  We present a predictive and general approach to investigate near-field energy
transfer processes between localized defects in semiconductors, which couples
first principle electronic structure calculations and a nonrelativistic quantum
electrodynamics description of photons in the weak-coupling regime. We apply
our approach to investigate an exemplar point defect in an oxide, the F center
in MgO, and we show that the energy transfer from a magnetic source, e.g., a
rare earth impurity, to the vacancy can lead to spin non conserving long-lived
excitation that are dominant processes in the near field, at distances relevant
to the design of photonic devices and ultra-high dense memories. We also define
a descriptor for coherent energy transfer to predict geometrical configurations
of emitters to enable long-lived excitations, that are useful to design optical
memories in semiconductor and insulators.
