Running-phase state in a Josephson washboard potential

TL;DR

This paper analyzes the phase dynamics of underdamped Josephson junctions during switching experiments, revealing how wavepacket propagation causes a linear increase in average voltage over time, relevant for quantum tunneling and qubit read-out.

Contribution

It provides a detailed calculation of the macroscopic wavepacket shape and its impact on voltage evolution after switching events in Josephson junctions.

Findings

Wavepacket shape influences voltage increase

Linear voltage growth observed after switching

Macroscopic quantum tunneling evidence reinforced

Abstract

We investigate the dynamics of the phase variable of an ideal underdamped Josephson junction in switching current experiments. These experiments have provided the first evidence for macroscopic quantum tunneling in large Josephson junctions and are currently used for state read-out of superconducting qubits. We calculate the shape of the resulting macroscopic wavepacket and find that the propagation of the wavepacket long enough after a switching event leads to an average voltage increasing linearly with time.