  We demonstrate how insights gained from reformulating the problem of quantum
teleportation into one of reversing quantum operations, and designing optimum
completely positive maps for teleportation, can enable one to explore optimal
approximate reversal of quantum operations on a single qubit. In particular, we
show that the optimal approximate reversal of a generalized depolarizing
channel can be achieved using only unitary transformations. We also show that
for a quantum channel, which reveals some information about the input state,
extremal completely positive maps and not unitary transformations yield optimal
approximate reversal.
