  In this article we present a calculation of the $bb\bar{b}\bar{b}$ tetraquark
ground-state energy using a diffusion Monte Carlo method to solve the
non-relativistic many-body system. The static potential for the four quark
system is chosen to align with the flux-tube picture of QCD. Using this
approach, we find that the $0^{++}$ state has a mass of $18.69\pm
0.03~\mbox{GeV}$, which is around 100 MeV below twice the $\eta_b$ mass. This
bound state can behave as a four-lepton resonance via its decay to
$\Upsilon(1S) \Upsilon(1S)^* \rightarrow \ell^+ \ell^- \ell^+ \ell^-$.
