-1/2 texture and observe spontaneous propagation of long-lived domain walls driven by exchange-mediated spin currents. By varying the orientation of the spin domains, we control the balance of spin currents across the walls and thereby tune their trajectories, including reversals of the initial direction of motion. Measurements reveal a crossover from an exchange-stabilized regime, in which coherent spin-exchange collisions suppress wall motion, to a diffusion-dominated regime characterized by rapid transport at thermal velocities. Numerical solutions of a quantum Boltzmann equation reproduce the observed dynamics and identify transverse phase gradients as an important control parameter governing domain-wall propagation. These results establish coherence and phase engineering as tools for programming spin transport in ultracold gases and provide a route toward controllable domain-wall dynamics in atomtronic systems.
Yuxi Yang, Arian Jadbabaie, Lukáš Félix Pašteka +3
Searches for P,T-violating electromagnetic moments are among the most sensitive probes of physics beyond the Standard Model. Extending beyond current limits will benefit from molecules with fully controllable orientation at low electric fields, long coherence times, and laser coolability---all offered by asymmetric top molecules (ATMs). Exploiting the intrinsic rotational K-doubling in ATMs and the associated long-lived (T1≳10 s) parity doublets afforded by C2v symmetry and nuclear-spin statistics, these species combine large electric polarizability with long coherence times in modest laboratory fields. We study alkaline-earth(-like) monoamides, M--NH2 (M = Ca, Sr, Ba, Yb, Ra), which possess favorable electronic structure for laser cooling. We perform ab initio calculations of fine and hyperfine constants, identifying the importance of relativistic effects in the spin-rotation tensor. An effective Hamiltonian then models the rotational and hyperfine structure of the vibronic ground state, quantifying electron electric dipole moment (EDM) sensitivities and identifying feasible measurement schemes. We compute the effect of external fields and identify engineered clock transitions that suppress sensitivity to external perturbations while retaining strong EDM sensitivity, and characterize the magic trapping conditions that null differential light shifts in an optical trap. Under these conditions we project a statistical electron-EDM sensitivity over an order of magnitude beyond current best experimental limits, with further gains available from increased molecule number and coherence time. Our results establish asymmetric top molecules as a tunable platform for sensitive symmetry-violation measurements with long coherence times.
Joerg Jaeckel, Lucas Puetter
We investigate how scalar-mediated potentials with Lorentz-violating couplings to Standard Model fermions affect spectroscopic observables in atoms and highly charged ions. Suitable combinations of an ordinary scalar and a time-like component of a Lorentz violating vector coupling allow for a split into "matter" and "antimatter" couplings, at least in the non-relativistic limit. By considering hydrogen and antihydrogen spectra, we access both matter and antimatter couplings. While relativistic effects alone lift degeneracies in ordinary hydrogen, providing indirect access to antimatter couplings, comparisons with antihydrogen measurements lead to significantly improved sensitivity to the antimatter couplings. In highly charged ions, enhanced relativistic effects further amplify the sensitivity, compensating for reduced experimental precision and larger theoretical uncertainties. We obtain the strongest bounds to date for scalar masses mφ≳400keV. For comparison, we estimate astrophysical constraints on the same parameter space, providing strong bounds even on antimatter couplings, despite stars being predominantly composed of matter.