(Left) In a spin-1/2 or other two-level system, any state can be built from a superposition of a spin-up and spin-down state (blue arrows). This superposition corresponds to a point on a unit sphere, defined by the vector n.
(Right) Planar projection of the north hemisphere of a spherical representation of Majorana stars for a spin J=25. The cloudy regions represent the probability distribution for the spin wave function. In Bruno’s picture, this probability distribution is analogous to the density of a classical gas that is repelled from the Majorana stars.
Credits: (Left) APS/Carin Cain; (Right) Courtesy P. Bruno/ESRF