  We examine a classically-chaotic system consisting of two reservoirs of
particles connected by a channel containing oscillating potential-energy
barriers. We investigate whether such a system can preferentially pump
particles from one reservoir to the other, a process often called "quantum
pumping." We show how to make a "particle diode" which under specified
conditions permits net particle pumping in only one direction. Then we examine
systems having symmetric barriers. We find that if all initial particle
energies are considered, a system with symmetric barriers cannot preferentially
pump particles. However, if only finite initial energy bands are considered,
the system can create net particle transport in either direction. We study the
system classically, semiclassically, and quantum mechanically, and find that
the quantum description cannot be fully understood without the insight gained
from classical and semiclassical analysis.
