This study explores the excitation and ionization of an atomic beam as a pathway to optimize focused ion beams (FIBs) for high-precision applications. Leveraging the unique advantages of Rydberg excitation followed by field ionization – specifically its ability to minimize velocity and position dispersions – we present a method to generate ion beams with good performance at low energies. A custom Lua program, integrated into the SIMION simulation platform, models the intricate processes of particle distributions, laser excitation, and Rydberg ionization. This integrated approach incorporates essential parameters such as excitation and ionization rates, Stark shifts, Doppler effects, and electric fields, enabling a detailed analysis of ion beam properties. Our simulations demonstrate the influence of critical factors such as the chosen Rydberg state, ionization region characteristics, and velocity dispersions on the final ion beam quality. By optimizing these parameters, we achieve significant reduction of the axial energy spread and the longitudinal extent of the ionization region. This framework bridges theoretical modeling and experimental validation, offering a comprehensive toolkit for the development of next-generation ion sources and advancing FIB technologies across various scientific domains.

Registers of trapped neutral atoms, excited to Rydberg states to induce strong long-distance interactions, are extensively studied for direct applications in quantum computing. Here we present a CCΦ quantum phase gate protocol based on radio-frequency-induced Förster resonant interactions in the array of highly excited Rb87 atoms. The extreme controllability of interactions provided by rf field application enables high-fidelity and robust gate performance for a wide range of parameters of the atomic system, as well as it significantly facilitates the experimental implementation of the gate protocol. Taking into account finite Rydberg states lifetimes, we achieve an average theoretical gate fidelity of 99.27% under room-temperature conditions (improved up to 99.65% in a cryogenic environment), thus showing the protocol compatibility with modern quantum error correction techniques. Published by the American Physical Society 2025

Registers of trapped neutral atoms, excited to Rydberg states to induce strong long-distance interactions, are extensively studied for direct applications in quantum computing. In this regard, new effective approaches to the creation of multiqubit quantum gates arise high interest. Here, we present a novel gate implementation technique based on RF-induced few-body Förster resonances. External radio frequency (RF) control field allows us to manipulate the phase and population dynamics of many-atom system, thus enabling the realization of universal $CCR_{Z}(\phi)$ quantum gates. We numerically demonstrate RF-induced resonant interactions, as well as high-precision three-qubit gates. The extreme controllability of interactions provided by RF makes it possible to implement gates for a wide range of parameters of the atomic system, and significantly facilitates their experimental implementation. For the considered error sources, we achieve theoretical gate fidelities compatible with error correction ($\sim 99.7\%$) using reasonable experimental parameters.

We present a hybrid imaging/timing detector for force sensitive inertial measurements designed for measurements on positronium, the metastable bound state of an electron and a positron, but also suitable for applications involving other low intensity, low energy beams of neutral (antimatter)-atoms, such as antihydrogen. The performance of the prototype detector was evaluated with a tunable low energy positron beam, resulting in a spatial resolution of approximate to <i 12 mm, a detection efficiency of up to 40% and a time-resolution in the order of tens of ns.

New experimental quantum simulation platforms have recently been implemented with divalent atoms trapped in optical tweezer arrays with promising performance. The second valence electron also brings new propects through the so-called Isolated Core Excitation (ICE), however autoionization presents a strong limitation to this use. In this study, we propose and demonstrate a new approach to applying a sizable light shift to a Rydberg state with close-to-resonant ICE while avoiding auto-ionization. In particular, we have investigated ICE of ytterbium atoms in $^1S_0$ Rydberg states. Spectroscopic studies of the induced auto-ionization and the light shift imparted to the Rydberg states are perfectly accounted for with Multi-channel Quantum Defect Theory. Such a control over the inner electron without disturbing the Rydberg electron brings a new tool for the targeted, coherent manipulation of Rydberg states in quantum simulation experiments performed with alkaline-earth atoms.

We have developed an improved scheme of a three-qubit Toffoli gate based on fine structure state changing three-body Stark-tuned Rydberg interaction. This scheme is a substantial improvement of our previous proposal [I.I.Beterov et al., Physical Review A 98, 042704 (2018)]. Due to the use of a different type of three-body F\"orster resonance we substantially simplified the scheme of laser excitation and phase dynamics of collective three-body states. This type of F\"orster resonance exists only in systems with more than two atoms, while the two-body resonance is absent. We reduced the sensitivity of the gate fidelity to fluctuations of external electric field and eliminated the necessity to use external magnetic field for fine tuning of the resonant electric field value, compared to the previous scheme of Toffoli gate based on Rydberg atoms. A gate fidelity of >99% was demonstrated in the calculations.

