  We present a new non-local updating scheme for quantum Monte Carlo
simulations, which conserves particle number and other symmetries. It allows
exact symmetry projection and direct evaluation of the equal-time Green's
function and other observables in the canonical ensemble. The method is applied
to bosonic atoms in optical lattices, neutron pairs in atomic nuclei and
electron pairs in ultrasmall superconducting grains.

Statistical Mechanics;Superconductivity;Nuclear Theory