  Quantum discord is a measure of the quantumness of correlations. After
reviewing its different versions and properties, we apply it to the questions
of quantum information processing. First we show that changes in discord in the
processed unentangled states indicate the need for entanglement in the
distributed implementation of quantum gates. On the other hand, it was shown
that zero system-environment discord is a necessary and sufficient condition
for applicability of the standard completely positive description of the
system's evolution. We demonstrate that this result does not translate into
useful quantum process tomography. Depending on the details of the preparation
procedure only absence of any initial correlations may guarantees consistency
of the process tomography.
