  Feedback loops are known as a versatile tool for controlling transport in
small systems, which usually have large intrinsic fluctuations. Here we
investigate the control of a temporal correlation function, the waiting time
distribution, under active and passive feedback conditions. We develop a
general formalism and then specify to the simple unidirectional transport
model, where we compare costs of open loop and feedback control and use methods
from optimal control theory to optimize waiting time distributions.
