  We study the von Neumann entropy of the partial trace of a system of two
two-level atoms (qubits) in a dispersive cavity where the atoms are interacting
collectively with a single mode electromagnetic field in the cavity. We make a
contrast of this entanglement entropy with the spin squeezing property of the
system. We find a close relationship between this von Neumann entropy and the
spin squeezing of the system. We observe that this entanglement entropy attains
its maximum value when the spin squeezing in the system goes to its maximum and
is zero when the spin squeezing in the system vanishes.
