On characterising assemblages in Einstein-Podolsky-Rosen scenarios

TL;DR

This paper investigates the characterization of quantum steering in EPR scenarios, proposing a method based on tomographically-complete measurements to distinguish non-classical assemblages and exploring their relation to almost quantum correlations.

Contribution

It introduces a novel approach to characterize assemblages in EPR scenarios using tomographic measurements and links almost quantum assemblages to macroscopic noncontextuality.

Findings

Almost quantum assemblages satisfy macroscopic noncontextuality

A subset of almost quantum correlations correspond to almost quantum assemblages

The proposed method offers insights into non-classicality in quantum steering

Abstract

Characterising non-classical quantum phenomena is crucial not only from a fundamental perspective, but also to better understand its capabilities for information processing and communication tasks. In this work, we focus on exploring the characterisation of Einstein-Podolsky-Rosen inference (a.k.a. steering): a signature of non-classicality manifested when one or more parties in a Bell scenario have their systems and measurements described by quantum theory, rather than being treated as black boxes. We propose a way of characterising common-cause assemblages from the correlations that arise when the trusted party performs tomographically-complete measurements on their share of the experiment, and discuss the advantages and challenges of this approach. Within this framework, we show that so-called almost quantum assemblages satisfy the principle of macroscopic noncontextuality, and demonstrate that a subset of almost quantum correlations recover almost quantum assemblages in this approach.