Metrological measures of non-classical correlations
  Non-classical correlations denote the ways in which quantum systems can be correlated beyond what is possible in classical physics. They include but are not limited to entanglement: non-entangled states can also exhibit forms of non-classical correlations. We here review the literature on metrological measures of non-classical correlations and show how they relate to increased probe sensitivity in quantum metrology protocols such as interferometric parameter estimation and state discrimination. 
Pieter Bogaert and Davide Girolami
quant-ph