Dressed-state amplification by a superconducting qubit

TL;DR

This paper demonstrates microwave signal amplification using a superconducting flux qubit in a resonator, showcasing dressed-state lasing with observed amplification, linewidth narrowing, and emission spectrum analysis, aligning well with theoretical models.

Contribution

It presents the first experimental realization of dressed-state amplification with a superconducting qubit, confirming theoretical predictions and expanding quantum optics into superconducting circuits.

Findings

Microwave signal amplification achieved with a flux qubit

Linewidth narrowing of the probe signal observed

Emission spectrum matches dressed-state theory predictions

Abstract

We demonstrate amplification of a microwave signal by a strongly driven two-level system in a coplanar waveguide resonator. The effect known from optics as dressed-state lasing is observed with a single quantum system formed by a persistent current (flux) qubit. The transmission through the resonator is enhanced when the Rabi frequency of the driven qubit is tuned into resonance with one of the resonator modes. Amplification as well as linewidth narrowing of a weak probe signal has been observed. The laser emission at the resonator's fundamental mode has been studied by measuring the emission spectrum. We analyzed our system and found an excellent agreement between the experimental results and the theoretical predictions obtained in the dressed-state model.