Testing quantum correlations versus single-particle properties within Leggett's model and beyond

Understand

Quantum theory predicts and experiments confirm that nature can produce correlations between distant events that are nonlocal in the sense of violating a Bell inequality.

• Nevertheless, Bell's strong sentence {\it Correlations cry out for explanations} remains relevant.
• The maturing of quantum information science and the discovery of the power of nonlocal correlations, e.g.
• for cryptographic key distribution beyond the standard Quantum Key Distribution schemes, strengthen Bell's wish and make it even more timely.