Einstein-Podolsky-Rosen steering incarnates a useful nonclassical correlation which sits in-between entanglement and Bell nonlocality. While a number of qualitative steering criteria exist, very little has been achieved for what concerns quantifying steerability. We introduce a computable measure of steering for arbitrary bipartite Gaussian states of continuous variable systems. For two-mode Gaussian states, the measure reduces to a form of coherent information, which is proven never to exceed entanglement, and to reduce to it on pure states. We provide an operational connection between our measure and the key rate in one-sided device-independent quantum key distribution. We further prove that steering bound entangled Gaussian states by Gaussian measurements is impossible. We finally discuss how to generalise our measure to non-Gaussian states, and its connection with the degree of violation of linear variance criteria inspired by the Einstein-Podolsky-Rosen paradox.

报告人简介: Gerardo Adesso is an Associate Professor at the University of Nottingham (UK) and the head of the Quantum Correlations group, http://quantumcorrelations.weebly.com. He obtained his PhD from the University of Salerno (Italy) in 2007. He joined Nottingham in 2009 after postdoctoral positions in Salerno, Rome and Barcelona. His main interests are in the characterisation, quantification and operational interpretation of quantum correlations in composite systems, including entanglement, nonlocality, steering, and discord. He has contributed significantly to the development of quantum information theory with Gaussian states of continuous variable systems. He has published over 90 articles, delivered over 60 invited talks, and attracted over 2000 citations.