Invariant Quantum Discord in Qubit-Qutrit Systems under Local Dephasing
  We investigate the dynamics of quantum discord and entanglement for a class of mixed qubit-qutrit states assuming that only the qutrit is under the action of a dephasing channel. We demonstrate that even though the entanglement in the qubit-qutrit state disappears in a finite time interval, partial coherence left in the system enables quantum discord to remain invariant throughout the whole time evolution. 
G. Karpat and Z. Gedik
quant-ph