QuantumPhysics.dvi

probability spinsSx=± ̄h/2. The third set-up shows how successive SG apparatus inz,x

and then again inzdirections regenerate spins withSz=− ̄h/2 from an incoming beam of

purelySz= + ̄h/2.

All these phenomena are accounted for quantitatively by describing the spin as a two-state

quantum system, built on a two-dimensional complex vector space with an inner product to

yield the transition amplitudes.