论文标题
通过量子状态广播的钟形非局部性的单拷贝激活
Single-copy activation of Bell nonlocality via broadcasting of quantum states
论文作者
论文摘要
贝尔非局部性的激活是指某些纠缠的混合状态在标准铃场中接纳局部隐藏变量模型的现象，但在更奇特的测量场景中揭示了它们的非本地性质。我们提出了这样的方案，涉及将双分量量子状态的单拷贝的局部子系统与多方播放，并使用该方案来研究两Q Qubit同型状态的非本地性质： \ begin {align} \ nonumberρ_α=α\，|φ^+\ rangle \langleφ^+|+（1-α）\ frac {\ mathbb {1}}} {4}。 \ end {align} 我们提出了两个主要结果，考虑到自然允许（i）最通用的无信号相关性，以及（ii）在任何隐藏变量理论级别上最通用的量子相关性。我们表明，在（i）和（ii）的情况下，该州不接受$α> 0.559 $和$α> \ frac {1} {2} $的本地隐藏变量描述，在（i）和（ii）中，这在这两种情况下都提供了国家纠缠的独立于设备的认证。这些界限明显低于使用该州的单个副本的贝尔非局部性和独立于设备的纠缠认证的$ 0.697 $的$ 0.697 $。我们的结果表明，有少量资源可以实现强烈的非古典性例子。
Activation of Bell nonlocality refers to the phenomenon that some entangled mixed states that admit a local hidden variable model in the standard Bell scenario nevertheless reveal their nonlocal nature in more exotic measurement scenarios. We present such a scenario that involves broadcasting the local subsystems of a single-copy of a bipartite quantum state to multiple parties, and use the scenario to study the nonlocal properties of the two-qubit isotropic state: \begin{align} \nonumber ρ_α= α\,|Φ^+ \rangle\langle Φ^+|+(1-α)\frac{\mathbb{1}}{4}. \end{align} We present two main results, considering that Nature allows for (i) the most general no-signalling correlations, and (ii) the most general quantum correlations at the level of any hidden variable theory. We show that the state does not admit a local hidden variable description for $α>0.559$ and $α>\frac{1}{2}$, in cases (i) and (ii) respectively, which in both cases provides a device-independent certification of the entanglement of the state. These bounds are significantly lower than the previously best-known bound of $0.697$ for both Bell nonlocality and device-independent entanglement certification using a single copy of the state. Our results show that strong examples of non-classicality are possible with a small number of resources.
