ISI Foundation, I-10133 Torino, Italy.
Phys Rev Lett. 2010 Jul 9;105(2):020503. doi: 10.1103/PhysRevLett.105.020503. Epub 2010 Jul 7.
We extend the quantum discord to continuous variable systems and evaluate Gaussian quantum discord C(ϱ) for bipartite Gaussian states. In particular, for squeezed-thermal states, we explicitly maximize the extractable information over Gaussian measurements: C(ϱ) is minimized by a generalized measurement rather than a projective one. Almost all squeezed-thermal states have nonzero Gaussian discord: They may be either separable or entangled if the discord is below the threshold C(ϱ) = 1, whereas they are all entangled above the threshold. We elucidate the general role of state parameters in determining the discord and discuss its evolution in noisy channels.
我们将量子纠缠扩展到连续变量系统，并评估了双体高斯态的高斯量子纠缠 C(ϱ)。特别地，对于压缩-热态，我们通过高斯测量来最大化可提取信息：通过广义测量而不是投影测量来最小化 C(ϱ)。几乎所有压缩-热态都具有非零的高斯量子纠缠：如果纠缠度低于阈值 C(ϱ) = 1，则它们可能是可分离的或纠缠的，而高于阈值则都是纠缠的。我们阐明了状态参数在确定纠缠中的一般作用，并讨论了它在噪声信道中的演化。
