title: Cooling and Autonomous Feedback in a Bose-Hubbard Chain with Attractive Interactions.
abstract: We engineer a quantum bath that enables entropy and energy exchange with a one-dimensional Bose-Hubbard lattice with attractive on-site interactions. We implement this in an array of three superconducting transmon qubits coupled to a single cavity mode; the transmons represent lattice sites and their excitation quanta embody bosonic particles. Our cooling protocol preserves the particle number-realizing a canonical ensemble-and also affords the efficient preparation of dark states which, due to symmetry, cannot be prepared via coherent drives on the cavity. Furthermore, by applying continuous microwave radiation, we also realize autonomous feedback to indefinitely stabilize particular eigenstates of the array.
authors.affiliation: Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: S
authors.initials: S
authors.lastname: Hacohen-Gourgy
authors.affiliation: Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: V V
authors.initials: VV
authors.lastname: Ramasesh
authors.affiliation: Departments of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: C
authors.initials: C
authors.lastname: De Grandi
authors.affiliation: Quantum Nanoelectronics Laboratory, Department of Physics, University of California, Berkeley, California 94720, USA.
authors.forename: I
authors.initials: I
authors.lastname: Siddiqi
authors.affiliation: Departments of Physics and Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: S M
authors.initials: SM
authors.lastname: Girvin