The primary goal of the AEgIS collaboration at CERN is to measure the gravitational acceleration on neutral antimatter. Positronium (Ps), the bound state of an electron and a positron, is a suitable candidate for a force-sensitive inertial measurement by means of deflectometry/interferometry. In order to conduct such an experiment, the impact position and time of arrival of Ps atoms at the detector must be detected simultaneously. The detection of a low-velocity Ps beam with a spatial resolution of (88 ± 5) μm was previously demonstrated [1]. Based on the methodology employed in [1] and [2], a hybrid imaging/timing detector with increased spatial resolution of about 10 μm was developed. The performance of a prototype was tested with a positron beam. The concept of the detector and first results are presented.

G. Kornakov, M. Auzins, B. Bergmann, P. Burian, G. Bonomi, R. S. Brusa, f ,g A. Camper, R. Caravita, f ,g F. Castelli, j P. Cheinet, R. Ciuryło, D. Comparat, G. Consolati, M. Doser, H. Gjersdal, L. T. Glöggler, Ł. Graczykowski, F. Guatieri, f ,g S. Haider, S. Huck, M. Janik, G. Kasprowicz, G. Khatri, Ł. Kłosowski, L. Lappo, C. Malbrunot, S. Mariazzi, f G. Nebbia, L. Nowak, D. Nowicka, E. Oswald, D. Pagano, L. Penasa, f ,g V. Petracek, M. Piwiński, S. Pospisil, L. Povolo, f F. Prelz, S. Rangwala, B. Rienäcker, A. Rotondi, O. M. Røhne, H. Sandaker, I. Stekl, D. Tefelski, I. C. Tietje, M. Volponi, f ,g,n T. Wolz, M. Zawada, C. Zimmer and N. Zurlo

Low-temperature antihydrogen atoms are an effective tool to probe the validity of the fundamental laws of Physics, for example the Weak Equivalence Principle (WEP) for antimatter, and -generally speaking- it is obvious that colder atoms will increase the level of precision. After the first production of cold antihydrogen in 2002 [1], experimental efforts have substantially progressed, with really competitive results already reached by adapting to cold antiatoms some well-known techniques pre- viously developed for ordinary atoms. Unfortunately, the number of antihydrogen atoms that can be produced in dedicated experiments is many orders of magnitude smaller than of hydrogen atoms, so the development of novel techniques to enhance the production of antihydrogen with well defined (and possibly controlled) conditions is essential to improve the sensitivity. We present here some experimental results achieved by the AEgIS Collaboration, based at the CERN AD (Antiproton Decelerator) on the production of antihydrogen in a pulsed mode where the production time of 90% of atoms is known with an uncertainty of ~ 250 ns [2]. The pulsed antihydrogen source is generated by the charge-exchange reaction between Rydberg positronium (Ps*) and an antiproton (p¯): p¯ + Ps* → H¯* + e−, where Ps* is produced via the implantation of a pulsed positron beam into a mesoporous silica target, and excited by two consecutive laser pulses, and antiprotons are trapped, cooled and manipulated in Penning-Malmberg traps. The pulsed production (which is a major milestone for AEgIS) makes it possible to select the antihydrogen axial temperature and opens the door for the tuning of the antihydrogen Rydberg states, their de-excitation by pulsed lasers and the manipulation through electric field gradients. In this paper, we present the results achieved by AEgIS in 2018, just before the Long Shutdown 2 (LS2), as well as some of the ongoing improvements to the system, aimed at exploiting the lower energy antiproton beam from ELENA [3].

We study isolated core excitation of ultracold ytterbium Rydberg atoms of high orbital angular momentum quantum number $\ensuremath{\ell}$. Measurements were performed on the $6{s}_{1/2}40\ensuremath{\ell}\ensuremath{\rightarrow}6{p}_{1/2}40\ensuremath{\ell}$ transition with $\ensuremath{\ell}=5--9$. The extracted energy shifts and autoionization rates are in good agreement with a model based on independent electrons, taking interactions into account in a perturbative approach. We reveal a slow decrease in the autoionization rates with $\ensuremath{\ell}$, explained by the strong coupling of the $6{p}_{1/2}n\ensuremath{\ell}$ autoionizing state with the $5{d}_{3/2}\ensuremath{\epsilon}{\ensuremath{\ell}}^{\ensuremath{'}}$ continua compared to previously studied divalent atoms.

