Engineering two-mode continuous-variable entangled states of distant atomic spin ensembles with superconducting quantum circuits

We present an experimental feasible scheme to generate two-mode entangled states of two spatially separated atomic spin ensembles, using superconducting quantum circuits consisting of two coplanar waveguide resonators and a charge qubit. We show that, with the charge qubit as a tunable coupler and the resonator modes as a quantum bus, the collective atomic spins can be steered into a two-mode squeezed state exhibiting Einstein-Podolsky-Rosen entanglement through adiabatic following of the ground state of the system.