Quantum phase slips in a resonant Josephson junction

TL;DR

This paper studies how resonant tunneling affects quantum phase slips in Josephson junctions, revealing a transition from 2π to 4π phase slips near resonance, with implications for superconducting qubits.

Contribution

It demonstrates how Landau-Zener transitions modify quantum tunneling in Josephson junctions, leading to dominant 4π phase slips near resonance.

Findings

Suppression of 2π phase slips near resonance

Emergence of 4π phase slips as dominant process

Residual charge dispersion persists at perfect transparency

Abstract

We investigate the consequences of resonant tunneling of Cooper pairs on the quantum phase slips occurring in a Josephson junction. The amplitude for quantum tunneling under the Josephson potential barrier is modified by the Landau-Zener amplitude of adiabatic passage through an Andreev level crossing, resulting in the suppression of $2\pi$ phase slips. As a consequence, close to resonance, $4\pi$ phase slips become the dominant tunneling process. We illustrate this crossover by determining the energy spectrum of a transmon circuit, showing that a residual charge dispersion persists even at perfect transparency.