Summary form only given. Experimental studies of the atom-surface or surface-surface interactions provide a physical insight on the interaction of quantum bodies with the fluctuating vacuum. They can be of great practical interest in the ever expanding field of nanotechnologies. In particular the dependence of the Casimir and Casimir-Polder interaction on the thermal fluctuations is a fundamental effect that could in the future provide a useful knob for tuning these interactions. Temperature effects are usually very small and have so far been observed on a BEC placed 6-10 μm away from a fused-silica substrate due to an out of thermal equilibrium enhancement. Here we report on spectroscopic selective reflection measurements of the interaction between a Cs (7D3/2) atom and a sapphire surface. A virtual coupling between a surface resonance of sapphire at 12.1 μm and the Cs 7D3/2Æ5F5/2 transition at 10.8 μm almost eliminates the resonant contribution for this dipole transition. Reaching the temperatures required to observe an effect is extremely challenging. For this reason our experiment is performed in an all-sapphire vapour cell with super polished windows with an annealing post-treatment. The interaction is probed up to unusually high temperatures reaching more than 1000 K. Experimental measurements show C3coefficient as a function of temperature compared to a full QED calculation. Each point is deduced by fitting reflection spectra to a theoretical model and is averaged for different vapour densities and different spots on the window. Statistical and systematic uncertainties have been reduced compared to our previous experiments performed on a different all-sapphire cell with windows of uncertain surface quality. The chemical stability of sapphire under these extreme conditions seems to be a key factor for this experimental achievement. Previous measurements between Cs (8P3/2) and a CaF2surface in a specially designed cell were unsuccessful due to chemical deterioration of the surface. This experiment is the first to provide a sensitive measurement of temperature effects on the atom-surface interaction in thermal equilibrium and highlights the QED nature of van der Waals regime.
Summary form only given. Experimental studies of the atom-surface or surface-surface interactions provide a physical insight on the interaction of quantum bodies with the fluctuating vacuum. They can be of great practical interest in the ever expanding field of nanotechnologies. In particular the dependence of the Casimir and Casimir-Polder interaction on the thermal fluctuations is a fundamental effect that could in the future provide a useful knob for tuning these interactions. Temperature effects are usually very small and have so far been observed on a BEC placed 6-10 μm away from a fused-silica substrate due to an out of thermal equilibrium enhancement. Here we report on spectroscopic selective reflection measurements of the interaction between a Cs (7D3/2) atom and a sapphire surface. A virtual coupling between a surface resonance of sapphire at 12.1 μm and the Cs 7D3/2Æ5F5/2 transition at 10.8 μm almost eliminates the resonant contribution for this dipole transition. Reaching the temperatures required to observe an effect is extremely challenging. For this reason our experiment is performed in an all-sapphire vapour cell with super polished windows with an annealing post-treatment. The interaction is probed up to unusually high temperatures reaching more than 1000 K. Experimental measurements show C3coefficient as a function of temperature compared to a full QED calculation. Each point is deduced by fitting reflection spectra to a theoretical model and is averaged for different vapour densities and different spots on the window. Statistical and systematic uncertainties have been reduced compared to our previous experiments performed on a different all-sapphire cell with windows of uncertain surface quality. The chemical stability of sapphire under these extreme conditions seems to be a key factor for this experimental achievement. Previous measurements between Cs (8P3/2) and a CaF2surface in a specially designed cell were unsuccessful due to chemical deterioration of the surface. This experiment is the first to provide a sensitive measurement of temperature effects on the atom-surface interaction in thermal equilibrium and highlights the QED nature of van der Waals regime.
We report on the analysis of FM selective reflection experiments on the 6S1/2->8P3/2 transition of Cs at 388 nm, and on the measurement of the surface van der Waals interaction exerted by a sapphire interface on Cs(8P3/2). Various improvements in the systematic fitting of the experiments have permitted to supersede the major difficulty of a severe overlap of the hyperfine components, originating on the one hand in a relatively small natural structure, and on the other hand on a large pressure broadening imposed by the high atomic density needed for the observation of selective reflection on a weak transition. The strength of the van der Waals surface interaction is evaluated to be 73±10 kHz.µm3. An evaluation of the pressure shift of the transition is also provided as a by-product of the measurement. We finally discuss the significance of an apparent disagreement between the experimental measurement of the surface interaction, and the theoretical value calculated for an electromagnetic vacuum at a null temperature. The possible influence of the thermal excitation of the surface is evoked, because, the dominant contributions to the vW interaction for Cs(8P3/2) lie in the far infrared range.
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 (C-P) interaction between an atom and a surface, described as early as 1948, but observed much later on, is now a topic of broad interest, as connected to fundamental problems of quantum fluctuations, with the atomic energy levels renormalized by the wall-dependent vacuum fluctuations. Dependence of the C-P interaction with the equilibrium temperature is predicted, but had not been observed until now. However, more pronounced effects were predicted in an out-of-equilibrium situation, and were remarkably observed on a Rb BEC, at 6-10 μm from the wall, with the vacuum temperature (~ 300K) strongly differing from the surface temperature (~ 1000 K).
We report on the analysis of FM selective reflection experiments on the 6S 1/2 → 8P 3/2 transition of Cs at 388 nm, and on the measurement of the surface van der Waals interaction exerted by a sapphire interface on Cs(8P 3/2). Various improvements in the systematic fitting of the experiments have permitted us to supersede the major difficulty of a severe overlap of the hyperfine components, originating, on the one hand, in a relatively small natural structure, and, on the other hand, on a large pressure broadening imposed by the high atomic density needed for the observation of selective reflection on a weak transition. The strength of the van der Waals surface interaction is evaluated to be 73 ± 10 kHz µm3. An evaluation of the pressure shift of the transition is also provided as a by-product of the measurement. Finally, we discuss the significance of an apparent disagreement between the experimental measurement of the surface interaction, and the theoretical value calculated for an electromagnetic vacuum at a null temperature. The possible influence of the thermal excitation of the surface is evoked, because the dominant contributions to the van der Waals interaction for Cs(8P 3/2) lie in the far-infrared range.
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).
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.