Freiburg 2019 – scientific programme

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FM: Fall Meeting

FM 17: Quantum Computation: Simulation I

FM 17.7: Talk

Monday, September 23, 2019, 18:00–18:15, 1010

Shell structure and deterministic preparation of microscopic two dimensional systems — •Luca Bayha, Marvin Holten, Ralf Klemt, Keerthan Subramanian, Philipp Preiß, and Selim Jochim — Physics Institute, Heidelberg University, Germany

The interplay between strong paring and shell structures arising from finite numbers creates very rich physics. For example the state of fermions in the BEC-BCS crossover is determined by the competition between pairing and single particle gaps. Here I will present our progress on quantum simulation of such mesoscopic fermionic systems using ultracold atoms. We recently archived the deterministic preparation of up to 12 fermions in the ground state of a two dimensional trap and observed the shell structure of the sample. We use a Feshbach resonance to tune interactions and study the finite size BEC-BCS crossover. For filled shells there is a minimal required attraction for pairing to overcome the single particle gap. Thus the ground state of the BEC-BCS crossover undergoes a quantum phase transition from normal to superfluid. This phase transition is accompanied by a Higgs mode. Remarkably, we found a precursor of this mode in a microscopic system consisting of only 6 fermions. Doing spectroscopy we observed mode softening close the critical binding energy of the many body system. This mode consists mainly of pair excitations, which we show by measuring the full counting statistics. In the future we plan to investigate the system using momentum and spin resolved single particle imaging. This will give insight into the pairing mechanisms, entanglement and correlations of the strongly interacting Fermi gas.