  The ground-state phase properties of a two-dimensional Bose system with
dipole-dipole interactions is studied by means of quantum Monte Carlo
techniques. Limitations of mean-field theory in a two-dimensional geometry are
discussed. A quantum phase transition from gas to solid is found. Crystal is
tested for existence of a supersolid in the vicinity of the phase transition.
Existence of mesoscopic analogue of the off-diagonal long-range order is shown
in the one-body density matrix in a finite-size crystal. Non-zero superfluid
fraction is found in a finite-size crystal, the signal being dramatically
increased in presence of vacancies.
