  Using $N=1+1$ supersymmetric extension of the three-dimensional gravity with
torsion, we show that a generic black hole has no exact supersymmetries, the
extremal black hole has only one, while the zero-energy black hole has two.
Combining these results with the asymptotic supersymmetry algebra, we are
naturally led to interpret the zero-energy black hole as the ground state of
the Ramond sector, and analogously, the anti-de Sitter solution as the ground
state of the Neveau-Schwartz sector.
