Groupoid Quantization of Loop Spaces
  We review the various contexts in which quantized 2-plectic manifolds are expected to appear within closed string theory and M-theory. We then discuss how the quantization of a 2-plectic manifold can be reduced to ordinary quantization of its loop space, which is a symplectic manifold. We demonstrate how the latter can be quantized using groupoids. After reviewing the necessary background, we present the groupoid quantization of the loop space of R^3 in some detail. 
Christian Saemann and Richard J. Szabo
hep-th math-ph math.MP