Vortex qubit based on an annular Josephson junction containing a microshort

TL;DR

This paper presents a combined theoretical and experimental study of a vortex qubit in an annular Josephson junction with a microshort, demonstrating controllable quantum states and readout techniques.

Contribution

It introduces a novel vortex qubit design using a microshort in an annular Josephson junction and provides a comprehensive model and experimental validation.

Findings

Successful classical state preparation and readout of the vortex

Tunable potential barrier via magnetic field adjustment

Agreement between theoretical model and experimental results

Abstract

We report theoretical and experimental work on the development of a vortex qubit based on a microshort in an annular Josephson junction. The microshort creates a potential barrier for the vortex, which produces a double-well potential under the application of an in-plane magnetic field; The field strength tunes the barrier height. A one-dimensional model for this system is presented, from which we calculate the vortex depinning current and attempt frequency as well as the interwell coupling. Implementation of an effective microshort is achieved via a section of insulating barrier that is locally wider in the junction plane. Using a junction with this geometry we demonstrate classical state preparation and readout. The vortex is prepared in a given potential well by sending a series of "shaker" bias current pulses through the junction. Readout is accomplished by measuring the vortex depinning current.