An apparatus has been developed for studying the interaction of Rydberg atoms with surfaces, particularly the perturbation of Rydberg states by a nearby surface and the distance from the surface at which resonance ionization occurs. For this purpose, a source of metastable Xe(3P 0,2) atoms was constructed and characterized. Using single photon laser excitation from the 6s'[1/2]0 state, the nf[3/2]1 Rydberg series for n = 16--20 has been observed with signals well above the background. Measurements of the energy levels of these Rydberg states has identified systematic errors in quoted energy levels from earlier work. The isotopic structure of the 20f Rydberg state was resolved, and the effect of Rydberg excitation in an electric field was investigated. Studies are underway to better understand the behavior of Xe(nf) Rydberg atoms in an electric field. This information will be used in subsequent experiments to study Rydberg-surface interactions.
An apparatus has been developed for studying the interaction of Rydberg atoms with surfaces, particularly the perturbation of Rydberg states by a nearby surface and the distance from the surface at which resonance ionization occurs. For this purpose, a source of metastable Xe(3P 0,2) atoms was constructed and characterized. Using single photon laser excitation from the 6s'[1/2]0 state, the nf[3/2]1 Rydberg series for n = 16--20 has been observed with signals well above the background. Measurements of the energy levels of these Rydberg states has identified systematic errors in quoted energy levels from earlier work. The isotopic structure of the 20f Rydberg state was resolved, and the effect of Rydberg excitation in an electric field was investigated. Studies are underway to better understand the behavior of Xe(nf) Rydberg atoms in an electric field. This information will be used in subsequent experiments to study Rydberg-surface interactions.
Highly excited (Rydberg) atoms have exaggerated properties making them extremely sensitive to external electromagnetic fields and interacting strongly with their environment. Atomic vapor cells represent an attractive platform for studying Rydberg atoms and fabricating quantum devices. For example, Rydberg atoms in vapor cells have been used as sensitive detectors of electric fields of frequencies ranging from DC up to the THz range but also as single photon sources for quantum technology applications exploiting collective phenomena due to the Rydberg blockade effect [1]. Rydberg atoms also find applications in fundamental physics, in particular for the measurement of dispersive interactions of the Casimir-Polder type (atom-surface interactions) [2]. One major advantage of Rydberg atoms is that they expose limitations in the traditional perturbative approach of Casimir-Polder (CP) theory [3, 4]. Indeed, in the extreme near-field, the dipole approximation breaks down and higher-order terms need to be considered. We report on extensive experimental measurements of the Rydberg-surface interaction using spectroscopy in cesium vapor nanocells of a thickness ranging roughly from 200-700nm, as well as selective reflection spectroscopy on a macroscopic cesium all-sapphire cell. Atoms are first excited to the Cs(6P) level with a 894nm pump laser and subsequently a green laser ≈ 510nm probes Rydberg nD or nS states, where the principal quantum number n ranges between 15-17. Our experiments evidence the dipole-dipole term of the Casimir-Polder interaction providing a measurement of the C3 coefficient for cesium Rydberg states. Furthermore, our experiment clearly evidences an additional interaction that induces shifts and broadens the linewidth of the probed transitions in the vicinity of the dielectric windows of our cells. We believe that this interaction is due to electric fields that are either generated by patch charges (trapped on the surface or induced by the excitation lasers), or by cesium adsorbants. We show that the different polarizability (of opposing sign) between S and D Rydberg states can be exploited to extract quantitative measurements of the strength and distance scaling (z-dependence) of such parasitic electrostatic interactions.Our experiments suggest that the sensitivity of Rydberg atoms to external electric fields could provide a unique tool for probing electrostatic interactions in the vicinity of surfaces. This could allow systematic error corrections in Casimir-Polder experiments with excited or even ground state atoms that aim at putting bounds on the existence of non-Newtonian gravity [5]. We are currently exploring the possibility of coating the internal window interfaces with conducting 2D material such as graphene to reduce the influence of parasitic charges. This could allow us to probe atoms closer to the surface, where quadrupole interactions could be experimentally attainable for the first time [4].References[1] H. Kubler, J. P. Shaffer, T. Baluktsian, R. Loew, T. Pfau, Nat. Photon., 4, 112–116 (2013).[2] V. Sandoghdar et al., Phys. Rev. Lett 68, 3432–3435 (1993).[3] J. A. Crosse et al., Phys. Rev. A 82, 3010901 (2010).[4] B. Dutta et al., Phys. Rev. Res. 6, L022035 (2024).[5] A. Laliotis, B-S. Lu, M. Ducloy, D. Wilkowski, AVS Quantum Sci. 3, 043501 (2021).
