# Engineering asymmetric steady-state Einstein-Podolsky-Rosen steering in macroscopic hybrid systems

## TL;DR

This paper proposes a scheme to generate and control asymmetric Einstein-Podolsky-Rosen steering between macroscopic oscillators in hybrid quantum systems, even with thermal noise, advancing quantum network capabilities.

## Contribution

It introduces a cascaded hybrid system setup with unidirectional light coupling to enhance and control asymmetric quantum steering between distant macroscopic objects.

## Key findings

- Efficient unconditional steady-state EPR steering achieved.
- Steering asymmetry can be actively controlled via unidirectional coupling.
- Scheme remains effective despite thermal noise and optical losses.

## Abstract

Generation of quantum correlations between separate objects is of significance both in fundamental physics and in quantum networks. One important challenge is to create the directional "spooky action-at-a-distanc" effects that Schr\"{o}dinger called "steering" between two macroscopic and massive objects. Here, we analyze a generic scheme for generating steering correlations in cascaded hybrid systems in which two distant oscillators with effective masses of opposite signs are coupled to a unidirectional light field, a setup which is known to build up quantum correlations by means of quantum back-action evasion. The unidirectional coupling of the first to the second oscillator via the light field can be engineered to enhance steering in both directions and provides an active method for controlling the asymmetry of steering. We show that the resulting scheme can efficiently generate unconditional steady-state Einstein-Podolsky-Rosen steering between the two subsystems, even in the presence of thermal noise and optical losses. As a scenario of particular technological interest in quantum networks, we use our scheme to engineer enhanced steering from an untrusted node with limited tunability (in terms of interaction strength and type with the light field) to a trusted, highly tunable node, hence offering a path to implementing one-sided device-independent quantum tasks.