  For the optimal control problem governed by elliptic equations with
interfaces, we present a numerical method based on the Hansbo's Nitsche-XFEM.
We followed the Hinze's variational discretization concept to discretize the
continuous problem on a uniform mesh. We derive optimal error estimates of the
state, co-state and control both in mesh dependent norm and L2 norm. In
addition, our method is suitable for the model with non-homogeneous interface
condition. Numerical results confirmed our theoretical results, with the
implementation details discussed.
