The Casimir-Polder interaction between atoms and macroscopic surfaces is a fundamental prediction of quantum electrodynamics of importance for precision measurements, quantum technologies and our understanding of the electromagnetic properties of materials. In the near field, Casimir-Polder interactions are described as the interaction of the fluctuating atomic dipole with its surface-induced image, which evolves as −C3/z3 where z is the atom-surface distance and C3 is the van derWaals coefficient. In this thesis, we study boththeoretically and experimentally the Casimir-Polder interaction between a highly excited caesium atom (Rydberg atom) and a dielectric surface. Our theoretical study extends previous studies to include higher-order terms in the atom-surface interaction, beyond the dipole-dipole interaction term investigated in the seminal work of Casimir and Polder. In particular, we include quadrupole-quadrupole and dipole-octupole interaction terms with a distance dependence of −C5/z5 giving explicit calculations of the C5 coefficients for most common alkali atoms. We also describe a new selective reflection experiment probing Cs Rydberg atoms (15 − 17D3/2 and 16 − 17S1/2) at nanometric distances away from a sapphire surface. The experiment is performed in an all-sapphire vapour cell using stepwise excitation spectroscopy that includes a pumping step at 6S1/2 → 6P1/2 (894nm) and a selective reflection probing step at 6P1/2 → nS1/2,nD3/2 with n = 15 - 17 (∼ 510nm). To analyze our experimental spectra, we extend selective reflection theory beyond the infinite Doppler approximation, including in our analysis the Maxwell-Boltzmann distribution of atomic velocities. Fitting our theoretical lineshape model to our experimental spectra allows us to extract the C3 van der Waals coefficient for the probed caesium excited states. This C3 measurement exceeds the theoretical predictions of Casimir-Polder theory by a factor of about 1.5 - 2, depending on the probed state. Finally, we describe a new thin-cell experiment that aims to illuminate the reported disagreement between theory and experiment for the C3 coefficient and provide a first experiment
The Casimir-Polder interaction between atoms and macroscopic surfaces is a fundamental prediction of quantum electrodynamics of importance for precision measurements, quantum technologies and our understanding of the electromagnetic properties of materials. In the near field, Casimir-Polder interactions are described as the interaction of the fluctuating atomic dipole with its surface-induced image, which evolves as −C3/z3 where z is the atom-surface distance and C3 is the van derWaals coefficient. In this thesis, we study boththeoretically and experimentally the Casimir-Polder interaction between a highly excited caesium atom (Rydberg atom) and a dielectric surface. Our theoretical study extends previous studies to include higher-order terms in the atom-surface interaction, beyond the dipole-dipole interaction term investigated in the seminal work of Casimir and Polder. In particular, we include quadrupole-quadrupole and dipole-octupole interaction terms with a distance dependence of −C5/z5 giving explicit calculations of the C5 coefficients for most common alkali atoms. We also describe a new selective reflection experiment probing Cs Rydberg atoms (15 − 17D3/2 and 16 − 17S1/2) at nanometric distances away from a sapphire surface. The experiment is performed in an all-sapphire vapour cell using stepwise excitation spectroscopy that includes a pumping step at 6S1/2 → 6P1/2 (894nm) and a selective reflection probing step at 6P1/2 → nS1/2,nD3/2 with n = 15 - 17 (∼ 510nm). To analyze our experimental spectra, we extend selective reflection theory beyond the infinite Doppler approximation, including in our analysis the Maxwell-Boltzmann distribution of atomic velocities. Fitting our theoretical lineshape model to our experimental spectra allows us to extract the C3 van der Waals coefficient for the probed caesium excited states. This C3 measurement exceeds the theoretical predictions of Casimir-Polder theory by a factor of about 1.5 - 2, depending on the probed state. Finally, we describe a new thin-cell experiment that aims to illuminate the reported disagreement between theory and experiment for the C3 coefficient and provide a first experiment
The Casimir-Polder interaction between atoms and macroscopic surfaces is a fundamental prediction of quantum electrodynamics of importance for precision measurements, quantum technologies and our understanding of the electromagnetic properties of materials. In the near field, Casimir-Polder interactions are described as the interaction of the fluctuating atomic dipole with its surface induced image, which evolves as -C3/z3 where z is the atom-surface distance and C3 is the van der Waals coefficient. In this thesis, we study both theoretically and experimentally the Casimir-Polder interaction between a highly excited cesium atom (Rydberg atom) and a dielectric surface. Our theory extends previous studies to[3]include higher-order terms in the atom-surface interaction, beyond the dipole-dipole interaction term investigated in the seminal work of Casimir and Polder. In particular, we include quadrupole-quadrupole and dipole-octupole interaction terms with a distance dependence of ?C5/z5 giving explicit calculations of the C5 coefficients for most common alkali atoms. We also describe a new selective reflection experiment probing Cs Rydberg atoms (15-17D3/2 and 16-17S1/2) at nanometric distances away from a sapphire surface. The experiment is performed in an all-sapphire vapour cell using stepwise excitation spectroscopy that includes a pumping step at 6S1/2?6P1/2 (894nm) and a selective reflection probing step at 6P1/2?nS1/2 , nD3/2 with n=15-17 (~510nm). In order to analyze our experimental spectra, we extend selective reflection theory beyond the infinite Doppler approximation, including in our analysis the Maxwell-Boltzmann distribution of atomic velocities. Fitting our experimental spectra with our theoretical models allows us to extract the C3 van der Waals coefficient for the probed cesium excited states. The experimental results exceed our theoretical predictions (by a factor of about 1.5-2, depending on the probed state). Finally, we describe a new thin-cell experiment that aims to illuminate the reported disagreement between theory and experiment for the C3 coefficient and provide a first experimental measurement of the C5 coefficient (experimental study of higher-order 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).
