Description of thermal entanglement with the static path plus random-phase approximation
- Departamento de Fisica-IFLP, Universidad Nacional de La Plata, C.C.67, La Plata (1900) (Argentina)
We discuss the application of the static path plus random-phase approximation (SPA+RPA) and the ensuing mean field+RPA treatment to the evaluation of entanglement in composite quantum systems at finite temperature. These methods involve just local diagonalizations and the determination of the generalized collective vibrational frequencies. As an illustration, we evaluate the pairwise entanglement in a fully connected XXZ chain of n spins at finite temperature in a transverse magnetic field b. It is shown that already the mean field+RPA provides an accurate analytic description of the concurrence below the mean field critical region (vertical bar b vertical bar <b{sub c}), exact for large n, whereas the full SPA+RPA is able to improve results for finite systems in the critical region. It is proven as well, that for T>0 weak entanglement also arises when the ground state is separable (vertical bar b vertical bar >b{sub c}), with the limit temperature for pairwise entanglement exhibiting quite distinct regimes for vertical bar b vertical bar <b{sub c} and vertical bar b vertical bar >b{sub c}.
- OSTI ID:
- 21011385
- Journal Information:
- Physical Review. A, Vol. 76, Issue 2; Other Information: DOI: 10.1103/PhysRevA.76.022310; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1050-2947
- Country of Publication:
- United States
- Language:
- English
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