  We study the quantum entanglement of coupled Pais-Uhlenbeck oscillators using
the formalism of thermo-field dynamics. The entanglement entropy is computed
for the specific cases of two and a ring of $N$ coupled Pais-Uhlenbeck
oscillators of fourth order. It is shown that the entanglement entropy depends
on the temperatures, frequencies and coupling parameters of the different
degrees of freedom corresponding to harmonic oscillators. We also make remarks
on the appearance of instabilities of higher-derivative oscillators in the
context of AdS/CFT correspondence. Finally, we advert to the information
geometry theory by calculating the Fisher information metric for the considered
system of coupled oscillators.
