[math-fun] A polarization puzzle - my solution (Eugene Salamin)

Salamin's proof is stronger than mine in the sense that it works for any linear transformation as the effect of the optics; mine only works for "normal" linear transformations. Both are valid for quantum mechanics. Meeker's objection to our proofs is somewhat scary. Both my & Salamin's impossibility proofs seem valid provided the optical device is "passive" in the sense that it sort of acts like a potential in the Schrodinger equation, rather than being part of the wavefunction -- i.e. the state of the optical device itself is assumed unaltered. Meeker's objection pertains if that state is allowed to alter. I think Meeker is correct if that were allowed.