The effective electron neutrino mass can be determined by analyzing the end-point region of the ^{163}Ho electron capture spectrum, provided a measurement with high-energy resolution and high statistics using calorimetric techniques. Here, the Electron Capture in ^{163}Ho Collaboration (ECHo) presents an analysis of the most precise ^{163}Ho spectrum currently available, obtained with the ECHo-1k experiment and comprising about 200 million events. A very low background rate of b_{const}=9.1(1.3)×10^{-6} eV/pixel/day was achieved allowing for a reliable analysis of the end-point region. The derived end-point energy Q=2862(4)  eV is in excellent agreement with the one independently determined via Penning-trap mass spectrometry of Q=2863.2(6)  eV [Ch. Schweiger et al., Nat. Phys. 226, 921 (2024)NPAHAX1745-247310.1038/s41567-024-02461-9]. The upper limit of the effective electron neutrino mass is improved by almost a factor of 2 compared to the lowest current value [B. K. Alpert et al., Phys. Rev. Lett. 135, 141801 (2025)PRLTAO0031-900710.1103/s9vl-7n24], reaching m_{ν_{e}}<15  eV/c^{2} (90% credible interval).

Global navigation satellite systems (GNSS) are often disrupted or unavailable at sea, and unaided inertial navigation systems (INS) drift without correction. Quantum-sensing-based gravity map matching offers a passive, infrastructure-free aid, but field demonstrations of GNSS-free quantum gravimetric navigation have not been reported. Here we perform gravity map matching and fine-resolution gravity survey with a mobile quantum gravimeter aboard a 29 m surface vessel. We hybridize an atomic sensor with a classical accelerometer for bias stabilization and independently mechanize a navigation-grade IMU, all installed in an uncontrolled cabin with no environmental stabilization or calibration. Operated in both gimbaled and strapdown configurations over identical traversals, the hybrid sensor corrected the inertial solution over an 83 km maritime trajectory by referencing locally measured gravity to a satellite-derived anomaly map. Gravity-aiding constrains INS drift and delivers bounded positioning at nautical-mile-level accuracy, with GNSS excluded throughout the measurement chain. In a separate GNSS-referenced mode, the same system surveyed coastal routes up to Sea State 4, achieving mGal-level agreement with gravimetric maps and sub-mGal repeatability and stability, with gimbaled and strapdown operation performing comparably. Resolved anomalies reach an along-track scale of 300 m, 50X finer than the satellite map's half-power wavelength. A 56 h stationary test shows atom referencing lowers long-term drift 70X versus the classical channel alone. These results provide the first same-instrument comparison of gimbaled and strapdown mobile quantum gravimetry and the first fully GNSS-independent gravity-map-matching navigation demonstration using a quantum gravimeter, pointing toward compact, autonomous-platform-ready quantum sensing for GNSS-denied maritime navigation and survey.

In this Letter, we present mass-ratio measurements on highly charged Yb$^{42+}$ ions with a precision of $4\times 10^{-12}$ and isotope-shift measurements on Yb$^{+}$ on the $^{2}$S$_{1/2}$ $\to$ $^{2}$D$_{5/2}$ and $^{2}$S$_{1/2}$ $\to$ $^{2}$F$_{7/2}$ transitions with a precision of $4\times 10^{-9}$ for the isotopes $^{168,170,172,174,176}$Yb. We present a new method that allows us to extract higher-order changes in the nuclear charge distribution along the Yb isotope chain, benchmarking ab-initio nuclear structure calculations. Additionally, we perform a King plot analysis to set bounds on a fifth force in the keV$/c^2$ to MeV$/c^2$ range coupling to electrons and neutrons.

Experimental implementations of quantum simulation must balance control‐field‐induced decoherence with the controllability of the quantum system. The ratio of coherent interaction strength to decoherence induced by stimulated emission in atomic systems is typically determined by hardware constraints, limiting the flexibility needed to explore different operating regimes. Here, an optomechanical system is presented for in situ tuning of the coherent spin‐motion and spin‐spin interaction strength in 2D ion crystals in a Penning trap. Enabled by precision closed‐loop piezo‐actuated positioners integrated into the confined space of a superconducting magnet's bore, the system allows tuning of the angle‐of‐incidence of Raman laser beams up to , governing the ratio of coherent to incoherent light‐matter interaction for fixed optical power. System characterization involves measurements of the induced mean‐field spin precession under the application of an optical dipole force in ion crystals cooled below the Doppler limit through electromagnetically induced transparency cooling. These experiments show approximately a variation in the coherent to incoherent interaction ratio with changing , consistent with theoretical predictions. The system stability is characterized over 6000 s, resulting in a drift rate of h–1. These technical developments will be crucial in future quantum simulations and sensing applications.

