The quantum harmonic oscillator is a particle in a bowl-shaped potential — the quantum version of a mass on a spring. Its eigenstates are labeled nx, ny, nz: how many times the wavefunction crosses zero along each axis.
The energy depends only on the total N = nx+ny+nz, so states like 2,0,0 and 1,1,0 share an energy level — same energy, different shape.
Unlike a single eigenstate (which never changes), this plot shows a superposition of states A and B, with weights cycling as cos t and sin t. The cloud morphs continuously from pure A, through mixtures, to pure B and back.
A real superposition of two energy levels oscillates just like this, at a rate set by the energy difference — this is literally how quantum states move.
Brightness follows the probability of finding the particle there. Blue marks regions where the wavefunction is positive, red where it is negative. Dark planes are nodes — the zero crossings counted by nx, ny, nz.
The Slice and Cutaway displays expose structure hidden inside the cloud, and lowering the brightness thins it.