Excitation of a Bose-Einstein condensate: A Pedagogical Experiment on quantum states change

In this work, we have used a ⁸⁷Rb Bose-Einstein condensate to study the effects of electrical noise, embedded into the magnetic trap field, on the atomic population distribution spread over different quantum states of the confining potential. The noisy external field comes from unwanted fluctuations taking place in the electronic stabilization control circuit for the electric current flowing through the magnetic trap coils, which operate at frequencies close to that of the trapping potential. We will show that these small electric fluctuations are able to couple adjacent vibrational levels of the potential resulting in the population spread, which was initially pure, over a manifold of nearby states. This reduces the lifetime of the trapped condensate and also increase the average temperature of the system, as the population diffuses towards the upper energy levels. The results were modeled via ladder transitions, and directly compared to the experimental results, and were found to be in good agreement. We believe that this theoretical-experimental study is didactic, as it allows for the freshmen students to observe macroscopic quantum effects taking place on experimental physical systems.

Keywords
Bose-Einstein Condensate; thermalization; fluctuations and excitations in quantum many-body systems