title: Optimality of Gaussian discord.
abstract: In this Letter we exploit the recently solved conjecture on the bosonic minimum output entropy to show the optimality of Gaussian discord, so that the computation of quantum discord for bipartite Gaussian states can be restricted to local Gaussian measurements. We prove such optimality for a large family of Gaussian states, including all two-mode squeezed thermal states, which are the most typical Gaussian states realized in experiments. Our family also includes other types of Gaussian states and spans their entire set in a suitable limit where they become Choi matrices of Gaussian channels. As a result, we completely characterize the quantum correlations possessed by some of the most important bosonic states in quantum optics and quantum information.
authors.affiliation: Computer Science, University of York, York YO10 5GH, United Kingdom.
authors.forename: Stefano
authors.initials: S
authors.lastname: Pirandola
authors.affiliation: Computer Science, University of York, York YO10 5GH, United Kingdom.
authors.forename: Gaetana
authors.initials: G
authors.lastname: Spedalieri
authors.affiliation: Computer Science, University of York, York YO10 5GH, United Kingdom.
authors.forename: Samuel L
authors.initials: SL
authors.lastname: Braunstein
authors.affiliation: Ecole Polytechnique de Bruxelles, CP 165, Université Libre de Bruxelles (ULB), 1050 Brussels, Belgium.
authors.forename: Nicolas J
authors.initials: NJ
authors.lastname: Cerf
authors.affiliation: Research Laboratory of Electronics & Department of Mechanical Engineering, MIT, Cambridge, Massachusetts 02139, USA.
authors.forename: Seth
authors.initials: S
authors.lastname: Lloyd