Hierarchy in temporal quantum correlations

TL;DR

This paper establishes a hierarchy among three types of temporal quantum correlations—temporal inseparability, temporal steering, and macrorealism—highlighting their roles in quantum causality and network analysis.

Contribution

It introduces a hierarchy among temporal quantum correlations and links their quantification to measures of quantum causality and cause distinction in networks.

Findings

Hierarchy established among temporal correlations

Temporal steering as a measure of quantum causality

Application to distinguishing causes in quantum networks

Abstract

Einstein-Podolsky-Rosen (EPR) steering is an intermediate quantum correlation that lies in between entanglement and Bell non-locality. Its temporal analogue, temporal steering, has recently been shown to have applications in quantum information and open quantum systems. Here, we show that there exists a hierarchy among the three temporal quantum correlations: temporal inseparability, temporal steering, and macrorealism. Given that the temporal inseparability can be used to define a measure of quantum causality, similarly the quantification of temporal steering can be viewed as a weaker measure of direct cause and can be used to distinguish between direct cause and common cause in a quantum network.