title: Measurement of the excited-state lifetime of a microelectronic circuit.
abstract: We demonstrate that a continuously measured microelectronic circuit, the Cooper-pair box measured by a radio-frequency single-electron transistor, approximates a quantum two-level system. We extract the Hamiltonian of the circuit through resonant spectroscopy and measure the excited-state lifetime. The lifetime is more than 10(5) times longer than the inverse transition frequency of the two-level system, even though the measurement is active. This lifetime is also comparable to an estimate of the known upper limit, set by spontaneous emission, for this circuit.
authors.affiliation: Department of Applied Physics and Physics, Yale University, New Haven, Connecticut 06511, USA. konrad.lehnert@yale.edu
authors.forename: K W
authors.initials: KW
authors.lastname: Lehnert
authors.forename: K
authors.initials: K
authors.lastname: Bladh
authors.forename: L F
authors.initials: LF
authors.lastname: Spietz
authors.forename: D
authors.initials: D
authors.lastname: Gunnarsson
authors.forename: D I
authors.initials: DI
authors.lastname: Schuster
authors.forename: P
authors.initials: P
authors.lastname: Delsing
authors.forename: R J
authors.initials: RJ
authors.lastname: Schoelkopf