  We study the $D$-dimensional high-density correlation energy $\Ec$ of the
singlet ground state of two electrons confined by a harmonic potential with
Coulombic repulsion. We allow the harmonic potential to be anisotropic, and
examine the behavior of $\Ec$ as a function of the anisotropy $\alpha^{-1}$. In
particular, we are interested in the limit where the anisotropy goes to
infinity ($\alpha\to0$) and the electrons are restricted to a lower-dimensional
space. We show that tuning the value of $\alpha$ from 0 to 1 allows a smooth
dimensional interpolation and we demonstrate that the usual model, in which a
quantum dot is treated as a two-dimensional system, is inappropriate. Finally,
we provide a simple function which reproduces the behavior of $\Ec$ over the
entire range of $\alpha$.
