Postdoctoral Research Seminars
1) Speaker: Michael Foss-Feig
Title:Entanglement in long-range interacting systems.
Abstract: It is well known that infinite-range interactions can facilitate the generation of massively entangled states with applications in quantum information and quantum metrology. From a theoretical standpoint, such infinite-range interactions are convenient to assume because they greatly simplify the description of dynamics, but in physical systems "infinite-range" is clearly an approximation. In this talk, I will describe what happens to a number of experimentally relevant systems when interactions are long-ranged but not infinite-ranged.
2) Speaker: Fred Jendrzejewski
Title: From compressed Bose-Einstein condensates to spirals-New Experiments with superfluid atom circuits
Abstract: Bose-Einstein condensates in ring geometries are essential ingredients to the ongoing effort at JQI of building increasingly complex superfluid circuits. Such circuits have previously allowed for the observation of persistent currents and hysteresis. Here we report on two new experiments that increase our abilities further. First, we report the direct observation of resistive flow through a weak link in a weakly interacting atomic Bose- Einstein condensate. We use two weak links to separate our ring-shaped superfluid circuit into two distinct regions, a source and a drain. At a critical value of the weak link velocity, we observe a transition from superfluid flow to superfluid plus resistive flow. Second, we demonstrate a new technique to directly observe the current-phase relationship through such weak links. By interfering our ring with a phase reference (formed as a disc), we demonstrate that we can measure the phase of the BEC around the ring and the average current.