Thermal tripartite quantum correlations: quantum discord and entanglement perspectives

We investigate thermal tripartite quantum correlations for a spin star network and for a new extended version of it. In a spin star network, three peripheral spins interact with the central spin identically while in extended spin star network, three peripheral spins interact with two central spatially separated spins in the same way. We exploit the method of [C.C. Rulli, M.S. Sarandy, Phys. Rev. A 84, 042109 (2011)] to evaluate the tripartite quantum discord (TQD) and the method of [M. Li, S. Fei, Z. Wang, Rep. Math. Phys 65, 289 (2010)] called as lower bound of tripartite concurrence (LBTC) to evaluate the tripartite entanglement (TE) of the the peripheral parties in both systems. It is found that thermal TQD is much more robust than thermal TE as a function of temperature T. Also, the peripheral parties of the extended spin star network, in comparison with those of the spin star one, can exhibit higher values of TQD at T > 0. This, indeed, motivates us to realise improved quantum information and quantum computation tasks at finite temperatures