Ab initio characterization of defect centers in silicon

In this work we report a theoretical study of color center defects in silicon. Color centers with photon emission in the telecommunication bands are promising candidates for the implementation of a quantum network between several computing nodes, this however requires long spin coherence times and a narrow linewidth for the qubit energy levels. Here we employ ab initio density functional theory to characterize W and G centers by extracting energy levels, photoluminescence spectra, zero field splitting and decoherence properties like dephasing times and fluctuations of the defect energy levels. The calculation of these properties requires, in addition to a deep understanding of the energetic structure, also a detailed knowledge of the vibronic excitations close to the defect center. We also discuss the effect of disorder on these properties and the potential applicability of these systems for quantum information applications.