Engineering Double-Well Potentials with Variable-Width Annular Josephson Tunnel Junctions

Abstract

Long Josephson tunnel junction are non-linear transmission lines that allow propagation of current vortices (fluxons) and electromagnetic waves and are used in various applications within superconductive electronics. Recently, the Josephson vortex has been proposed as a new superconducting qubit. We describe a simple method to create a double-well potential for an individual fluxon trapped in a long elliptic annular Josephson tunnel junction characterized by an intrinsic non-uniform width. The distance between the potential wells and the height of the inter-well potential barrier are controlled by the strength of an in-plane magnetic field. The manipulation of the vortex states can be achieved by applying a proper current ramp across the junction. The read-out of the state is accomplished by measuring the vortex depinning current in a small magnetic field. An accurate one-dimensional sine-Gordon model for this strongly non-linear system is presented, from which we calculate the position-dependent fluxon rest-mass, its Hamiltonian density and the corresponding trajectories in the phase space. We examine the dependence of the potential properties on the annulus eccentricity and its electrical parameters and address the requirements for observing quantum-mechanical effects, as discrete energy levels and tunneling, in this two-state system.

18 pages, 9 figures

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• Kink-inhomogeneity interaction in the sine-Gordon model
• Flux Flow Effects in Annular Josephson Tunnel Junctions
• Confocal Annular Josephson Tunnel Junctions with Large Eccentricity
• An effective description of the impact of inhomogeneities on the movement of the kink front in 2+1 dimensions
• Field Cooled Annular Josephson Tunnel Junctions
• Kink movement on a periodic background
• Modelling assisted tunneling on the Bloch sphere using the Quantum Composer