Synchronization and bistability of qubit coupled to a driven dissipative oscillator

TL;DR

This paper investigates how a qubit coupled to a driven dissipative oscillator exhibits synchronization and bistability, leading to metastable states and spectral changes, with implications for quantum lasing phenomena.

Contribution

It numerically demonstrates the emergence of synchronization and bistability in a qubit-oscillator system, revealing new dynamical regimes and spectral features.

Findings

Qubit synchronization occurs above a critical coupling strength.

Metastable states with long lifetimes are observed.

Spectral lines indicate single artificial-atom lasing.

Abstract

We study numerically the behavior of qubit coupled to a quantum dissipative driven oscillator (resonator). Above a critical coupling strength the qubit rotations become synchronized with the oscillator phase. In the synchronized regime, at certain parameters, the qubit exhibits tunneling between two orientations with a macroscopic change of number of photons in the resonator. The life times in these metastable states can be enormously large. The synchronization leads to a drastic change of qubit radiation spectrum with appearance of narrow lines corresponding to recently observed single artificial-atom lasing [O. Astafiev {\it et al.} Nature {\bf 449}, 588 (2007)].