20 Apr 2007 | H. M. Wiseman, S. J. Jones, and A. C. Doherty
The paper by H. M. Wiseman, S. J. Jones, and A. C. Doherty revisits the concept of steering, introduced by Schrödinger in 1935 as a generalization of the EPR paradox for arbitrary pure bipartite entangled states and measurements. The authors provide an operational definition of steering and prove that steerable states are a strict subset of entangled states and a strict superset of states that can exhibit Bell-nonlocality. They derive a linear matrix inequality for Gaussian states to determine steerability and relate it to the original EPR paradox. The paper also explores the hierarchy of nonlocal properties, showing that steerability is stronger than nonseparability but weaker than Bell-nonlocality. The authors analyze Werner states and isotropic states to illustrate these hierarchies and derive conditions for steerability in these families. Additionally, they investigate Gaussian states and provide a linear matrix inequality for steerability under Gaussian measurements. The paper concludes with open questions regarding asymmetric states, the utility of steerability in tasks beyond the defining one, and the existence of steering analogs of Bell-operators and entanglement witnesses.The paper by H. M. Wiseman, S. J. Jones, and A. C. Doherty revisits the concept of steering, introduced by Schrödinger in 1935 as a generalization of the EPR paradox for arbitrary pure bipartite entangled states and measurements. The authors provide an operational definition of steering and prove that steerable states are a strict subset of entangled states and a strict superset of states that can exhibit Bell-nonlocality. They derive a linear matrix inequality for Gaussian states to determine steerability and relate it to the original EPR paradox. The paper also explores the hierarchy of nonlocal properties, showing that steerability is stronger than nonseparability but weaker than Bell-nonlocality. The authors analyze Werner states and isotropic states to illustrate these hierarchies and derive conditions for steerability in these families. Additionally, they investigate Gaussian states and provide a linear matrix inequality for steerability under Gaussian measurements. The paper concludes with open questions regarding asymmetric states, the utility of steerability in tasks beyond the defining one, and the existence of steering analogs of Bell-operators and entanglement witnesses.