  In this paper, we study the stability of two inverse boundary value problems
in an infinite slab with partial data. These problems have been studied by Li
and Uhlmann for the case of the Schrodinger equation and by Krupchyk, Lassas
and Uhlmann for the case of the magnetic Schrodinger equation. Here we quantify
the method of uniqueness proposed by Li and Uhlmann and prove a log-log
stability estimate for the inverse problems associated to the Schrodinger
equation. The boundary measurements considered in these problems are modelled
by partial knowledge of the Dirichlet-to-Neumann map: in the first inverse
problem, the corresponding Dirichlet and Neumann data are known on different
boundary hyperplanes of the slab; in the second inverse problem, they are known
on the same boundary hyperplane of the slab.
