  A single superconducting artificial atom provides a unique basis for coupling
electromagnetic fields and photons hardly achieved with a natural atom.
Bringing a pair of harmonic oscillators into resonance with transitions of the
three-level atom converts atomic spontaneous processes into correlated emission
dynamics. We demonstrate two-mode correlated emission lasing on harmonic
oscillators coupled via the fully controllable three-level artificial atom.
Correlation of two different color emissions reveals itself as equally narrowed
linewiths and quench 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 the
two-mode fields are strongly correlated.
