Asymmetric Gaussian steering: when Alice and Bob disagree

TL;DR

This paper explores asymmetric quantum steering where measurement limitations lead to different descriptions of a bipartite system, revealing fundamental asymmetries in quantum theory.

Contribution

It demonstrates theoretically that asymmetric Gaussian steering can occur with Gaussian measurements, highlighting the need to consider the entire system in certain quantum scenarios.

Findings

Asymmetric steering depends on measurement capabilities.

Gaussian measurements may be insufficient to fully characterize the system.

The intracavity nonlinear coupler can demonstrate this phenomenon.

Abstract

Asymmetric steering is an effect whereby an inseparable bipartite system can be found to be described by either quantum mechanics or local hidden variable theories depending on which one of Alice or Bob makes the required measurements. We show that, even with an inseparable bipartite system, situations can arise where Gaussian measurements on one half are not sufficient to answer the fundamental question of which theory gives an adequate description and the whole system must be considered. This phenomenon is possible because of an asymmetry in the definition of the original Einstein-Podolsky-Rosen paradox and in this article we show theoretically that it may be demonstrated, at least in the case where Alice and Bob can only make Gaussian measurements, using the intracavity nonlinear coupler.