  In order to witness multipartite correlations beyond pairwise entanglement,
spin-squeezing parameters are analytically calculated for a spin ensemble in a
collective initial state under three different decoherence channels. It is
shown that, in analogy to pairwise entanglement, the spin squeezing described
by different parameters can suddenly become zero at different vanishing times.
This finding shows the general occurrence of sudden vanishing phenomena of
quantum correlations in many-body systems, which here is referred to as
spin-squeezing sudden death (SSSD). It is shown that the SSSD usually occurs
due to decoherence and that SSSD never occurs for some initial states in the
amplitude-damping channel. We also analytically obtain the vanishing times of
spin squeezing.

Quantum Physics