skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Quantum Entanglement in Quasispin Models


We discuss the concept of quantum entanglement of mixed states, and its behavior in quasispin systems at finite temperature. We examine in particular the limit temperatures for different kinds of entanglement and their relation with the mean field critical temperature.

;  [1]
  1. Depto. de Fisica, Universidad Nacional de La Plata, La Plata (1900) (Argentina)
Publication Date:
OSTI Identifier:
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 884; Journal Issue: 1; Conference: 6. Latin American symposium on nuclear physics and applications, Iguazu (Argentina), 3-7 Oct 2005; Other Information: DOI: 10.1063/1.2710618; (c) 2007 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States

Citation Formats

Rossignoli, R., and Canosa, N. Quantum Entanglement in Quasispin Models. United States: N. p., 2007. Web. doi:10.1063/1.2710618.
Rossignoli, R., & Canosa, N. Quantum Entanglement in Quasispin Models. United States. doi:10.1063/1.2710618.
Rossignoli, R., and Canosa, N. Mon . "Quantum Entanglement in Quasispin Models". United States. doi:10.1063/1.2710618.
title = {Quantum Entanglement in Quasispin Models},
author = {Rossignoli, R. and Canosa, N.},
abstractNote = {We discuss the concept of quantum entanglement of mixed states, and its behavior in quasispin systems at finite temperature. We examine in particular the limit temperatures for different kinds of entanglement and their relation with the mean field critical temperature.},
doi = {10.1063/1.2710618},
journal = {AIP Conference Proceedings},
number = 1,
volume = 884,
place = {United States},
year = {Mon Feb 12 00:00:00 EST 2007},
month = {Mon Feb 12 00:00:00 EST 2007}
  • It is shown that spontaneous symmetry breaking does not modify the ground-state entanglement of two spins, as defined by the concurrence, in the XXZ chain and the transverse field Ising chain. Correlation function inequalities, valid in any dimensions for these models, are presented outlining the regimes where entanglement is unaffected by spontaneous symmetry breaking.
  • A general geometrical structure of the entanglement entropy for spatial partition of a relativistic QFT system is established by using methods of the effective gravity action and the spectral geometry. A special attention is payed to the subleading terms in the entropy in different dimensions and to behavior in different states. It is conjectured, on the base of relation between the entropy and the action, that in a fundamental theory the ground state entanglement entropy per unit area equals 1/(4G{sub N}), where G{sub N} is the Newton constant in the low-energy gravity sector of the theory. The conjecture opens amore » new avenue in analogue gravity models. For instance, in higher-dimensional condensed matter systems, which near a critical point are described by relativistic QFT's, the entanglement entropy density defines an effective gravitational coupling. By studying the properties of this constant one can get new insights in quantum gravity phenomena, such as the universality of the low-energy physics, the renormalization group behavior of G{sub N}, the statistical meaning of the Bekenstein-Hawking entropy.« less
  • We study the short-time evolution of the bipartite entanglement in quantum lattice systems with local interactions in terms of the purity of the reduced density matrix. A lower bound for the purity is derived in terms of the eigenvalue spread of the interaction Hamiltonian between the partitions. Starting from an initially separable state the purity decreases as 1-(t/{tau}){sup 2} (i.e., quadratically in time, with a characteristic timescale {tau} that is inversely proportional to the boundary size of the subsystem, that is, as an area law). For larger times an exponential lower bound is derived corresponding to the well-known linear-in-time boundmore » of the entanglement entropy. The validity of the derived lower bound is illustrated by comparison to the exact dynamics of a one-dimensional spin lattice system as well as a pair of coupled spin ladders obtained from numerical simulations.« less
  • We study entanglement dynamics in quantum Brownian motion (QBM) models. Our main tool is the Wigner function propagator. Time evolution in the Wigner picture is physically intuitive and it leads to a simple derivation of a master equation for any number of system harmonic oscillators and spectral density of the environment. It also provides generalized uncertainty relations, valid for any initial state, that allow a characterization of the environment in terms of the modifications it causes to the system's dynamics. In particular, the uncertainty relations are very informative about the entanglement dynamics of Gaussian states, and to a lesser extentmore » for other families of states. For concreteness, we apply these techniques to a bipartite QBM model, describing the processes of entanglement creation, disentanglement, and decoherence at all temperatures and time scales.« less
  • We consider a set of fully connected spin models that display first- or second-order transitions and for which we compute the ground-state entanglement in the thermodynamical limit. We analyze several entanglement measures (concurrence, Renyi entropy, and negativity) and show that, in general, discontinuous transitions lead to a jump of these quantities at the transition point. Interestingly, we also find examples where this is not the case.