  The properties of low-density, low-energy matter wavepackets propagating
through waveguide bends are investigated. Time-dependent quantum mechanical
calculations using simple harmonic oscillator confining potentials are
performed for a range of parameters close to those accessible by recent ``atom
chip''-based experiments. We compare classical calculations based on
Ehrenfest's theorem to these results to determine whether classical mechanics
can predict the amount of transverse excitation as measured by the transverse
heating. The present results thus elucidate some of the limits for which matter
wave propagation through microstructures can be reliably considered using
classical particle motion.