Three body resonant interactions between Rydberg atoms are considered in order to perform few-body quantum gates. So far, the resonances found in cesium or rubidium atoms relied on an adjacent two-body resonance which ceases to exist for principal quantum numbers above $n \simeq 40$. We have proposed recently a new class of 3-body interaction resonances in alkali-metal Rydberg atoms [P. Cheinet \textit{et al.}, Quant. Elect. \textbf{50}, 213 (2020)], which circumvienes this limit. We investigate here the relative strength between this new class of 3-body interaction resonance and quasi-forbidden 2-body interaction resonances in rubidium and cesium Rydberg atoms. We then identify the best case scenario for detecting and using this 3-body interaction.

A main scientific goal of theAEg over bar ISgon antihydrogen. The Weak Equivalence Principle is a foundation of General Relativity. It has been extensively tested with ordinary matter but very little is known about the gravitational interaction between matter and antimatter. Antihydrogen is produced inAEg over bar IS<ivia resonant charge-exchange reaction between cold Rydberg-excited positronium and cooled down antiprotons. The achievements for the development of a pulsed cold antihydrogen source are presented. Large number of antiprotons, necessary for a significant production rate of antihydrogen, are captured, accumulated, compressed and cooled over an extended period of time. Positronium (Ps) is formed through e(+)-Ps conversion in a silica porous target at 10 K temperature in a reflection geometry inside the main apparatus. The so-formed Ps cloud is then laser-excited to Rydberg levels, for the first time in a 1 T magnetic field. Consequently, a detailed characterization of the Ps source for antihydrogen production in magnetic field needed to be performed. Several detection techniques are extensively used to monitor antiproton and positron manipulations in the formation process of antihydrogen inside the main apparatus. Positronium detection techniques underwent extensive improvements in sensitivity during the last antiproton run. At the same time, major efforts to improve integrate and commission the detectors sensitive to antihydrogen production took place.

The three-body Forster resonances 3xnP(3/2)(vertical bar M vertical bar) -> nS(1/2) + (n + 1)S-1/2 + nP(3/2)(vertical bar M*vertical bar), controlled by a constant electric field, were realised earlier by the authors in an ensemble of several cold Rydberg Rb atoms. One of the drawbacks of such resonances for potential application in three-qubit quantum gates is the proximity of the two-body Forster resonance 2xnP(3/2) -> nS(1/2) + (n + 1)S-1/2, as well as the possibility of their implementation only for states with values of the principal quantum numbers n <= 38. A three-body resonance of a new type, 3xnP(3/2) -> nS(1/2) + (n + 1)S-1/2 + nP(1/2), which can be realised for arbitrary n, is proposed and analysed. Its specific feature is also that the third atom transits into a state with a different total angular momentum J = 1/2, which has no Stark structure, so that the two-body resonance is completely absent. Numerical calculations showed that for not too strong interaction, it is possible to observe coherent three-body oscillations of the populations of collective states, which is of interest for developing new schemes of three-qubit quantum gates controlled by an electric field.

We propose a scheme of fast three-qubit Toffoli quantum gate for ultracold neutral-atom qubits. The scheme is based on the Stark-tuned three-body Förster resonances, which we have observed in our recent experiment [D.B.Tretyakov et al., Phys.Rev.Lett. 119, 173402 (2017)]. The three-body resonance corresponds to a transition when the three interacting atoms change their states simultaneously, and it occurs at a different dc electric field with respect to the two-body Förster resonance. A combined effect of three-body and two-body Förster interactions in external electric and magnetic fields near the three-body resonance results in complex coherent behavior of the populations and phases of collective states of a three-atom system. We have found that it is possible to obtain experimental conditions suitable to implement three-qubit Toffoli gate with 96.8\% fidelity and less than 3~$\mu$s duration.

A gas of cold Rydberg atoms generally interacts through 2-body van der Waals interaction. When applying an electric field, it has long been observed that resonant dipole-dipole interactions can arise [1]. More recently we have demonstrated the possibility to find resonant processes involving 3 Rydberg atoms [2]. Although this experiment was performed with cesium atoms, we argued that similar 3-body interaction resonances should be observed in other atoms. We have now observed it in rubidium [3] with a small controlled number of atoms i = 2-5. This not only demonstrated the general nature of the process, but also the absence of signature of the three-body Förster resonances for exactly two interacting Rydberg atoms. As the observed three-body resonance appears at a different dc electric field with respect to the two-body resonance, it represents an effective three-body operator, which can be used to directly control the three-body interactions. This can be especially useful in quantum simulations and quantum information processing with neutral atoms in optical lattices.

