@phdthesis{oai:oist.repo.nii.ac.jp:00002786,
 author = {Keller, Tim},
 month = {2022-09-16, 2022-09-16},
 note = {In this thesis, I present two studies on controlling the state and properties of both single-species and composite quantum gases by tuning the various interaction strengths. In the first work, I derive a shortcut to adiabaticity (STA) for tuning a Feshbach resonance in repulsively interacting Bose-Einstein condensates (BECs) in the ThomasFermi regime. This shortcut mimics an adiabatic evolution and allows one to compress and expand a BEC without friction within an almost arbitrarily short time interval. I then use this technique to show how it can boost the performance of the so-called Feshbach quantum engine and also determine its limits and the instabilities it can lead to. The first part is complemented by a study demonstrating the general ineffectiveness of STAs as a tool to increase the attainable precision in critical quantum metrology at the example of two critical toy models. In the second part, I show that a strongly correlated one-dimensional quantum gas in the Tonks-Girardeau (TG) limit that is immersed into a BEC can undergo a transition to a crystal-like insulator state without any externally imposed lattice potential. I develop a model that accurately describes the system in the pinned insulator state, even if the TG gas has a finite temperature. Additionally, I study the superfluid state that can persist in the gas for finite interactions away from the TG limit and uncover the full phase diagram of the system.},
 school = {Okinawa Institute of Science and Technology Graduate University},
 title = {相互作用する量子気体における超流動状態および絶縁状態の制御},
 year = {}
}