Quantum resources for hybrid communication via qubit-oscillator states

We investigate a family of qubit-oscillator states as resources for hybrid quantum communication. They result from a mechanism of qubit-controlled displacement on the oscillator. For large displacements, we obtain analytical formulas for entanglement and other nonclassical correlations, such as entropic and geometric discord, in those states. We design two protocols for quantum communication using the considered resource states: a hybrid teleportation and a hybrid remote-state preparation. The latter, in its standard formulation, is shown to have a performance limited by the initial mixedness of the oscillator, echoing the behavior of the geometric discord. If one includes a further optimization over nonunitary correcting operations performed by the receiver, the performance is improved to match that of teleportation, which is directly linked to the amount of entanglement. Both protocols can then approach perfect efficiency even if the oscillator is originally highly thermal. We discuss the critical implications of these findings for the interpretation of general quantum correlations. © 2012 American Physical Society.