Experimental characterization of blackbody induced transitions in high-lying Rydberg atoms

With increasing complexity of the quantum description of nature, the possibility to simulate physical systems with other controllable quantum systems is becoming more and more interesting. To physically implement such a quantum simulator, highly excited atomic states, known as Rydberg states, have been proposed for their extreme properties such as strong controllable interactions and long lifetime. In this thesis, experimental studies of the lifetime of very high-lying Rubidium Rydberg states for various angular momenta are reported. In my thesis, the experimental set-up needed to create ultracold atomic samples and to excite them to Rydberg states is described in detail. Furthermore, the experimental technique developed in our laboratory, based on state-selective de-excitation, which allows us to perform lifetime measurements of high-lying Rydberg states, is explained. Numerical simulations of a Rydberg state interacting with blackbody radiation were performed to derive theoretical predictions with which to compare our data. Our experimental results for S states are in good agreement with theoretical predictions, except for two small ranges of principal quantum numbers. To experimentally study these deviations, we modified the excitation and de-excitation techniques in order to perform the same lifetime measurements for P states. From the comparison of the results for S and P states, we found a correlation between lifetime values lower than expected and transition frequencies to neighbouring levels. A possible explanation of such a disagreement between theoretical predictions and experimental data is given in terms of deviation from Planck’s formula due to geometrical effects. In conclusion, we demonstrated the possibility to accurately measure the lifetime of very high-lying Rydberg states for different angular momenta. We highlight the necessity of precise analysis of the geometry of the apparatus near the atoms, in order to achieve a simple theoretical description of the lifetime of Rydberg atoms