Sound-Based Analogue of Cavity Quantum Electrodynamics in Silicon

A quantum mechanical superposition of a long-lived, localized phonon and a matter excitation is described. We identify a realization in strained silicon: a low-lying donor transition (P or Li) driven solely by acoustic phonons at wavelengths where high-Q phonon cavities can be built. This phonon-matter resonance is shown to enter the strongly coupled regime where the "vacuum" Rabi frequency exceeds the spontaneous phonon emission into noncavity modes, phonon leakage from the cavity, and phonon anharmonicity and scattering. We introduce a micropillar distributed Bragg reflector Si/Ge cavity, where Q similar or equal to 10(5)-10(6) and mode volumes V less than or similar to 25 lambda(3) are reachable. These results indicate that single or many-body devices based on these systems are experimentally realizable.