Abstract
We extend the quantum discord to continuous variable systems and evaluate Gaussian quantum discord for bipartite Gaussian states. In particular, for squeezed-thermal states, we explicitly maximize the extractable information over Gaussian measurements: 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 , 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.
- Received 15 March 2010
DOI:https://doi.org/10.1103/PhysRevLett.105.020503
©2010 American Physical Society