  The s-wave kaon-antikaon ($K \bar{K}$) elastic scattering length is
investigated by lattice simulation using pion masses $m_\pi = 330 - 466$ MeV.
Through moving wall sources without gauge fixing, we calculate $K \bar{K}$
four-point correlation functions for isospin I=1 channel in the "Asqtad"
improved staggered fermion formulation, and observe a clear signal of
attraction, which is consistent with other pioneering lattice studies on $K
\bar{K}$ potential. Extrapolating $K \bar{K}$ scattering length to the physical
point, we obtain $m_{K} a^{I=1}_{K\bar{K}} = 0.211(33)$. These simulations are
performed with MILC gauge configurations at lattice spacing $a \approx 0.15$
fm.
