  The multimode interference technique is a simple way to study the
interference patterns found in many quantum probability distributions. We
demonstrate that this analysis not only explains the existence of so-called
"quantum carpets," but can explain the spatial distribution of channels and
ridges in the carpets. With an understanding of the factors that govern these
channels and ridges we have a limited ability to produce a particular pattern
of channels and ridges by carefully choosing the weighting coefficients c_{n} .
We also use these results to demonstrate why fractional revivals of initial
wavepackets are themselves composed of many smaller packets.
