Abstract:
Superconducting circuits exhibit quantum properties on a
macroscopic scale, and are natural candidates for solid state quantum computing. Their low-energy physics can be described in
terms of the phase of the order parameter, a single collective
degree of freedom associated with billions of coherently paired
electrons. In practice, however, on top of the superfluid
condensate there are single-particle excitations (quasiparticles) with a continuum energy spectrum; the quasiparticles are coupled
to the phase degree of freedom. The presence of the quasiparticles
in the system sets serious constraints on the performance of
superconducting charge qubits.
In my talk, I will discuss the kinetics of superconducting quantum circuits in the presence of quasiparticles. First, I will consider
the kinetics of quasiparticle trapping in a small superconducting
island and talk about the statistics of quasiparticle capture and
emission processes. Second, I will discuss the quasiparticle
contribution to the energy and phase relaxation of a
superconducting charge qubit.