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Kinetics of Superconducting Quantum Circuit


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.