  We propose an optomechanical scheme for reaching quantum entanglement in
vibration polaritons. The system involves $N$ molecules, whose vibrations can
be fairly entangled with plasmonic cavities. We find that the vibration-photon
entanglement can exist at room temperature and is robust against thermal noise.
We further demonstrate the quantum entanglement between the vibrational modes
through the plasmonic cavities, which shows a delocalized nature and an
incredible enhancement with the number of molecules. The underlying mechanism
for the entanglement is attributed to the strong vibration-cavity coupling
which possesses collectivity. Our results provide a molecular optomechanical
scheme which offers a promising platform for the study of noise-free quantum
resources and macroscopic quantum phenomena.
