Vacuum Rabi splitting in a semiconductor circuit QED system.

Vacuum Rabi splitting is demonstrated in a GaAs double quantum dot system coupled with a coplanar waveguide resonator. The coupling strength g, the decoherence rate of the quantum dot γ, and the decay rate of the resonator κ are derived, assuring distinct vacuum Rabi oscillation in a strong coupling regime [(g,γ,κ)≈(30,25,8.0) MHz]. The magnitude of decoherence is consistently interpreted in terms of the coupling of electrons to piezoelectric acoustic phonons in GaAs.