Catelani, G. and Koch, J. and Frunzio, L. and Schoelkopf, R. J. and Devoret, Michel H. and Glazman, Leonid (2011) Quasiparticle relaxation of superconducting qubits in the presence of flux. Physical review letters, 106 (7): 077002. ISSN 0031-9007
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.