Quantum dissociation of a vortex-antivortex pair in a long Josephson junction

TL;DR

This paper combines theoretical analysis and experimental observations to study the quantum behavior of vortex-antivortex pairs in long Josephson junctions, revealing magnetic field effects and a transition to quantum tunneling at low temperatures.

Contribution

It provides the first detailed analysis of quantum dissociation of VAV pairs in Josephson junctions, including experimental validation of quantum tunneling effects.

Findings

Observation of increased switching current distribution width with magnetic field

Identification of a crossover to quantum tunneling at around 100 mK

Prediction of magnetic field dependence of energy levels

Abstract

We report a theoretical analysis and experimental observation of the quantum dynamics of a single vortex-antivortex (VAV) pair confined in a long narrow annular Josephson junction. The switching of the junction from the superconducting state to the resistive state occurs via the dissociation of a pinned VAV pair. The pinning potential is controlled by external magnetic field $H$ and dc bias current $I$. We predict a specific magnetic field dependence of the oscillatory energy levels of the pinned VAV state and the crossover to a {\it macroscopic quantum tunneling} mechanism of VAV dissociation at low temperatures. Our analysis explains the experimentally observed {\it increase} of the width of the switching current distribution $P(I)$ with $H$ and the crossover to the quantum regime at the temperature of about 100 mK.