  In the present paper we are interested in analyzing the pairwise entanglement
in quantum dots, as ququart systems, naturally described by the Fermi-Hubbard
model. Using the lower bound of concurrence we show the effect of the Coulomb
interaction on the pairwise entanglement and creating entanglement within the
pairs. Specifically, it is shown that the range of entanglement can be extended
to the third neighboring site for a system size of $L=4$, while for $L>4$ the
range could be created and extended to the third neighboring site by means of
the Coulomb interaction. A rigorous description of the pairs is given in terms
of a local half filled state associated to each pair with an electron number
$N=2$ and a spin $S=0$. A thorough study of this state provides a proper
explanation related to the pairwise entanglement, namely its amount and its
behavior under the effect of the Coulomb interaction as well as the system's
size.
