Perfect quantum privacy implies nonlocality

Phys Rev Lett. 2010 Jun 11;104(23):230401. doi: 10.1103/PhysRevLett.104.230401. Epub 2010 Jun 7.

Abstract

Private states are those quantum states from which a perfectly secure cryptographic key can be extracted. They represent the basic unit of quantum privacy. In this work we show that all states belonging to this class violate a Bell inequality. This result establishes a connection between perfect privacy and nonlocality in the quantum domain.