Based upon standard angular momentum theory, we develop a framework to investigate polarization squeezing and multipartite entanglement of a quantum light field. Both mean polarization and variances of the Stokes parameters are obtained analytically, with which we study recent observation of triphoton states [L. K. Shalm {it et al}, Nature textbf{457}, 67 (2009)]. Our results show that the appearance of maximally entangled NOON states accompanies with a flip of mean polarization and can be well understood in terms of quantum Fisher information.
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