We report the trapping and continuous monitoring of a cloud of antiprotons (\pbar{}) for 614 days in the BASE reservoir trap at CERN, representing the longest confinement of antimatter achieved to date. The experiment is operated at an exceptionally low particle-loss rate of less than one antiproton per month, with intervals approaching up to five months without a single loss, and demonstrating one year of continuous experiment operation within which only three particles were consumed. This unprecedented stability establishes a new paradigm for high-precision studies of exotic and ultra-rare charged particles. Our approach is readily extendable to other species, including highly charged ions and prospective antimatter systems such as $\overline{\mathrm{H}}_2^-$, $\overline{\mathrm{H}}^+$, and $\overline{\mathrm{d}}$. By analyzing all BASE reservoir trap data collected since 2014, we set a five-fold improved lower bound on the directly constrained antiproton lifetime. Beyond its fundamental implications, this advance enables future transport and precision measurements on \pbar{} and other exotic ions in dedicated offline laboratories, opening new frontiers in antimatter research.

Magnetic moments of bound-electron systems are a sensitive tool for testing fundamental interactions. The g factors of lithium-like ions have been rigorously studied in recent years, enabling insights into the relativistic interelectronic effects. In this work, we present the g-factor measurement of lithium-like tin, accurate to 0.5 parts per billion, as well as ab initio theoretical calculations that include an advanced treatment of the interelectronic interaction. We further improved the prediction by using the experimental result for the hydrogen-like tin g factor, inferring from it the unknown higher-order quantum electrodynamic (QED) effects. The observed agreement independently confirms the revised theory at a previously inaccessible high atomic number Z of 50, where QED effects are considerably larger.

Um die elektromagnetische Wechselwirkung zu testen, wurde das magnetische Moment des gebundenen Elektrons von lithiumähnlichem Zinn zum ersten Mal mit höchster Präzision vermessen. Die Übereinstimmung auf mehr als sieben Nachkommastellen mit der ebenfalls verbesserten theoretischen Vorhersage bestätigt das Standardmodell.

In this work, we demonstrate a new method for quantum state control and nondestructive internal quantum state readout of a single HD^{+} ion in the rovibrational ground state in a Penning trap. Furthermore, we demonstrate a measurement of the magnetic trapping field with the same ion to sub-ppb uncertainty. This could enable nondestructive, high-precision spectroscopy of the hyperfine, Zeeman, and rovibrational level structure of single molecular ions. In particular, this technique can be applied to H_{2}^{+} as well as to its antimatter equivalent, H[over ¯]_{2}^{-}, with the potential for high-precision tests of charge-parity-time reversal symmetry beyond current sensitivities [Phys. Scr. T 1995, 423 (1995)PHSTBO0031-894910.1088/0031-8949/1995/T59/060, Phys. Rev. A 98, 010101 (2018)PLRAAN2469-992610.1103/PhysRevA.98.010101].

In the Alphatrap experiment, the g factor of boronlike ^{118}Sn^{45+} has been measured with a 0.5 ppb uncertainty. This is the first high-precision measurement of the g factor of a heavy boronlike ion. The measured value of 0.6 447 038 265(4) is consistent with the presented ab initio state-of-the-art theory calculations, which predict a value of 0.64 470 29(8). So far, the only boronlike ion of which the g factor was measured with high precision has been ^{40}Ar^{13+}. The measurement presented here therefore tests quantum electrodynamics as well as many-electron interactions at much higher Z. Furthermore, we discuss the potential for an independent determination of the fine-structure constant α, which can be achieved with a specific difference of g factors, combining the presented results with the recent electron g-factor measurement of hydrogenlike tin.

Inner-shell electrons naturally sense the electric field close to the nucleus, which can reach extreme values beyond 10 15 V cm −1 for the innermost electrons 1 . Especially in few-electron, highly charged ions, the interaction with the electromagnetic fields can be accurately calculated within quantum electrodynamics (QED), rendering these ions good candidates to test the validity of QED in strong fields. Consequently, their Lamb shifts were intensively studied in the past several decades 2 , 3 . Another approach is the measurement of gyromagnetic factors ( g factors) in highly charged ions 4 – 7 . However, so far, either experimental accuracy or small field strength in low- Z ions 5 , 6 limited the stringency of these QED tests. Here we report on our high-precision, high-field test of QED in hydrogen-like 118 Sn 49+ . The highly charged ions were produced with the Heidelberg electron beam ion trap (EBIT) 8 and injected into the ALPHATRAP Penning-trap setup 9 , in which the bound-electron g factor was measured with a precision of 0.5 parts per billion (ppb). For comparison, we present state-of-the-art theory calculations, which together test the underlying QED to about 0.012%, yielding a stringent test in the strong-field regime. With this measurement, we challenge the best tests by means of the Lamb shift and, with anticipated advances in the g -factor theory, surpass them by more than an order of magnitude.

