Relaxation of a qubit measured by a driven Duffing oscillator

TL;DR

This paper studies how a superconducting qubit relaxes when measured by a driven Josephson bifurcation amplifier, revealing state-dependent relaxation rates, resonant enhancements, and changes in effective temperature due to quasienergy resonances.

Contribution

It provides new insights into qubit relaxation dynamics under measurement conditions involving a driven Duffing oscillator, highlighting state-dependent effects and resonance phenomena.

Findings

Qubit relaxation rates vary with measurement state.

Resonant enhancement of relaxation occurs at specific frequencies.

Coupling to the oscillator alters the qubit's effective temperature.

Abstract

We investigate the relaxation of a superconducting qubit for the case when its detector, the Josephson bifurcation amplifier, remains latched in one of its two (meta)stable states of forced vibrations. The qubit relaxation rates are different in different states. They can display strong dependence on the qubit frequency and resonant enhancement, which is due to quasienergy resonances. Coupling to the driven oscillator changes the effective temperature of the qubit.