Quantum polarization properties of two-mode energy eigenstates
  We show that any pure, two-mode, $N$-photon state with $N$ odd or equal to two can be transformed into an orthogonal state using only linear optics. According to a recently suggested definition of polarization degree, this implies that all such states are fully polarized. This is also found to be true for any pure, two-mode, energy eigenstate belonging to a two-dimensional SU(2) orbit. Complete two- and three-photon bases whose basis states are related by only phase shifts or geometrical rotations are also derived. 
Anita Sehat, Jonas S\"oderholm, Gunnar Bj\"ork, Pedro Espinoza, Andrei   B. Klimov, and Luis L. S\'anchez-Soto