title: Quasiparticle relaxation of superconducting qubits in the presence of flux.
abstract: Quasiparticle tunneling across a Josephson junction sets a limit for the lifetime of a superconducting qubit state. We develop a general theory of the corresponding decay rate in a qubit controlled by a magnetic flux. The flux affects quasiparticles tunneling amplitudes, thus making the decay rate flux-dependent. The theory is applicable for an arbitrary quasiparticle distribution. It provides estimates for the rates in practically important quantum circuits and also offers a new way of measuring the phase-dependent admittance of a Josephson junction.
authors.affiliation: Department of Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: G
authors.initials: G
authors.lastname: Catelani
authors.forename: J
authors.initials: J
authors.lastname: Koch
authors.forename: L
authors.initials: L
authors.lastname: Frunzio
authors.forename: R J
authors.initials: RJ
authors.lastname: Schoelkopf
authors.forename: M H
authors.initials: MH
authors.lastname: Devoret
authors.forename: L I
authors.initials: LI
authors.lastname: Glazman