A Condition for the Nullity of Quantum Discord

The positivity of quantum discord is shown to be equivalent to the strong subadditivity of von-Neumann entropy. This leads us to a necessary and sufficient condition characterizing the set of states with zero quantum discord. This also gives us a mathematical definition of pointer states, as they are the states with zero discord. Finally, we suggest that strong subadditivity of entropy might delineate the boundaries of the set of quantum correlations.

[1]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[2]  A. Datta.  Studies on the Role of Entanglement in Mixed-state Quantum Computation , 2008, 0807.4490.

[3]  D. Petz.  Quantum Information Theory and Quantum Statistics , 2007 .

[4]  R. Rosenfeld.  Nature , 2009, Otolaryngology--head and neck surgery : official journal of American Academy of Otolaryngology-Head and Neck Surgery.