  In this paper we examine the N-photon absorption properties of "N00N" states,
a subclass of path entangled number states. We consider two cases. The first
involves the N-photon absorption properties of the ideal N00N state, one that
does not include spectral information. We study how the N-photon absorption
probability of this state scales with N. We compare this to the absorption
probability of various other states. The second case is that of two-photon
absorption for an N = 2 N00N state generated from a type II spontaneous down
conversion event. In this situation we find that the absorption probability is
both better than analogous coherent light (due to frequency entanglement) and
highly dependent on the optical setup. We show that the poor production rates
of quantum states of light may be partially mitigated by adjusting the spectral
parameters to improve their two-photon absorption rates. This work has
application to quantum imaging, particularly quantum lithography, where the
N-photon absorbing process in the lithographic resist must be optimized for
practical applications.
