Generalized Stern–Gerlach experiments and the observability of arbitrary spin operators

Under the assumption that we can create in the laboratory any electromagnetic field consistent with Maxwell’s equations, it is shown that an arbitrary Hermitian operator on a spin system can be measured using a suitable generalization of the Stern–Gerlach experiment. In particular, it is shown that every proposition about the spin-1 system is verifiable, answering the challenge of Hultgren and Shimony. The analysis also reveals complications in the standard Stern–Gerlach experiment of which many physicists are apparently not aware.