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Résumé |
Most Josephson junctions used in superconducting circuits are tunnel junctions,
characterized by a thin insulating barrier. In this talk, I will present two
alternative approaches for making non-tunnel Josephson junctions, developed at
the QCMX lab at École Polytechnique. These innovative designs not only deepen
our understanding of the underlying microscopic phenomena but also hold
significant promise for advancing quantum information technologies.
The first type of junctions involves Superconductor / Carbon Nanotube /
Superconductor structures. We have pioneered a novel technique [1] for
integrating ultra-clean carbon nanotubes into superconducting circuits.
Transport measurements in these junctions reveal hundreds of well-defined
Coulomb diamonds, and I will demonstrate the coherent manipulation of a gate-
tunable qubit based on this architecture.
The second approach focuses on pinhole junctions, where transport is dominated
by a few conduction channels with near-unity transmission. This is evidenced by
the observation of Multiple Andreev Reflections in the current-voltage
characteristics. Harnessing these high-transmission channels could enable the
implementation of the highly sought-after cos(2φ) qubit [2].
[1] S. Annabi, et al., arXiV 2405.19192 (accepted in Phys. Rev. App.)
[2] W. Smith, et al., npj Quantum Information 6 (2020)
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