The investigation of the absolute scale of the effective neutrino mass remains challenging due to the exclusively weak interaction of neutrinos with all known particles in the standard model of particle physics. At present, the most precise and least-model-dependent upper limit on the electron antineutrino mass is set by the Karlsruhe Tritium Neutrino Experiment (KATRIN) from the analysis of the tritium beta-decay. Another promising approach is the electron capture in Ho-163, which is under investigation using microcalorimetry by the Electron Capture in Holmium (ECHo) and HOLMES collaborations. An independently measured Q value for this process is vital for the assessment of systematic uncertainties in the neutrino mass determination. Here we report a direct, independent determination of this Q value by measuring the free-space cyclotron frequency ratio of highly charged ions of Ho-163 and Dy-163 in the Penning-trap experiment PENTATRAP. Combining this ratio with atomic physics calculations of the electronic binding energies yields a Q value of 2,863.2 +/- 0.6 eV c(-2), which represents a more than 50-fold improvement over the state of the art. This will enable the determination of the electron neutrino mass on a sub-electronvolt level from the analysis of the electron capture in Ho-163.

Resolving the locations and discriminating the spin states of individual trapped ions with high fidelity is critical for a large class of applications in quantum computing, simulation, and sensing. We report on a method for high-fidelity state discrimination in large two-dimensional (2D) crystals with over 100 trapped ions in a single trapping region, combining a hardware detector and an artificial neural network. A highdata -rate, spatially resolving, single -photon sensitive timestamping detector performs efficient single -shot detection of 2D crystals in a Penning trap, exhibiting rotation at about 25 kHz. We then train an artificial neural network to process the fluorescence photon data in the rest frame of the rotating crystal in order to identify ion locations with a success rate of 90%, accounting for substantial illumination inhomogeneity across the crystal. Finally, employing a time -binned state detection method, we arrive at an average spinstate detection fidelity of 94 (2 )%. This technique can be used to analyze spatial and temporal correlations in arrays of hundreds of trapped -ion qubits.

We present the measurements of individual bound electron g factors of ^{20}Ne^{9+} and ^{22}Ne^{9+} on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(^{20}Ne)=19.992 440 168 77(9)  u, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with m_{e}=5.485 799 090 99(59)×10^{-4}  u as well as a factor of seven improved m(^{22}Ne)=21.991 385 098 2(26)  u.

Atom-interferometric quantum sensors could revolutionize navigation, civil engineering, and Earth observation. However, operation in real-world environments is challenging due to external interference, platform noise, and constraints on size, weight, and power. Here we experimentally demonstrate that tailored light pulses designed using robust control techniques mitigate significant error sources in an atom-interferometric accelerometer. To mimic the effect of unpredictable lateral platform motion, we apply laser-intensity noise that varies up to 20% from pulse-to-pulse. Our robust control solution maintains performant sensing, while the utility of conventional pulses collapses. By measuring local gravity, we show that our robust pulses preserve interferometer scale factor and improve measurement precision by 10× in the presence of this noise. We further validate these enhancements by measuring applied accelerations over a 200 μ g range up to 21× more precisely at the highest applied noise level. Our demonstration provides a pathway to improved atom-interferometric inertial sensing in real-world settings.

We present the measurements of individual bound electron g factors of Ne-20(9+) and Ne-22(9+) on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(Ne-20) = 19.992 440 168 77(9) u, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with m(e) = 5.485 799 090 99(59) x 10(-4) u as well as a factor of seven improved m(22) = 21.991 385 098 2(26) u.

We present the measurements of individual bound electron $g$ factors of $^{20}\text{Ne}^{9+}$ and $^{22}\text{Ne}^{9+}$ on the relative level of $0.1\,\text{parts}$ per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in $m\left(^{20}\text{Ne}\right)=19.992\,440\,168\,77\,(9)\,\text{u}$, which improves the current literature value by a factor of nineteen, disagrees by $4$ standard deviations and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of $0.1\,\text{ppb}$ with $m_{\text{e}}=5.485\,799\,090\,99\,(59) \times 10^{-4}\,\text{u}$ as well as a factor of eight improved $m\left(^{22}\text{Ne}\right)=21.991\,385\,098\,2\,(26)\,\text{u}$.

