Cavity mediated interactions and strong entanglement between YIG samples without using intrinsic nonlinearities.

A question attracting great attention is the possibility of quantum entanglement between macroscopic systems. Several systems like cold atomic ensembles; opto and electromechanical systems have been reported. It turns out that the magnetic systems like the excitations in YIG spheres in cavities could be excellent candidates for the quantum information tasks.
We study this new platform for producing quantum characteristics. In particular we present a novel scheme to generate an entangled pair of yttrium iron garnet (YIG) samples in a cavity system. A novel aspect of our proposal is that it does not involve any nonlinearities which are typically very weak. This is against the conventional wisdom which necessarily requires strong Kerr like nonlinearity. Our key idea, which leads to entanglement, is to drive the cavity by a weak strictly quantum field like squeezed vacuum field which can be generated by a flux-driven Josephson parametric amplifier (JPA). The two YIG samples interact via the cavity. We demonstrate a high degree of macroscopic entanglement that can survive up to temperatures like 300-500mK. The entanglement is tested using several different quantitative criteria. We also find the optimal parameter regime for entanglement.