Identification of a telecom wavelength single photon emitter in silicon

The G photoluminescence center in silicon emits single photons in the telecommunication O band and ODMR was demonstrated in its metastable triplet state. These properties make it a promising candidate as spin-photon interface for quantum networks. In this study, we determine the exact microscopic structure of the defect by calculating its magneto-optical properties. We describe a rotational motion of the interstitial silicon atom in the defect. We explain the observed fine structure of the ZPL with the rotational tunneling splitting and its isotope shift with the change in the zero-point energy of the rotation. We describe rotational and thermally activated averaging to axial symmetry in the defect properties compared to the measurement frequency. Our in-depth characterization is a key step in the optical control of the qubit state and reveals an interesting physics coupling multiple degrees of freedom of the defect.