Einstein-Podolsky-Rosen entanglement and asymmetric steering between distant macroscopic mechanical and magnonic systems

TL;DR

This paper presents a scheme to generate long-distance hybrid EPR entanglement and asymmetric quantum steering between a mechanical oscillator and a magnon mode across a large frequency gap, with potential quantum communication applications.

Contribution

It introduces a deterministic method to establish remote phonon-magnon entanglement using electromechanical and magnonic cavities, even beyond the sideband-resolved regime.

Findings

Achieves stationary phonon-magnon EPR entanglement over ten gigahertz frequency difference.

Demonstrates the possibility of asymmetric quantum steering between macroscopic systems.

Enables applications in quantum networking and device-independent cryptography.

Abstract

We propose a deterministic scheme for establishing hybrid Einstein-Podolsky-Rosen (EPR) entanglement channel between a macroscopic mechanical oscillator and a magnon mode in a distant yttrium-iron-garnet (YIG) sphere across about ten gigahertz of frequency difference. The system consists of a driven electromechanical cavity which is unidirectionally coupled to a distant electromagnonical cavity inside which a YIG sphere is placed. We find that far beyond the sideband-resolved regime in the electromechanical subsystem, stationary phonon-magnon EPR entanglement can be achieved. This is realized by utilizing the output field of the electromechanical cavity being an intermediary which distributes the electromechanical entanglement to the magnons, thus establishing a remote phonon-magnon entanglement. The EPR entanglement is strong enough such that phonon-magnon quantum steering can be attainable in an asymmetric manner. This long-distance macroscopic hybrid EPR entanglement and steering enable potential applications not only in fundamental tests of quantum mechanics at the macro scale, but also in quantum networking and one-sided device-independent quantum cryptography based on magnonics and electromechanics.