  The entanglement at finite temperatures are analyzed by using thermal models
for colored quarks making up the hadron physical states. We have found that
these quantum correlations entirely vanish at $T_c\geq m_q/\ln(1.5)$. For
temperatures larger than $T_c$ the correlations are classical. Also we worked
out the entanglement for the transverse Ising spin chain. In dependence on both
temperature $T$ and transverse field $\lambda$ we can identify a certain
region, where the quantum effects are likely to dominate the system. We suggest
the mutual information as a quantitative measure for the correlations in ground
state.
