  We propose a new interferometric setup which displays a completely
destructive generalized N-photon Hong-Ou-Mandel interference. The key property
of this scheme is that is does not require any optical elements like beam
splitters or integrated waveguide structures. The interference is intrinsically
produced by the evolution of N photons in free space when emitted by N
identical statistically independent single photon sources and measured by N
detectors in the far field. In this sense the setup is a most simple and
natural implementation of the Hong-Ou-Mandel interference effect, i.e., of a
completely destructive multi-photon interference produced by statistically
independent incoherent sources.
