In the Stern–Gerlach experiment, an unpolarized beam of neutral particles of spin 1/2 is directed through an inhomogeneous magnetic field (blue and red magnet), which produces separated beams of spin-up and spin-down particles. For simplicity, only the outgoing spin-up beam is shown in the graphic. This beam is then directed through a second magnet, for which the polarization can be rotated by an angle from the original. This further splits the beam (except when or ) into spin-up and spin-down beams with respect to the new polarization direction. Again, only the spin-up component is shown. The probability for a particle to emerge with spin-up (↑) or spin-down (↓) is given by and , respectively. The resulting probabilities of ↑ and ↓ are shown for five selected angles.