We present a simple model together with its physical implementation which
allows one to generate multipartite entanglement between several spatial modes
of the electromagnetic field. It is based on parametric down-conversion with N
pairs of symmetrically-tilted plane waves serving as a pump. The
characteristics of this spatial entanglement are investigated in the cases of
zero as well as nonzero phase mismatch. Furthermore, the phenomenon of
entanglement localization in just two spatial modes is studied in detail and
results in an enhancement of the entanglement by a factor square root of N.Comment: 7 pages, 2 figure
