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Should we care about quantum discord?


Quantum bipartite systems can be correlated in various ways.  For pure states, the total  correlation can be quantified using mutual information while the entanglement entropy can be used to quantify the 'quantum correlation'.  For mixed states the situation is not as clear cut.  First, there is no unique measure of entanglement.  Second, there are some tasks involving bipartite separable state that have no classical analogue.  The 'quantum part' of the correlation can therefore be quantified in different ways depending on the task, these can be entanglement monotones or more general quantum correlation measures that do not vanish for separable states, e.g. discord.

In this talk I will begin with a brief overview of the mathematical properties of quantum discord and similar quantities.  I will then give some physical examples of where these quantities can be useful and some intuition on where they are probably useless.