  Since T. Lyons invented rough path theory, one of its most successful
applications is a new proof of Freidlin-Wentzell's large deviation principle
for diffusion processes. In this paper we extend this method to the case of
pinned diffusion processes under a mild ellipticity assumption. Besides rough
path theory, our main tool is quasi-sure analysis, which is a kind of potential
theory in Malliavin calculus.
