Let's look at the example of a one-dimensional nonrelativistic particle with a 2D (i.e., two states) internal degree of freedom called "spin" (it's not really spin because "real" spin is a property of 3D particles). Let b be an operator which transforms a "spin up" particle into a "spin down" particle. Its adjoint b † † then transforms a spin down particle into a spin up particle; the operators are normalized such that the anticommutator { b , b † † } = 1 . And of course, b 2 = 0 . Let p be the momentum of the particle and x be its position with [ x , p ] = i . Let W (the " superpotential ") be an arbitrary complex analytic function of x and define the supersymmetric operators