title: Ultrafast many-body interferometry of impurities coupled to a Fermi sea.
abstract: The fastest possible collective response of a quantum many-body system is related to its excitations at the highest possible energy. In condensed matter systems, the time scale for such "ultrafast" processes is typically set by the Fermi energy. Taking advantage of fast and precise control of interactions between ultracold atoms, we observed nonequilibrium dynamics of impurities coupled to an atomic Fermi sea. Our interferometric measurements track the nonperturbative quantum evolution of a fermionic many-body system, revealing in real time the formation dynamics of quasi-particles and the quantum interference between attractive and repulsive states throughout the full depth of the Fermi sea. Ultrafast time-domain methods applied to strongly interacting quantum gases enable the study of the dynamics of quantum matter under extreme nonequilibrium conditions.
authors.affiliation: Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Marko
authors.initials: M
authors.lastname: Cetina
authors.affiliation: Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Michael
authors.initials: M
authors.lastname: Jag
authors.affiliation: Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Rianne S
authors.initials: RS
authors.lastname: Lous
authors.affiliation: Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Isabella
authors.initials: I
authors.lastname: Fritsche
authors.affiliation: Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria.|Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, 1098 XH Amsterdam, Netherlands.
authors.forename: Jook T M
authors.initials: JT
authors.lastname: Walraven
authors.affiliation: Institut für Quantenoptik und Quanteninformation, Österreichische Akademie der Wissenschaften, 6020 Innsbruck, Austria. rudolf.grimm@uibk.ac.at.|Institut für Experimentalphysik, Universität Innsbruck, 6020 Innsbruck, Austria.
authors.forename: Rudolf
authors.initials: R
authors.lastname: Grimm
authors.affiliation: School of Physics and Astronomy, Monash University, Victoria 3800, Australia.
authors.forename: Jesper
authors.initials: J
authors.lastname: Levinsen
authors.affiliation: School of Physics and Astronomy, Monash University, Victoria 3800, Australia.
authors.forename: Meera M
authors.initials: MM
authors.lastname: Parish
authors.affiliation: Institute for Theoretical Atomic, Molecular and Optical Physics (ITAMP), Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA.|Department of Physics, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Richard
authors.initials: R
authors.lastname: Schmidt
authors.affiliation: Department of Physics, Walter Schottky Institute and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Knap
authors.affiliation: Department of Physics, Harvard University, Cambridge, MA 02138, USA.
authors.forename: Eugene
authors.initials: E
authors.lastname: Demler