  We have performed experimental quantum state tomography of NOON states with
up to four photons. The measured states are generated by mixing a classical
coherent state with spontaneous parametric down-conversion. We show that this
method produces states which exhibit a high fidelity with ideal NOON states.
The fidelity is limited by the overlap of the two-photon down-conversion state
with any two photons originating from the coherent state, for which we
introduce and measure a figure of merit. A second limitation on the fidelity
set by the total setup transmission is discussed. We also apply the same
tomography procedure for characterizing correlated photon hole states.
