Entangled spins and ghost-spins

Autor: Dileep P. Jatkar, K. Narayan
Jazyk: angličtina
Rok vydání: 2017
Předmět:
Zdroj: Nuclear Physics B, Vol 922, Iss C, Pp 319-345 (2017)
Druh dokumentu: article
ISSN: 0550-3213
1873-1562
DOI: 10.1016/j.nuclphysb.2017.07.002
Popis: We study patterns of quantum entanglement in systems of spins and ghost-spins regarding them as simple 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 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.
Databáze: Directory of Open Access Journals
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