Activation of Non-Local Quantum Resources

TL;DR

This paper demonstrates how certain quantum states, individually non-violating Bell inequalities, can exhibit non-locality when combined, revealing new activation phenomena in quantum non-locality.

Contribution

It introduces specific two-qubit states that activate Bell inequality violations through tensor products, and provides methods to identify non-locality activation in various Bell scenarios.

Findings

Two states that do not violate CHSH individually but do when combined.

A CHSH-local state that becomes violating when two copies are used.

Tools for finding non-locality activation in different Bell scenarios.

Abstract

We find two two-qubit states such that any number of copies of one state or the other cannot violate the CHSH Bell inequality. However, their tensor product can produce a CHSH violation of at least 2.023. We also identify a CHSH-local state such that two copies of it are CHSH-violating. The tools employed here can be easily adapted to find instances of non-locality activation in arbitrary Bell scenarios.