Measurement of spatial qubits
  In this paper we study the state determination for composite systems of two spatial qubits. We show, theoretically, that one can use the technique of quantum tomography to reconstruct the density matrixes of these systems. This tomographic reconstruction is based on the free evolution of the spatial qubits and a postelection process. 
G. Lima, F.A. Torres-Ruiz, L. Neves, A. Delgado, C. Saavedra and S.   Padua