We present the measurements of individual bound electron $g$ factors of ${^{20}\mathrm{Ne}}^{9+}$ and ${^{22}\mathrm{Ne}}^{9+}$ on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in $m(^{20}\mathrm{Ne})=\phantom{\rule{0ex}{0ex}}19.992\text{ }440\text{ }168\text{ }77(9)\text{ }\text{ }\mathrm{u}$, which improves the current literature value by a factor of 18, disagrees by 4 standard deviations, and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with ${m}_{\mathrm{e}}=5.485\text{ }799\text{ }090\text{ }99(59)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}\text{ }\text{ }\mathrm{u}$ as well as a factor of seven improved $m(^{22}\mathrm{Ne})=21.991\text{ }385\text{ }098\text{ }2(26)\text{ }\text{ }\mathrm{u}$.

We present the measurements of individual bound electron g factors of ^20Ne^9+ and ^22Ne^9+ on the relative level of 0.1 parts per billion. The comparison with theory represents the most stringent test of bound-state QED in strong electric fields. A dedicated mass measurement results in m(^20Ne)=19.992 440 168 77 (9) u, which improves the current literature value by a factor of nineteen, disagrees by 4 standard deviations and represents the most precisely measured mass value in atomic mass units. Together, these measurements yield an electron mass on the relative level of 0.1 ppb with m_e=5.485 799 090 99 (59) × 10^-4 u as well as a factor of eight improved m(^22Ne)=21.991 385 098 2 (26) u.

In this paper, we report on the development of a fast high-voltage switch, which is based on two enhancement mode N-channel silicon carbide metal-oxide-semiconductor field-effect transistors in push-pull configuration. The switch is capable of switching high voltages up to 600 V on capacitive loads with rise and fall times on the order of 10 ns and pulse widths ≥20 ns. Using this switch, it was demonstrated that, from the charge state distribution of bunches of highly charged ions ejected from an electron beam ion trap with a specific kinetic energy, single charge states can be separated by fast switching of the high voltage applied to a Bradbury-Nielsen Gate with a resolving power of about 100.

Helium-3 has nowadays become one of the most important candidates for studies in fundamental physics1-3, nuclear and atomic structure4,5, magnetometry and metrology6, as well as chemistry and medicine7,8. In particular, 3He nuclear magnetic resonance (NMR) probes have been proposed as a new standard for absolute magnetometry6,9. This requires a high-accuracy value for the 3He nuclear magnetic moment, which, however, has so far been determined only indirectly and with a relative precision of 12 parts per billon10,11. Here we investigate the 3He+ ground-state hyperfine structure in a Penning trap to directly measure the nuclear g-factor of 3He+ [Formula: see text], the zero-field hyperfine splitting [Formula: see text] Hz and the bound electron g-factor [Formula: see text]. The latter is consistent with our theoretical value [Formula: see text] based on parameters and fundamental constants from ref. 12. Our measured value for the 3He+ nuclear g-factor enables determination of the g-factor of the bare nucleus [Formula: see text] via our accurate calculation of the diamagnetic shielding constant13 [Formula: see text]. This constitutes a direct calibration for 3He NMR probes and an improvement of the precision by one order of magnitude compared to previous indirect results. The measured zero-field hyperfine splitting improves the precision by two orders of magnitude compared to the previous most precise value14 and enables us to determine the Zemach radius15 to [Formula: see text] fm.

The cyclotron frequency ratio of ^{187}Os^{29+} to ^{187}Re^{29+} ions was measured with the Penning-trap mass spectrometer PENTATRAP. The achieved result of R=1.000 000 013 882(5) is to date the most precise such measurement performed on ions. Furthermore, the total binding-energy difference of the 29 missing electrons in Re and Os was calculated by relativistic multiconfiguration methods, yielding the value of ΔE=53.5(10)  eV. Finally, using the achieved results, the mass difference between neutral ^{187}Re and ^{187}Os, i.e., the Q value of the β^{-} decay of ^{187}Re, is determined to be 2470.9(13) eV.

