  Nitrogen-vacancy center in diamond is a solid state defect qubit with
favorable coherence time up to room temperature which could be harnessed in
several quantum enhanced sensor and quantum communication applications, and has
a potential in quantum simulation and computing. The quantum control largely
depends on the intricate details about the electronic structure and states of
the nitrogen-vacancy center, radiative and non-radiative rates between these
states and the coupling of these states to external spins, electrical, magnetic
and strain fields and temperature. In this review paper it is shown how first
principles calculations contributed to understanding the properties of
nitrogen-vacancy center, and will be briefly discussed the issues to be solved
towards full \emph{ab initio} description of solid state defect qubits.
