Quantum State Engineering with Bose-Einstein Condensates: Dressed-State and Hydrodynamic Approaches

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This project employs ultracold atomic gases to model complex quantum mechanical phenomena. Using laser cooling and related techniques, a cloud of atoms is cooled down to temperatures near absolute zero. Under appropriate conditions the atoms coalesce into a Bose-Einstein condensate, a macroscopic matter wave displaying quantum mechanical behavior. The large size of these objects, which can extend over hundreds of microns, implies that they are readily observable using custom imaging optics, and a rich toolset based on atomic physics is available for their manipulation. This, together with their quantum mechanical nature, makes them an ideal platform to study complex quantum mechanical phenomena. With the recent and ongoing development of novel experimental tools and theoretical approaches, such quantum analog modeling has become a major thrust of research in Atomic, Molecular and Optical (AMO) physics. Ultracold atom platforms can be applied to study phenomena from condensed matter physics, nonlinear science, hydrodynamics, quantum optics, and more, demonstrating their importance as highly versatile testbeds in modern physics. The experiments conducted in this project investigate several approaches to probe the emergence of periodic structures with crystal-like properties from the macroscopic matter wave of a Bose-Einstein condensate. The dynamical properties of such crystalline structures pose many theoretical challenges, and the experiments provide essential benchmark data for the development of a theoretical understanding. Going beyond the realm of ultracold atoms, the insight gained through this line of research is of high relevance for condensed matter physics and nonlinear science as well. The experiments are conducted with complex setups that utilize a large range of modern experimental techniques, including lasers and optics, ultrahigh vacuum technology, automation programming, and advanced electronics. This makes them ideal platforms to train students in a multitude of areas relevant for modern quantum technologies which use quantum mechanical effects in sensor applications e.g. to detect magnetic, electric or gravitational fields, for fundamentally secure communication, or to establish new paradigms for efficient computing. This research program advocates the use of ultracold atomic gases as a highly flexible platform for the study of quantum phases and dynamics. Along the lines of quantum analog simulation, several innovative approaches to investigate emerging band structures and associated phenomena in dilute-gas Bose-Einstein condensates (BECs) are employed. The starting point is a BEC in which spin and motional degrees of freedom are coupled by a set of Raman laser beams. This spin-orbit coupling is then supplemented with a radiofrequency dressing or microwave dressing to generate effective lattice structures with unusual properties. In the first case, an effective Zeeman lattice emerges even though neither the spin-orbit coupling nor the radiofrequency alone produce a periodic band structure. The second case leads to a new method to generate a supersolid-like state with large spatial periodicity, overcoming the limitations of previous approaches. As a third, complementary approach coming from a quantum hydrodynamics perspective, the experimental realization of densely packed interacting soliton trains provides a very different and unexplored access to the study of crystalline properties that arise in a superfluid system without imposing a periodic external potential. The quantum analog simulation of condensed matter, hydrodynamic or nonlinear phenomena using the versatile toolbox of atomic physics is a highly active area in quantum gas research, and the experiments provide important benchmark data motivating the concurrent development of theoretical approaches.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.