  We address computational issues relevant to the study of disordered quantum
mechanical systems at very low temperatures. As an example we consider the
disordered Bose- Hubbard model in three dimensions directly at the Bose-glass
to superfluid phase transition. The universal aspects of the critical behaviour
are captured by a (3 + 1) dimensional link-current model for which an efficient
'worm' algorithm is known. We present a calculation of the distribution of the
superfluid stiffness over the disorder realizations, outline a number of
important considerations for performing such estimates, and suggest a
modification of the link-current Hamiltonian that improves the numerical
efficiency of the averaging procedure without changing the universal properties
of the model.
