State reconstruction for composite systems of two spatial qubits

Abstract

Pure entangled states of two spatial qudits have been produced by using the momentum transverse correlation of the parametric down-converted photons [Phys. Rev. Lett. \textbf{94} 100501]. Here we show a generalization of this process to enable the creation of mixed states of spatial qudits and by using the technique proposed we generate mixed states of spatial qubits. We also report how the process of quantum tomography is experimentally implemented to characterize these states. This tomographic reconstruction is based on the free evolution of spatial qubits, coincidence detection and a filtering process. The reconstruction method can be generalized for the case of two spatial qudits.

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