Correlation strengths in hybrid networks

TL;DR

This paper investigates the maximal correlation strength in hybrid networks combining classical, quantum, and no-signaling sources, deriving bounds and criteria for nonlocality based on network composition.

Contribution

It introduces segmented Bell operators and tailored Bell inequalities for hybrid networks, providing benchmarks and t-nonlocality criteria for correlation strengths.

Findings

Correlation strength depends on the number of type-A measurements.

Derived upper bounds for classical, quantum, and no-signaling networks.

Introduced t-nonlocality criteria for network nonlocality detection.

Abstract

In a generic hybrid network, classical, quantum, and no-signaling sources emit local hidden variables, stabilizer states, and no-signaling systems, respectively. We investigate the maximal correlation strength as the non-classical feature in this network. Given the associated fully-quantum network of a hybrid network, we exploit the stabilizing operators of the distributed quantum state to construct segmented Bell operators and the Bell inequalities tailored to the state. We derive the upper bounds of the maximal correlation strengths in the associated full-classical, full-quantum, and fully-no-signaling networks as the benchmarks. Our study shows that the achievable correlation strength depends on the number of type-A measurements and that of nonlocal sources. We also introduce the t-nonlocality criteria, indicating that the achievable maximal correlation strength cannot modeled by the network with at least t observers with local hidden variables performing type-A measurements.