  We theoretically examine three-well interferometry in Bose-Einstein
condensates using adiabatic passage. Specifically, we demonstrate that a
fractional coherent transport adiabatic passage protocol enables stable spatial
splitting in the presence of nonlinear interactions. A reversal of this
protocol produces a coherent recombination of the BEC with a phase-dependent
population of the three wells. The effect of nonlinear interactions on the
interferometric measurement is quantified and found to lead to an enhancement
in sensitivity for moderate interaction strengths.
