  A technique for conditionally creating single- or multimode photon-number
states is analyzed using Bayesian theory. We consider the heralded N-photon
states created from the photons produced by an unseeded optical parametric
amplifier when the heralding detector is the time-multiplexed
photon-number-resolving detector recently demonstrated by Fitch, et al. [Phys.
Rev. A 68, 043814 (2003).] and simultaneously by Achilles, et al. [Opt. Lett.
28, 2387 (2003).]. We find that even with significant loss in the heralding
detector, fields with sub-Poissonian photon-number distributions can be
created. We also show that heralded multimode fields created using this
technique are more robust against detector loss than are single-mode fields.
