2011/06/04 by G. Catelani, R. J. Schoelkopf, M. H. Devoret +1 · 1 citation
Physics and Astronomy · #cond-mat.mes-hall #cond-mat.supr-con #quant-ph
paper · pdf · doi:10.1103/physrevb.84.064517
published as Phys. Rev. B 84, 064517 (2011) · 25 pages, 6 figures
arxiv created 2011/06/04 · arxiv updated 2011/08/25
As low-loss non-linear elements, Josephson junctions are the building blocks of superconducting qubits. The interaction of the qubit degree of freedom with the quasiparticles tunneling through the junction represent an intrinsic relaxation mechanism. We develop a general theory for the qubit decay rate induced by quasiparticles, and we study its dependence on the magnetic flux used to tune the qubit properties in devices such as the phase and flux qubits, the split transmon, and the fluxonium. Our estimates for the decay rate apply to both thermal equilibrium and non-equilibrium quasiparticles. We propose measuring the rate in a split transmon to obtain information on the possible non-equilibrium quasiparticle distribution. We also derive expressions for the shift in qubit frequency in the presence of quasiparticles.