  We study Wigner function of a system describing entanglement of two
cat-states. Quantum interferece arising due to entanglement is shown to produce
sub-Planck structures in the phase-space plots of the Wigner function. Origin
of these structures in our case depends on entanglement unlike those in Zurek
\cite{Zurek}. It is argued that the entangled cat-states are better suited for
carrying out precision measurements.
