Witnessing nonclassical multipartite states

Journal Article · Sat Oct 15 04:00:00 EDT 2011 · Physical Review. A

DOI:https://doi.org/10.1103/PHYSREVA.84.042123· OSTI ID:22080339

Saguia, A; Rulli, C C; Oliveira, Thiago R. de; Sarandy, M S ^[1]

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1. Instituto de Fisica, Universidade Federal Fluminense, Avenida General Milton Tavares de Souza s/n, Gragoata, 24210-346 Niteroi, Rio de Janeiro (Brazil)

We investigate a witness for nonclassical multipartite states based on their disturbance under local measurements. The witness operator provides a sufficient condition for nonclassicality that coincides with a nonvanishing global quantum discord, but it does not demand an extremization procedure. Moreover, for the case of Z{sub 2}-symmetric systems, we rewrite the witness in terms of correlation functions so that classicality is found to necessarily require either vanishing magnetization in the invariant axis or isotropy of the two-point function in the transverse spin plane. We illustrate our results in quantum spin chains, where a characterization of factorized ground states (with spontaneously broken Z{sub 2} symmetry) is achieved. As a by-product, the witness is also shown to indicate a second-order quantum phase transitions, which is illustrated for both the XY and the Ashkin-Teller spin chains.

• OSTI ID: 22080339
• Journal Information: Physical Review. A, Journal Name: Physical Review. A Journal Issue: 4 Vol. 84; ISSN 1050-2947; ISSN PLRAAN
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
CORRELATION FUNCTIONS
GROUND STATES
ISOTROPY
MAGNETIZATION
PHASE TRANSFORMATIONS
SPIN
SYMMETRY