  Using advanced first-principles calculations we predict that the non-polar
SrTiO$_3$/SrZrO$_3$ (001) interface, designed as either thin SrZrO$_3$ film
deposited on SrTiO$_3$ or short-period (SrTiO$_3$)$_m$/(SrZrO$_3$)$_n$
superlattice, host a 2-dimensionally confined electron gas. Mobile electron
charge due to native impurities, field-effect, or modulation doping remains
tightly trapped at the interface. Key ingredients for this occurrence are a)
the peculiar chemistry of 3d orbitals, b) the large band offset at
titanate-zirconate interface.
