Phase Transitions in Trajectories of a Superconducting Single-Electron Transistor Coupled to a Resonator

TL;DR

This paper applies a large-deviation approach to analyze dynamical phase transitions in a superconducting single-electron transistor coupled to a resonator, revealing rich fluctuation behavior and phase bistabilities even at low activity levels.

Contribution

It introduces a quantum-jump trajectory analysis of a superconducting SET-resonator system, uncovering phase transitions and bistability phenomena in the dynamical activity.

Findings

Sharp dynamical activity transitions linked to bistability in the resonator

Rich fluctuation behavior observed even with low mean activity

Trajectory analysis shows similarity between quasiparticle and resonator dynamics for fast resonators

Abstract

Recent progress in the study of dynamical phase transitions has been made with a large-deviation approach to study trajectories of stochastic jumps using a thermodynamic formalism. We study this method applied to an open quantum system consisting of a superconducting single-electron transistor, near the Josephson quasiparticle resonance, coupled to a resonator. We find that the dynamical behavior shown in rare trajectories can be rich even when the mean dynamical activity is small and thus the formalism gives insights into the form of fluctuations. The structure of the dynamical phase diagram found from the quantum-jump trajectories of the resonator is studied and we see that sharp transitions in the dynamical activity may be related to the appearance and disappearance of bistabilities in the state of the resonator as system parameters are changed. We also demonstrate that for a fast resonator, the trajectories of quasiparticles are similar to the resonator trajectories.