  We describe an experimental demonstration of a novel three-photon NOON state
generator using a single source of photons based on spontaneous parametric
down-conversion (SPDC). The three-photon number-entangled state is
deterministically generated by the detection of a heralding photon.
Interference fringes measured with an emulated three-photon absorber reveal the
three-photon de Broglie wavelength and exhibit visibility > 70% without
background subtraction.
