Tomography of two-particle spin states

A new "classical" formulation of conventional quantum mechanics is used to construct a description of quantum states with spin j = 1/2 which uses only positive classical probabilities of observables instead of a complex density matrix. These probabilities are functions of points on a unit sphere which determine the directions relative to which the spin projections are measured. The proposed construction is a generalization of a system for tomography of the spin states of a single particle and may be used as a new method of measuring two-particle spin states. For pure spin states this method is exactly the same as the case of a single particle. Additional probabilities must be defined to describe mixed states. (C) 1998 American Institute of Physics. [S1063-7761(98)00508-3].