Quasiparticle dynamics and decoherence in superconducting qubits

Quasiparticle dynamics and decoherence in superconducting qubits
Chen Wang, Department of Applied Physics, Yale University
Date and time: Mon, Feb 23, 2015 - 12:15pm
Location: ILC N101
Category: Condensed Matter Seminar
Abstract:
Superconducting quantum circuits have attracted growing interest in recent years as a promising candidate for fault-tolerant quantum information processing, powered by dramatic improvements of their coherence times. Further advancement in coherence requires understanding of all the non-equilibrium processes in play in superconducting aluminum films in new regimes. In this talk I will present measurements of the dynamics of a very low density of quasiparticle excitations in aluminum at 20 mK using a superconducting qubit as a sensitive probe. We directly demonstrate the power-law decay characteristics of the canonical quasiparticle recombination process, and show quantized changes of quasiparticle trapping rate due to individual vortices. We introduce and measure an intrinsic “trapping power” of a vortex, P = 0.067 cm2/s, that conveniently describes the vortex-quasiparticle interaction. A small nonequilibrium quasiparticle generation rate corresponding to an energy in-flux of 2x10-20W/μm2 is measured in our device, whose origin remains to be determined.