The state disturbance induced by locally measuring a quantum system yields a signature of nonclassical correlations beyond entanglement. Here, we present a detailed study of such correlations for two-qubit mixed states. To overcome the asymmetry of quantum discord and the unfaithfulness of measurement-induced disturbance (severely overestimating quantum correlations), we propose an ameliorated measurement-induced disturbance as nonclassicality indicator, optimized over joint local measurements, and we derive its closed expression for relevant two-qubit states. We study its analytical relation with discord, and characterize the maximally quantum-correlated mixed states, that simultaneously extremize both quantifiers at given von Neumann entropy: among all two-qubit states, these states possess the most robust quantum correlations against noise.
ASJC Scopus subject areas
- Mathematical Physics
- Modelling and Simulation
- Statistics and Probability
- Physics and Astronomy(all)
- Statistical and Nonlinear Physics
Girolami, D., Paternostro, M., & Adesso, G. (2011). Faithful nonclassicality indicators and extremal quantum correlations in two-qubit states. JOURNAL OF PHYSICS A-MATHEMATICAL AND THEORETICAL, 44(35), 352002. . https://doi.org/10.1088/1751-8113/44/35/352002