Survival of continuous variable entanglement over long distances

Abstract

Any quantum system, in interacting with the external classical environment, slowly loses its quantumness and entanglement degrades. In this paper, we experimentally found that, even in the presence of a strong decoherence, the state generated by a sub-threshold type-II optical parametric oscillator never disentangles, keeps breaking the quantum limit for the discord and, as a resource for quantum teleportation of a coherent state, would allow us, in principle, to realize quantum teleportation over an infinitely long Gaussian channel.