Entanglement and Correlation in Kondo Impurity Systems

Nanotechnology has made it possible to fabricate electronic devices in which it is possible to manipulate and tune quantum states. The paper studies quantum entanglement in Kondo impurity systems. Experimental realization occurs in pairs of quantum dots and in endohedral fullerenes inside carbon nanotubes. Competition of many-body effects plays a very important role in determining quantum entanglement of two localized impurity spins. The reduced density matrix shows that the two spins are in a Werner state with probability coefficients being a function of spin-spin correlation. It is found that to be entangled the two spins need a minimum nonzero anti-ferromagnetic correlation. How the entanglement in the whole system is shared was discussed.