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.

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.

Quantum electrodynamics (QED) is one of the most fundamental theories of physics and has been shown to be in excellent agreement with experimental results 1 – 5 . In particular, measurements of the electron’s magnetic moment (or g factor) of highly charged ions in Penning traps provide a stringent probe for QED, which allows testing of the standard model in the strongest electromagnetic fields 6 . When studying the differences between isotopes, many common QED contributions cancel owing to the identical electron configuration, making it possible to resolve the intricate effects stemming from the nuclear differences. Experimentally, however, this quickly becomes limited, particularly by the precision of the ion masses or the magnetic field stability 7 . Here we report on a measurement technique that overcomes these limitations by co-trapping two highly charged ions and measuring the difference in their g factors directly. We apply a dual Ramsey-type measurement scheme with the ions locked on a common magnetron orbit 8 , separated by only a few hundred micrometres, to coherently extract the spin precession frequency difference. We have measured the isotopic shift of the bound-electron g factor of the isotopes 20 Ne 9+ and 22 Ne 9+ to 0.56-parts-per-trillion (5.6 × 10 −13 ) precision relative to their g factors, an improvement of about two orders of magnitude compared with state-of-the-art techniques 7 . This resolves the QED contribution to the nuclear recoil, accurately validates the corresponding theory and offers an alternative approach to set constraints on new physics.

In article number 2100029, Bingsheng Tu and co-workers present a novel scheme that allows to efficiently cool arbitrary ions by coupling them to a directly laser cooled ion in a separate Penning trap. The authors' results demonstrate how a common tank circuit can drastically enhance the coupling, resulting in the expected avoided-crossing behavior of the two ions. This technique holds promise to enable millikelvin cooling of arbitrary ions in Penning traps.

The coupling of the motion of two ion species in separate Penning traps via a common tank circuit is discussed. The enhancement of the coupling assisted by the tank circuit is demonstrated by an avoided crossing behavior measurement of the motional modes of two coupled ions. An intermittent laser cooling method for sympathetic cooling is proposed and a theoretical description is provided. The technique enables tuning of the coupling strength between two ion species in separate traps and thus allows for efficient sympathetic cooling of an arbitrary type of single ion for high‐precision Penning‐trap experiments.

We present a novel ion trap fabrication method enabling the realization of multilayer ion traps scalable to an in principle arbitrary number of metal-dielectric levels. We benchmark our method by fabricating a multilayer ion trap with integrated three-dimensional microwave circuitry. We demonstrate ion trapping and microwave control of the hyperfine states of a laser cooled ^9Be^+ ion held at a distance of 35μm above the trap surface. This method can be used to implement large-scale ion trap arrays for scalable quantum information processing and quantum simulation.

A superconducting self-shielding three-solenoid system with an adjustable shielding factor is developed, implemented, and characterized using a single antiproton in a Penning trap. With the tuned system, we suppress external magnetic field disturbances by up to a factor of 225 +/- 15, allowing antiproton-to-proton charge-to-mass ratio comparisons with fourfold reduced frequency fluctuations and antiproton magnetic moment determinations with tenfold reduced uncertainty.

Microwave trapped-ion quantum logic gates avoid spontaneous emission as a fundamental source of decoherence. However, microwave two-qubit gates are still slower than laser-induced gates and hence more sensitive to fluctuations and noise of the motional mode frequency. We propose and implement amplitude-shaped gate drives to obtain resilience to such frequency changes without increasing the pulse energy per gate operation. We demonstrate the resilience by noise injection during a two-qubit entangling gate with ^{9}Be^{+} ion qubits. In the absence of injected noise, amplitude modulation gives an operation infidelity in the 10^{-3} range.

We report on the first detailed study of motional heating in a cryogenic Penning trap using a single antiproton. Employing the continuous Stern-Gerlach effect we observe cyclotron quantum transition rates of 6(1)  quanta/h and an electric-field noise spectral density below 7.5(3.4)×10^{-20}  V^{2} m^{-2} Hz^{-1}, which corresponds to a scaled noise spectral density below 8.8(4.0)×10^{-12}  V^{2} m^{-2}, results which are more than 2 orders of magnitude smaller than those reported by other ion-trap experiments.