You can bring it back as a liquid. (Classical, not superfluid) Boil-off would be a problem, however. (If you want to get fancy, you bring back a He4 tank and a

You can bring it back as a liquid. (Classical, not superfluid) Boil-off would be a problem, however. (If you want to get fancy, you bring back a He4 tank and a refrigerator, keeping the He3 liquid by boiling He4 into space) Liquid He4 has a density on the order of 125g/L at boiling point at 1atm. Don't know about He3, but even at 50g/L, that's ~20L/kg. Not nearly as bad.