  A scheme is presented for the adiabatic transfer of average fluctuation in
the phonon number between two membranes in an optical cavity. We show that by
driving the cavity modes with external time-delayed pulses, one can obtain an
effect analogous to stimulated Raman adiabatic passage (STIRAP) in the atomic
systems. In this adiabatic processes the population is trapped between two
states by creating a dark state.The adiabatic transfer of fluctuation from one
membrane to the other is attained through a 'dark' mode, that is robust against
decay of the mediating cavity mode.The results are supported with analytical
and numerical calculations with experimentally feasible parameters.
