Quantifying non-classicality with local unitary operations

Understand

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.