First ever measurements of the ratios of free cyclotron frequencies of heavy, highly charged ions with Z>50 with relative uncertainties close to 10^{-11} are presented. Such accurate measurements have become realistic due to the construction of the novel cryogenic multi-Penning-trap mass spectrometer PENTATRAP. Based on the measured frequency ratios, the mass differences of five pairs of stable xenon isotopes, ranging from ^{126}Xe to ^{134}Xe, have been determined. Moreover, the first direct measurement of an electron binding energy in a heavy highly charged ion, namely of the 37th atomic electron in xenon, with an uncertainty of a few eV is demonstrated. The obtained value agrees with the calculated one using two independent, different implementations of the multiconfiguration Dirac-Hartree-Fock method. PENTATRAP opens the door to future measurements of electron binding energies in highly charged heavy ions for more stringent tests of bound-state quantum electrodynamics in strong electromagnetic fields and for an investigation of the manifestation of light dark matter in isotopic chains of certain chemical elements.

An experimental realization of a compact, high-power spectral beamsplitter for nearly equal frequencies and identical polarization based on two-beam interference in a free-space Mach-Zehnder interferometer is presented. We demonstrate the power- and cost-efficient generation and subsequent spatial separation of two laser tones from a single sum-frequency-generation stage using double-sideband suppressed-carrier modulation in the infrared, and beam splitting in the visible at high power. The interferometer spectrally splits >98 % of the incident power when accounting for bulk absorption. The beamsplitter can be constructed identically for any power or spectral range required for which suitable optics are available.

State-of-the-art optical clocks 1 achieve precisions of 10 −18 or better using ensembles of atoms in optical lattices 2 , 3 or individual ions in radio-frequency traps 4 , 5 . Promising candidates for use in atomic clocks are highly charged ions 6 (HCIs) and nuclear transitions 7 , which are largely insensitive to external perturbations and reach wavelengths beyond the optical range 8 that are accessible to frequency combs 9 . However, insufficiently accurate atomic structure calculations hinder the identification of suitable transitions in HCIs. Here we report the observation of a long-lived metastable electronic state in an HCI by measuring the mass difference between the ground and excited states in rhenium, providing a non-destructive, direct determination of an electronic excitation energy. The result is in agreement with advanced calculations. We use the high-precision Penning trap mass spectrometer PENTATRAP to measure the cyclotron frequency ratio of the ground state to the metastable state of the ion with a precision of 10 −11 —an improvement by a factor of ten compared with previous measurements 10 , 11 . With a lifetime of about 130 days, the potential soft-X-ray frequency reference at 4.96 × 10 16 hertz (corresponding to a transition energy of 202 electronvolts) has a linewidth of only 5 × 10 −8 hertz and one of the highest electronic quality factors (10 24 ) measured experimentally so far. The low uncertainty of our method will enable searches for further soft-X-ray clock transitions 8 , 12 in HCIs, which are required for precision studies of fundamental physics 6 .

This paper reports on the development and testing of a novel, highly efficient technique for the injection of very rare species into electron beam ion traps (EBITs) for the production of highly charged ions (HCI). It relies on in-trap laser-induced desorption of atoms from a sample brought very close to the electron beam resulting in a very high capture efficiency in the EBIT. We have demonstrated a steady production of HCI of the stable isotope 165Ho from samples of only 1012 atoms (∼300 pg) in charge states up to 45+. HCI of these species can be subsequently extracted for use in other experiments or stored in the trapping volume of the EBIT for spectroscopic measurements. The high efficiency of this technique extends the range of rare isotope HCIs available for high-precision atomic mass and spectroscopic measurements. A first application of this technique is the production of HCI of the synthetic radioisotope 163Ho for a high-precision measurement of the QEC-value of the electron capture in 163Ho within the "Electron Capture in Holmium" experiment [L. Gastaldo et al., J. Low Temp. Phys. 176, 876-884 (2014); L. Gastaldo et al., Eur. Phys. J.: Spec. Top. 226, 1623-1694 (2017)] (ECHo collaboration) ultimately leading to a measurement of the electron neutrino mass with an uncertainty on the sub electronvolt level.

A new experiment is constructed aiming at the first direct high-precision measurement of the helium-3 nuclear magnetic moment with a relative precision of parts-per-billion or better. Methods similar to those used in proton and antiproton magnetic moment measurements are applied. As those techniques rely on the challenging detection of single spin-flips, a novel Penning trap design optimized for nuclear spin-flip detection is developed.