  The quantum dynamics of a particle in the Modified P\"oschl-Teller potential
is derived from the group $SL(2,R)$ by applying a Group Approach to
Quantization (GAQ). The explicit form of the Hamiltonian as well as the ladder
operators is found in the enveloping algebra of this basic symmetry group. The
present algorithm provides a physical realization of the non-unitary,
finite-dimensional, irreducible representations of the $SL(2,R)$ group. The
non-unitarity manifests itself in that only half of the states are
normalizable, in contrast with the representations of SU(2) where all the
states are physical.