We measure the coherent scattering of low-intensity, near-resonant light by a cloud of laser-cooled two-level rubidium atoms with a size comparable to the wavelength of light. We isolate a two-level atomic structure by applying a 300-G magnetic field. We measure both the temporal and the steady-state coherent optical response of the cloud for various detunings of the laser and for atom numbers ranging from 5 to 100. We compare our results to a microscopic coupled-dipole model and to a multimode, paraxial Maxwell-Bloch model. In the low-intensity regime, both models are in excellent agreement, thus validating the Maxwell-Bloch model. Comparing to the data, the models are found in very good agreement for relatively low densities (n/k(3) less than or similar to 0.1), while significant deviations start to occur at higher density. This disagreement indicates that light scattering in dense, cold atomic ensembles is still not quantitatively understood, even in pristine experimental conditions.

Measurements of high-lying even-parity $6sns\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}$ and $6snd\phantom{\rule{0.16em}{0ex}}{}^{1,3}{D}_{2}$ levels of neutral $^{174}\mathrm{Yb}$ are presented in this paper. Spectroscopy is performed with a two-step laser excitation from the ground state $4{f}^{14}6{s}^{2}\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}$, and the Rydberg levels are detected by using the field ionization method. Additional two-photon microwave spectroscopy is used to improve the relative energy accuracy where possible. The spectroscopic measurements are complemented by a multichannel-quantum-defect-theory (MQDT) analysis for the $J=0$ and the two-coupled $J=2$ even-parity series. We compare our results with the previous analysis of Aymar, D\'ebarre, and Robaux [J. Phys. B: At. Mol. Phys. 13, 1089 (1980)] and analyze the observed differences. From the MQDT models, a revised value for the first ionization limit ${I}_{6s}=50443.07041(25)\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ is proposed for $^{174}\mathrm{Yb}$.

Atom interferometry has hugely benefitted from advances made in cold atom physics over the past twenty years, and ultra-precise quantum sensors are now available for a wide range of applications [1]. In particular, cold atom interferometers have shown excellent performances in the field of acceleration and rotation measurements [2,3], and are foreseen as promising candidates for navigation, geophysics, geo-prospecting and tests of fundamental physics such as the Universality of Free Fall (UFF). In order to carry out a test of the UFF with atoms as test masses, one needs to compare precisely the accelerations of two atoms with different masses as they fall in the Earth's gravitational field. The sensitivity of atom interferometers scales like the square of the time during which the atoms are in free fall, and on ground this interrogation time is limited by the size of the experimental setup to a fraction of a second. Sending an atom interferometer in space would allow for several seconds of excellent free-fall conditions, and tests of the UFF could be carried out with precisions as low as 10-15 [4]. However, cold atoms experiments rely on complex laser systems, which are needed to cool down and manipulate the atoms, and these systems are usually very sensitive to temperature fluctuations and vibrations. In addition, when operating an inertial sensor, vibrations are a major issue, as they deteriorate the performances of the instrument. This is why cold atom interferometers are usually used in ground based facilities, which provide stable enough environments. In order to carry out airborne or space-borne measurements, one has to design an instrument which is both compact and stable, and such that vibrations induced by the platform will not deteriorate the sensitivity of the sensor. We report on the operation of an atom interferometer on board a plane carrying out parabolic flights (Airbus A300 Zero-G, operated by Novespace). We have constructed a compact and stable laser setup, which is well suited for onboard applications. Our goal is to implement a dual-species Rb-K atom interferometer in order to carry out a test of the UFF in the plane. In this perspective, we are designing a dual-wavelength laser source, which will enable us to cool down and coherently manipulate the quantum states of both atoms. We have successfully tested a preliminary version of the source and obtained a double species magneto-optical trap (MOT).

Three-body Förster resonances at long-range interactions of Rydberg atoms were first predicted and observed in Cs Rydberg atoms by Faoro et al. [Nat. Commun. 6, 8173 (2015)NCAOBW2041-172310.1038/ncomms9173]. In these resonances, one of the atoms carries away an energy excess preventing the two-body resonance, leading thus to a Borromean type of Förster energy transfer. But they were in fact observed as the average signal for the large number of atoms N≫1. In this Letter, we report on the first experimental observation of the three-body Förster resonances 3×nP_{3/2}(|M|)→nS_{1/2}+(n+1)S_{1/2}+nP_{3/2}(|M^{*}|) in a few Rb Rydberg atoms with n=36, 37. We have found here clear evidence that there is no signature of the three-body Förster resonance for exactly two interacting Rydberg atoms, while it is present for N=3-5 atoms. This demonstrates the assumption that three-body resonances can generalize to any Rydberg atom. As such resonance represents an effective three-body operator, it can be used to directly control the three-body interactions in quantum simulations and quantum information processing with Rydberg atoms.