  We study by quantum Monte Carlo simulations the ground state of a
harmonically confined dipolar Bose gas with aligned dipole moments, and with
the inclusion of a repulsive two-body potential of varying range. Two different
limits can be clearly identified, namely a classical one in which the
attractive part of the dipolar interaction dominates and the system forms an
ordered array of parallel filaments, and a quantum-mechanical one, wherein
filaments are destabilized by zero-point motion, and eventually the ground
state becomes a uniform cloud. The physical character of the system smoothly
evolves from classical to quantum mechanical as the range of the repulsive
two-body potential increases. An intermediate regime is observed, in which
ordered filaments are still present, albeit forming different structures from
the ones predicted classically; quantum-mechanical exchanges of
indistinguishable particles across different filaments allow phase coherence to
be established, underlying a global superfluid response.
