Confocal Annular Josephson Tunnel Junctions with Large Eccentricity

Roberto Monaco*, Jesper Mygind, Lyudmila V. Filippenko

*Corresponding author for this work

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Confocal annular Josephson tunnel junctions (CAJTJs), which are the natural generalization of the circular annular Josephson tunnel junctions, have a rich nonlinear phenomenology due to the intrinsic non-uniformity of their planar tunnel barrier delimited by two closely spaced confocal ellipses. In the presence of a uniform magnetic field in the barrier plane, the periodically changing width of the elliptical annulus generates a asymmetric double-well for a Josephson vortex trapped in a long and narrow CAJTJ. The preparation and readout of the vortex pinned in one of the two potential minima, which are important for the possible realization of a vortex qubit, have been numerically and experimentally investigated for CAJTJs with the moderate aspect ratio 2:1. In this work, we focus on the impact of the annulus eccentricity on the properties of the vortex potential profile and study the depinning mechanism of a fluxon in more eccentric samples with aspect ratio 4:1. We also discuss the effects of the temperature-dependent losses as well as the influence of the current and magnetic noise.
Original languageEnglish
JournalJournal of Low Temperature Physics
Issue number5-6
Pages (from-to)315-329
Number of pages15
Publication statusPublished - 2018


  • Double-well potential
  • Josephson devices
  • Quantum computation
  • Solitons


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