Single Artificial-Atom Lasing of a Dressed Flux Qubit

Superconducting quantum bits originally developed for quantum computation have properties similar to real atoms. Because they are micro fabricated circuits, their interaction with electromagnetic radiation can be engineered and effects known from quantum optics may be realized. In this work, a unique lasing scheme exploiting only the lowest two levels of a single artificial atom coupled to a high-quality superconducting resonator is experimentally realized. It is based on the dressing of the atom’s states by a strong signal and the associated rescaling of the relaxation. In addition, basic physical processes are discussed by a separate characterization of the artificial atom, the resonator, and their coupling. A quantum theory including dissipative processes is developed from basic superconducting effects and its applicability demonstrated by a perfect agreement with the experimental results. It gives an illustrative insight into the physics of atom-photon interaction.