4 research outputs found
Spotlighting quantum critical points via quantum correlations at finite temperatures
We extend the program initiated in [T. Werlang et al., Phys. Rev. Lett. 105,
095702 (2010)] in several directions. Firstly, we investigate how useful
quantum correlations, such as entanglement and quantum discord, are in the
detection of critical points of quantum phase transitions when the system is at
finite temperatures. For that purpose we study several thermalized spin models
in the thermodynamic limit, namely, the XXZ model, the XY model, and the Ising
model, all of which with an external magnetic field. We compare the ability of
quantum discord, entanglement, and some thermodynamic quantities to spotlight
the quantum critical points for several different temperatures. Secondly, for
some models we go beyond nearest-neighbors and also study the behavior of
entanglement and quantum discord for second nearest-neighbors around the
critical point at finite temperature. Finally, we furnish a more quantitative
description of how good all these quantities are in spotlighting critical
points of quantum phase transitions at finite T, bridging the gap between
experimental data and those theoretical descriptions solely based on the
unattainable absolute zero assumption.Comment: 11 pages, 12 figures, RevTex4-1; v2: published versio
Quantum correlations in a few-atom spin-1 Bose-Hubbard model
We study the thermal quantum correlations and entanglement in spin-1 Bose-Hubbard model with two and three particles. While we use negativity to calculate entanglement, more general non-classical correlations are quantified using a new measure based on a necessary and sufficient condition for zero-discord state. We demonstrate that the energy level crossings in the ground state of the system are signalled by both the behavior of thermal quantum correlations and entanglement