We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple here quantum mechanical toy models for theories containing negative norm states.We define a single ghost-spin as in [20] as a 2-state spin variable with an indefinite inner product in the state space.We find that whenever the spin sector is disentangled from the ghost-spin sector (both of which could be entangled within themselves), the reduced density matrix obtained by tracing over all the ghost-spins gives rise to positive entanglement entropy for positive norm states, while negative norm states have an entanglement entropy with a negative real part and a constant imaginary part.However when the spins are entangled with the ghost-spins, there are new entanglement patterns in general.
For systems where the number of ghost-spins is even, it is possible to find subsectors of the Hilbert space anodized pearl price xbox where positive norm states always lead to positive entanglement entropy after tracing over the ghost-spins.With an odd number of ghost-spins however, we find that there always exist positive norm states with negative real part for entanglement entropy after tracing over the ghost-spins.