  Analytical expressions are derived for coherent tunneling via adiabatic
passage (CTAP) in a triple well system with negligible central-well population
at all times during the transfer. It is shown that a manipulation of the depths
of the extreme-wells, correlated with the time variation of the
\emph{non-adjacent} barriers is essential for maintaining vanishing population
of the central well. The validity of our conditions are demonstrated with a
numerical solution of the time-dependent Schr\"{o}dinger equation. The transfer
process is interpreted in terms of a current through the central well.
