Quasiparticles in superconducting qubits with asymmetric junctions
- URL: http://arxiv.org/abs/2205.06056v2
- Date: Sun, 27 Nov 2022 07:55:30 GMT
- Title: Quasiparticles in superconducting qubits with asymmetric junctions
- Authors: Giampiero Marchegiani, Luigi Amico, Gianluigi Catelani
- Abstract summary: We consider quasiparticle effects in superconducting qubits to account for asymmetry in the gap on the two sides of a Josephson junction.
We find that different regimes can be encountered in which the quasiparticles have either similar densities in the two junction leads, or are largely confined to the lower-gap lead.
- Score: 0.0
- License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
- Abstract: Designing the spatial profile of the superconducting gap -- gap engineering
-- has long been recognized as an effective way of controlling quasiparticles
in superconducting devices. In aluminum films, their thickness modulates the
gap; therefore, standard fabrication of Al/AlOx/Al Josephson junctions, which
relies on overlapping a thicker film on top of a thinner one, always results in
gap-engineered devices. Here we reconsider quasiparticle effects in
superconducting qubits to explicitly account for the unavoidable asymmetry in
the gap on the two sides of a Josephson junction. We find that different
regimes can be encountered in which the quasiparticles have either similar
densities in the two junction leads, or are largely confined to the lower-gap
lead. Qualitatively, for similar densities the qubit's excited state population
is lower but its relaxation rate higher than when the quasiparticles are
confined; therefore, there is a potential trade-off between two desirable
properties in a qubit.
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