**Einstein, the EPR argument, and Steering: New Perspectives from Quantum Information** - Howard Wiseman

This centenary of Einstein's annus mirabilus was also the 70th anniversary of his last great paper, the famous EPR attack on the Copenhagen interpretation (CI) of quantum mechanics (QM). It is not always appreciated that Einstein's point of attack was the nonlocality of the CI. That the CI was incomplete was the conclusion of EPR, not their starting point. In the same year, Schrödinger also pointed out the nonlocality that arises in the CI, and he called it steering. Unlike Einstein, he drew the conclusion that QM was probably wrong. In this work, we revisit these old arguments in the light of quantum information. We formalize Schrödinger's concept of steering, showing that it is a form of quantum nonlocality that is logically weaker than Bell-nonlocality but logically stronger than non-separability. For pure states, these concepts coincide. But for mixed states we present strong evidence that steering is practically (not just logically) distinct from both Bell-nonlocality and non-separability. Finally, we generalize the EPR argument to an arbitrary multi-mode Gaussian state shared by Alice and Bob, showing that the criterion for steering can be written as a simple linear matrix inequality.