  We demonstrate a novel second-order spatial interference effect between two
indistinguishable pairs of disjoint optical paths from a single chaotic source.
Beside providing a deeper understanding of the physics of multi-photon
interference and coherence, the effect enables retrieving information on both
the spatial structure and the relative position of two distant double-pinhole
masks, in the absence of first order coherence. We also demonstrate the
exploitation of the phenomenon for simulating quantum logic gates, including a
controlled-NOT gate operation.
