title: Microwave-induced cooling of a superconducting qubit.
abstract: We demonstrated microwave-induced cooling in a superconducting flux qubit. The thermal population in the first-excited state of the qubit is driven to a higher-excited state by way of a sideband transition. Subsequent relaxation into the ground state results in cooling. Effective temperatures as low as approximately 3 millikelvin are achieved for bath temperatures of 30 to 400 millikelvin, a cooling factor between 10 and 100. This demonstration provides an analog to optical cooling of trapped ions and atoms and is generalizable to other solid-state quantum systems. Active cooling of qubits, applied to quantum information science, provides a means for qubit-state preparation with improved fidelity and for suppressing decoherence in multi-qubit systems.
authors.affiliation: Massachusetts Institute of Technology (MIT) Francis Bitter Magnet Laboratory, Cambridge, MA 02139, USA. sov@mit.edu
authors.forename: Sergio O
authors.initials: SO
authors.lastname: Valenzuela
authors.forename: William D
authors.initials: WD
authors.lastname: Oliver
authors.forename: David M
authors.initials: DM
authors.lastname: Berns
authors.forename: Karl K
authors.initials: KK
authors.lastname: Berggren
authors.forename: Leonid S
authors.initials: LS
authors.lastname: Levitov
authors.forename: Terry P
authors.initials: TP
authors.lastname: Orlando