The modification of quantum fluctuations by a surface of finite reflectivity shifts the energy levels of atoms and changes their radiative properties (Casimir-Polder effect). At nanometric distances away from a surface (near field), the Casimir-Polder energy shift is given by −C3/z3 (where C3 is the van der Waals coefficient and z is the atom-surface distance) corresponding to the interaction of the fluctuating atomic dipole with its surface induced image. Near field Rydberg-surface interactions are of fundamental interest because the atomic size, scaling as n∗2 (where n∗ is the principle quantum number corrected by the quantum defect), is no longer negligible compared to the atom-surface separation, z. In this case, the dipole approximation, (−C3/z3 law of interaction), is no longer valid and higher-order terms, corresponding to the interaction of the fluctuation quadrupole with its own image, need to be taken into account. Quadrupole interaction terms in the atom-surface interaction manifest themselves with a novel distance dependence of z5 that has not been experimentally investigated yet1. Casimir-Polder experiments were first performed with low-lying Rydberg states (n= 10-14), demonstrating the −C3/z3 law of interaction2. Nevertheless, more recent experiments with high-lying rubidium Rydbergs (n=32-43)3 were not in agreement with Casimir-Polder theory thus highlighting the need for further experimental studies.
Probing caesium Rydberg atoms close to a sapphire surface L’interaction Casimir-Polder entre un atome et une surface macroscopique est une prédiction fondamentale de l’électrodynamique quantique, importante pour les mesures de précision, les technologies quantiques et notre compréhension des propriétés électromagnétiques des matériaux. En champ proche, les interactions Casimir-Polder sont décrites comme l’interaction du dipôle atomique fluctuant avec son image induite par la surface, qui évolue comme -C3/z3, où z est la distance atome-surface et C3 le coefficient de van der Waals. Dans cette thèse, nous étudions théoriquement et expérimentalement l’interaction Casimir-Polder entre un atome de césium fortement excité (atome de Rydberg) et une surface diélectrique. Notre théorie étend les études précédentes pour inclure des termes d’ordre supérieur dans l’interaction atome-surface, au-delà du terme d’interaction dipôle-dipôle étudié dans le travail de Casimir et Polder. En particulier, nous incluons des termes d’interaction quadrupole-quadrupole et dipôle-octupole avec une dépendance en distance de -C5/z5. Nous fournissions également des calculs explicites des coefficients C5 pour la plupart des atomes alcalins courants. Nous décrivons également une nouvelle expérience de réflexion sélective sondant des atomes de Rydberg de Cs (15-17D3/2 et 16-17S1/2) à des distances nanométriques d’une surface de saphir. L’expérience est réalisée dans une cellule à vapeur entièrement en saphir en utilisant une spectroscopie d’excitation par étapes qui comprend une étape de pompage à 6S1/2?6P1/2 (894nm) et une étape de sondage par réflexion sélective à 6P1/2?nS1/2 , nD3/2 avec n=15-17 (~510nm). Afin d’analyser nos spectres expérimentaux, nous étendons la théorie de la réflexion sélective au-delà de l’approximation Doppler infinie, en incluant dans notre analyse la distribution Maxwell-Boltzmann des vitesses atomiques. L’ajustement de nos spectres expérimentaux avec nos modèles théoriques nous permet d’extraire le coefficient de van der Waals C3 pour les états excités du césium sondés. Les résultats expérimentaux dépassent nos prédictions théoriques (d’un facteur d’environ 1,5 à 2, selon l’état sondé). Enfin, nous décrivons une nouvelle expérience en cellule mince qui vise à éclaircir le désaccord signalé entre la théorie et l’expérience pour le coefficient C3 et à fournir une première mesure expérimentale du coefficient C5 (étude expérimentale des interactions d’ordre supérieur).
In the extreme near-field, when the spatial extension of the atomic wavefunction is no longer negligible compared to the atom-surface distance, the dipole approximation is no longer sufficient to describe Casimir-Polder interactions. Here we calculate the higher-order, quadrupole and octupole, contributions to Casimir-Polder energy shifts of Rydberg atoms close to a dielectric surface. We subsequently investigate the effects of these higher-order terms in thin-cell and selective reflection spectroscopy. Beyond its fundamental interest, this new regime of extremely small atom surface separations is relevant for quantum technology applications with Rydberg or surface-bound atoms interfacing with photonic platforms.
In the extreme near field, when the spatial extension of the atomic wavefunction is no longer negligible compared to the atom-surface distance, the dipole approximation is no longer sufficient to describe Casimir-Polder interactions. Here we calculate the higher-order, quadrupole and octupole, contributions to Casimir-Polder energy shifts of Rydberg atoms close to a dielectric surface. We subsequently investigate the effects of these higher-order terms in thin-cell and selective reflection spectroscopy. Beyond its fundamental interest, this regime of extremely small atom surface separations is relevant for quantum technology applications with Rydberg or surface-bound atoms interfacing with photonic platforms. Published by the American Physical Society 2024