The animations bellow show a single quantum particle represented as wavepacket diffusing to the right while being reflected off a hard wall at zero. Robin boundary conditions are used at the wall controlled by the parameter $\eta$ which can be interpreted as a phase shift. For $\eta$ negative (right animation), a bound state (i.e. non-diffusive state) exists corresponding to an effective zero-range attractive force causing the wavefunction to "stick" to the wall. As a result the diffusive properties for the two cases are essentially different and can be controlled by the parameter $\eta$. For more details check out our recent paper (10).