RUI: Quantum Turbulence in Atomtronic Systems

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An "atom circuit" is a thin sheet of atomic gas that has been confined to two-dimensions by squeezing it with laser light and cooling it to nearly the absolute zero of temperature. The low temperature of such confined gases enhances the display of the wave-like quantum mechanical nature of the constituent atoms so that they form a state called a Bose-Einstein condensate (BEC). A horizontal thin sheet of gas in the BEC state can be molded by the confining laser light into arbitrary closed-loop shapes analogous to closed electric circuits. The gas can then be stirred by lasers so that it flows around the closed loop like the electrons in an electric circuit except that the particles are neutral atoms. "Atomtronics" is accordingly an analogue of electronics in which entire atoms flow through a circuit. Atomtronic systems are of interest because they could potentially be used as extremely sensitive quantum sensors of rotations, of magnetic fields, and of gravitational fields. This research program will study how the quantum turbulence that often appears when such gases are stirred can be harnessed to enhance the operation of these quantum sensor devices. Methods for readout of the important characteristics of these circuits (such as analogs of ammeters and voltmeters in electric circuits) will be developed. This work, performed with undergraduate students at an RUI institution, is conducted in close collaboration with experimental researchers at JQI/NIST.The collaboration will study the behavior of ultracold samples of atomic gases strongly confined in a horizontal plane and subjected to arbitrary space-dependent and time-dependent potentials produced by laser light. The research will take advantage of recent experimental breakthroughs in the optical manipulation of ultracold gases in designing new atom circuit potentials. In this work a variety of different atom-circuit designs will be investigated. Each atom circuit to be studied will be assumed to be completely filled by the atoms condensed into a BEC. Methods of producing condensate flow, especially smooth flow, will be studied. The operation of each atom circuit will be simulated both at zero and non-zero temperature. The flow present in atom circuits often involves the appearance of numerous topological excitations such as vortices (i.e., miniature tornadoes in the gas) and solitons (solitary waves that move without degrading) and thus exhibits "quantum turbulence". One focus of this research will be to detect the presence of all such excitations and then follow and analyze their behavior. These studies will enable the development of simple models of vortex and solitonic behavior in the atomtronic systems. Such models will be useful in designing optimally performing atom circuits for applications. This research program will enable at least two undergraduate physics majors to gain state-of-the-art research experience in the area of ultracold atom theory. The project will enhance the infrastructure for research and education by enhancing an established collaboration among an undergraduate institution (GA Southern), a national laboratory (NIST), and a major research university (University of Maryland). Results of this research will be broadly disseminated to enhance scientific and technological understanding by developing virtual reality (VR) videos that describe the physics of BECs at a level that is accessible to the lay public. These VR videos will be suitable for display on VR headsets such as the Oculus Rift and Google Cardboard. Finally, an understanding of the role of quantum turbulence in atom-circuits will enable the design of a new generation of practical devices that will find applications in metrology and navigation. This knowledge will also add to the understanding of the fundamental properties of quantum matter.