The achievable fidelity of many nanoelectronic devices based on superconducting aluminum is limited by either the density of residual nonequilibrium quasiparticles nqp or the density of quasiparticle states in the gap, characterized by Dynes parameter γ. We infer upper bounds nqp<0.033μm−3 and γ<1.6×10−7 from transport measurements performed on Al/Cu/Al single-electron transistors, improving previous results by an order of magnitude. Owing to efficient microwave shielding and quasiparticle relaxation, a typical number of quasiparticles in the superconducting leads is zero.
|Number of pages||4|
|Journal||Physical Review B|
|Publication status||Published - 20 Jan 2012|
|MoE publication type||A1 Journal article-refereed|
- quasiparticle density
- single-electron transistor