We demonstrate spatially resolved, coherent excitation of Rydberg atoms on an atom chip. Electromagnetically induced transparency (EIT) is used to investigate the properties of the Rydberg atoms near the gold-coated chip surface. We measure distance-dependent shifts (10 MHz) of the Rydberg energy levels caused by a spatially inhomogeneous electric field. The measured field strength and distance dependence is in agreement with a simple model for the electric field produced by a localized patch of Rb adsorbates deposited on the chip surface during experiments. The EIT resonances remain narrow (<4 MHz) and the observed widths are independent of atom-surface distance down to 20 $\ensuremath{\mu}$m, indicating relatively long lifetime of the Rydberg states. Our results open the way to studies of dipolar physics, collective excitations, quantum metrology, and quantum information processing involving interacting Rydberg excited atoms on atom chips.
This thesis reports the first controlled study of the interactions of Rydberg atoms with a metal surface. In these experiments, a collimated beam of potassium Rydberg atoms is directed at a plane surface at near grazing incidence. Positive ions formed by surface ionization are attracted to the surface by their image charge, which is counterbalanced by an external electric field applied perpendicular to the surface. The ions are detected by a position-sensitive detector (PSD). At some critical value of the external field, the ion trajectories just miss the surface, suggesting that analysis of the dependence of the ion signals on external electric field can be used to determine the distance from the surface at which ionization occurs. This distance, and thus the corresponding critical electric field, is expected to be n-dependent. Experimentally, however, it was observed that the ion signal had a sudden n-independent onset when only a small positive perpendicular electric field was applied at the surface. This observation requires, surprisingly, that the ions produced by surface ionization can readily escape from the surface. The data do, however, show that Rydberg atoms are efficiently ionized in collisions with the surface. This process may provide a useful new detection technique for Rydberg atoms.
The ionization of xenon Rydberg atoms at metallic surfaces is examined. The data show that, when the effects of stray electric "patch" fields present on the surface are taken into account, ionization is well described by a simple over-the-barrier model. The patch fields are determined from direct measurements of the potential variations across the target surfaces using Kelvin probe force microscopy. Monte Carlo techniques are used to model the atom-surface interaction. The results confirm the important role that patch fields can play during Rydberg atom-surface interactions and suggest that such interactions can provide a sensitive probe of stray fields at surfaces. To demonstrate this, measurements of the threshold conditions required to observe ions resulting from surface ionization are used to estimate how large such stray fields can be. The data show that the stray fields can be sizable, as large as ∼ 10 3 V · cm -1 100 nm from the surface and ∼ 10 V · cm -1 500 nm from the surface, and illustrate the potential of Rydberg atoms for detecting and characterizing surface electric fields. Methods to enhance the surface ionization signal using electrode arrays patterned on a surface are investigated. Simulations show that bias voltages applied to a series of parallel wires comprised of two interleaved comb-shaped electrodes can have a dramatic impact on ion collection efficiency. It is suggested that such a surface can be used to efficiently collect low- n Rydberg atoms ( n [Special characters omitted.] 10). Significant progress towards fabrication of a functioning surface of 1 μm wide wires with 1 μm spacing is documented.
The behavior of Rydberg atoms near metal surfaces in the presence of an external electric field has been examined theoretically to evaluate their potential use as an experimental probe of electron tunneling processes at surfaces. These ab initio calculations reveal strong hybridization that leads to a shift and broadening of the Rydberg levels that depend sensitively on the atom-surface separation and the strength of the applied electric field. A range of external fields exists, however, for which the Rydberg atoms ionize at sufficiently large atom-surface separations that, even in the presence of image charge attraction, the resulting positive ions can escape the surface and provide an experimentally observable signal. \textcopyright{} 1996 The American Physical Society.
The design, construction and characterization of an atom chip apparatus for cold Rydberg atom experiments with 87Rb is presented. The apparatus is designed to investigate interactions between Rydberg atoms and the nearby chip surface, as well as the dynamics of Rydberg atoms in a double well. The proposed interrogation scheme is Rydberg electromagnetically induced transparency (Rydberg EIT). Magnetic trapping potentials used to load the chip with atoms are calculated. The atom number and temperature during various phases of the loading sequence are measured using absorption imaging. The room-temperature 4-level ladder-type Rydberg EIT system, in which the 3-level Rydberg EIT system is coupled via microwaves to a second Rydberg state, is investigated experimentally. EIT transmission spectra for different microwave powers and different polarizations of optical fields and microwaves are presented. It is shown that, to explain the observed polarization effects in the probe transmission lineshape, all magnetic sublevels, including the hyperfine structure of both Rydberg levels, have to be taken into account. The corresponding 52-level theory is discussed. Calculations of long-range multipolar Rydberg-atom Rydberg-atom interaction potentials are also presented and discussed.