  We first-quantize the superparticle describing free 10D IIB supergravity on
AdS_5xS^5. We choose the worldline coordinate to be a combination of the bulk
(spatial) coordinates of anti de Sitter space and the sphere. The Hamiltonian
is independent of this "time" and the fermions. On the boundary, the
representation of PSU(2,2|4) becomes that of projective superspace. The
prepotential propagator reproduces the known field-strength one.
