  Using first-principles density functional theory calculations, we examined
the ground state property of LaTiO$_3$/LaAlO$_3$ superlattice. Total energy
calculations, taking account of the structural distortions, $U$ dependence, and
exchange correlation functional dependence, show that the spin and orbital
ground state can be controlled systematically by the epitaxial strain. In the
wide range of strains, ferromagnetic spin and antiferro orbital ordering are
stabilized, which is notably different from the previously reported ground
state in titanate systems. By applying large tensile strains, the system can be
transformed into an antiferromagnetic spin and ferro-orbital-ordered phase.
