Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 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.

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The categories of this paper are: hep-ph
34
The categories of this paper are: chem-ph
5
The categories of this paper are: gr-qc
15
The categories of this paper are: nucl-ex
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The categories of this paper are: adap-org
2
The categories of this paper are: math
18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
4
The categories of this paper are: cond-mat