Optical probing of the carrier-mediated coupling of the spin of two Co atoms in a quantum dot

A direct band gap semiconductor quantum dot enables a spin-photon interface with embedded carriers or magnetic impurities, a key element in the establishment of quantum information networks. Spins of magnetic atoms carrying an orbital moment can also be interfaced with phonons and could be used to couple sound, spin, and light at the quantum level. The authors show here that injecting carriers into a quantum dot can induce correlation between two spins of distant magnetic atoms. Resonant optical access to the spin state of the two correlated atoms is conditioned by their position in the dot and by the local configuration of the strain.