Wiseman H M, Jones S J, Doherty A C
Centre for Quantum Computer Technology, Centre for Quantum Dynamics, Griffith University, Brisbane 4111 Australia.
Phys Rev Lett. 2007 Apr 6;98(14):140402. doi: 10.1103/PhysRevLett.98.140402.
The concept of steering was introduced by Schrödinger in 1935 as a generalization of the Einstein-Podolsky-Rosen paradox for arbitrary pure bipartite entangled states and arbitrary measurements by one party. Until now, it has never been rigorously defined, so it has not been known (for example) what mixed states are steerable (that is, can be used to exhibit steering). We provide an operational definition, from which we prove (by considering Werner states and isotropic states) that steerable states are a strict subset of the entangled states, and a strict superset of the states that can exhibit Bell nonlocality. For arbitrary bipartite Gaussian states we derive a linear matrix inequality that decides the question of steerability via Gaussian measurements, and we relate this to the original Einstein-Podolsky-Rosen paradox.
1935年，薛定谔引入了引导（steering）的概念，将爱因斯坦-波多尔斯基-罗森佯谬推广到任意纯二分纠缠态和一方的任意测量情况。直到现在，它从未得到过严格定义，所以（例如）还不清楚哪些混合态是可引导的（即可用于展示引导现象）。我们给出了一个操作性定义，并据此证明（通过考虑韦尔纳态和各向同性态），可引导态是纠缠态的一个严格子集，且是能展现贝尔非定域性的态的一个严格超集。对于任意二分高斯态，我们推导了一个线性矩阵不等式，该不等式通过高斯测量来判定可引导性问题，并将其与原始的爱因斯坦-波多尔斯基-罗森佯谬联系起来。
