Coherent coupling of metamaterial resonators with dipole transitions of boron acceptors in Si

We investigate the coherent coupling of metamaterial resonators with hydrogen-like boron acceptors in Si at cryogenic temperatures. When the resonance frequency of the metamaterial, chosen to be in the range 7–9 THz, superimposes the transition frequency from the ground state of the acceptor to an excited state, Rabi splitting as large as 0.4 THz is observed. The coherent coupling shows a feature of cooperative interaction, where the Rabi splitting is proportional to the square root of the density of the acceptors. Our experiments may help to open a possible route for the investigation of quantum information processes employing strong coupling of dopants in cavities.