Correlated Emission Lasing in Harmonic Oscillators Coupled via a Single Three-Level Artificial Atom

A single superconducting artificial atom can be used for coupling electromagnetic fields up to the single pho- ton level due to easily achieved strong coupling regime. Bringing a pair of harmonic oscillators into resonance with the transitions of a three-level atom converts atomic spontaneous processes into correlated emission dy- namics. We present experimental demonstration of two-mode correlated emission lasing in harmonic oscillators coupled via a fully controllable three-level superconducting quantum system (artificial atom). The correlation of emissions with two different colors reveals itself as equally narrowed linewiths and quenching of their mutual phase diffusion. The mutual linewidth is more than four orders of magnitude narrower than the Schawlow- Townes limit. The interference between the different color lasing fields demonstrates that the two-mode fields are strongly correlated.