Resonance Fluorescence from a two-level artificial atom strongly coupled to a single-mode cavity

TL;DR

This paper reports the experimental observation of resonance fluorescence from a superconducting qubit strongly coupled to a cavity, revealing unique spectral features distinct from the Mollow triplet, and confirms theoretical predictions from 1989.

Contribution

First experimental demonstration of resonance fluorescence in a superconducting qubit-cavity system, validating long-standing theoretical predictions from 1989.

Findings

Central peak determined by atom spontaneous emission

Side peak widths governed by atom-cavity coherent interaction

Spectrum differs significantly from the Mollow triplet

Abstract

We experimentally demonstrate the resonance fluorescence of a two-level artificial atom strongly coupled to a single-mode cavity field. The effect was theoretically predicted thirty years ago by Savage [Phys. Rev. Lett. 63, 1376 (1989)]. The system consists of a superconducting qubit circuit and a one-dimensional transmission line resonator. In addition, a one-dimensional transmission line strongly coupled to the atom serves as an open space. The effect takes place, when a microwave field is applied to the cavity, which in turn is resonantly coupled to the atom. The fluorescence spectrum is measured via the emission into the transmission line. We find that the central peak is determined by the atom spontaneous emission to the open space and the widths of side peaks are largely determined by the coherent interaction between the atom and the cavity, that is, the fluorescence spectrum here is very different from that of the Mollow triplet. We also derive analytical form for the spectrum. Our experimental results agree well with theoretical calculations.