Seminar Schedule

Ultracold quantum gases are excellent platforms for quantum simulation and sensing. So far these gases have been produced using time-sequential cooling stages and after creation they unfortunately decay through unavoidable loss processes. This limits what can be done with them. For example it becomes impossible to extract a continuous-wave atom laser, which has promising applications for precision measurement through atom interferometry [1]. In the first part of this talk I will present how we create continuous-wave BECs, BECs that persist in a steady-state for as long as we desire. Atom loss is compensated by feeding fresh atoms from a continuously replenished thermal source into the BEC by Bose-stimulated gain [2]. The only step missing to create the long-sought continuous-wave atom laser is the addition of a coherent atom outcoupling mechanism. In addition this BEC may give us access to interesting driven-dissipative quantum phenomena over unprecedented timescales. The techniques we developed to create the continuous source of thermal atoms are also nicely suited to tackle another challenge: the creation of a continuously operating superradiant clock [3]. These clocks promise to become more rugged or more short-term stable than traditional optical clocks, thereby opening new application areas. In the second part of my talk I will present how we are developing two types of superradiant clocks within the European Quantum Flagship consortium iqClock. The first operates on a kHz-wide transition of Sr [4] and the other on the mHz-narrow Sr clock transition

It is thought that the rapid expansion of the early universe resulted in the spontaneous production of cosmological particles. The latter evolved into the patterns in the cosmic microwave background visible today. The analogue of cosmological particle creation in a quantum fluid could provide insight, but an observation was not achieved previously. This talk presents our observation of analogue cosmological particle creation in a 3-dimensional quantum fluid of light. The process is seen to be spontaneous, and in close quantitative agreement with the quantum-field theoretical prediction. We find that the long-wavelength particles provide a window to early times, and we apply this principle to the cosmic microwave background. This work introduces a new quantum fluid, as cold as an atomic Bose-Einstein condensate.