Any superfluid can theoretically act as a quantum solvent. In practice, the only viable superfluid medium that can be used is helium-4, and it has been successfully accomplished in controlled conditions.
Any inhomogeneity in the bulk superfluid medium will tend to aggregate together, encapsulated by a quantum solvation shell. This consists of a region of non-superfluid helium-4 atoms that surround the molecule(s) and exhibit adiabatic following around the centre of gravity of the whole object. Due to the frictionless nature of the superfluid medium, this quantum solvation shell then proceeds to act very much like a nanoscopic ball bearing, allowing effectively complete rotational freedom of the solvated chemical species. The only caveat to this is the necessity of altering the rotational constant of the species to compensate for the higher mass entailed by the quantum solvation shell.
Quantum solvation has so far been achieved with a number of organic, inorganic and organometallic compounds, and it has been speculated that as well as the obvious use in the field of spectroscopy, quantum solvents could be used as tools in nanoscale chemical engineering, perhaps to manufacture components for use in nanotechnology.
