All quantum states useful for teleportation are nonlocal resources

Understanding the relation between the different forms of inseparability in quantum mechanics is a longstanding problem in the foundations of quantum theory and has implications for quantum information processing. Here we make progress in this direction by establishing a direct link between quantum teleportation and Bell nonlocality. In particular, we show that all entangled states which are useful for teleportation are nonlocal resources, i.e., lead to deterministic violation of Bell's inequality. Our result also extends the phenomenon of superactivation of quantum nonlocality, recently proven by C. Palazuelos [Phys. Rev. Lett. 109, 190401 (2012)], and suggests that the latter might in fact be more general than initially thought.

Figure 1

Nonlocal properties of the isotropic state (5). This state is separable for $F\le F_s$, has a local model for $F\le F_L$ [28], and is known to violate a Bell inequality for $F_L<F_{NL}<F$ [29]. Here we show that several copies of the isotropic state are nonlocal if it is entangled, that is, if $F_s<F$. The state is useful for teleportation down to the separability limit $F_s$.