1202.1598 (Sevag Gharibian)

Quantifying non-classicality with local unitary operations    [PDF]

Sevag Gharibian

We propose a measure of non-classical correlations in bipartite quantum
states based on local unitary operations. We prove the measure is non-zero if
and only if the quantum discord is non-zero; this is achieved via a new
characterization of zero discord states in terms of the state's correlation
matrix. Moreover, our scheme can be extended to ensure the same relationship
holds even with a generalized version of quantum discord in which higher-rank
projective measurements are allowed. We next derive a closed form expression
for our scheme in the cases of Werner states and (2 x N)-dimensional systems.
The latter reveals that for two-qubit states, our measure reduces to the
geometric discord [Dakic et al., PRL 105, 2010]. A connection to the CHSH
inequality is shown. We close with a characterization of all maximally
non-classical, yet separable, two-qubit states of rank at most two (with
respect to our measure, and hence also with respect to the geometric discord).

View original: http://arxiv.org/abs/1202.1598