Département de Physique Appliquée, Université de Genève, CH-1211 Genève, Switzerland.
Institute for Theoretical Physics, ETH Zurich, Wolfgang-Pauli-Str. 27, 8093 Zürich, Switzerland.
Phys Rev Lett. 2019 Oct 4;123(14):140401. doi: 10.1103/PhysRevLett.123.140401.
Quantum networks allow in principle for completely novel forms of quantum correlations. In particular, quantum nonlocality can be demonstrated here without the need of having various input settings, but only by considering the joint statistics of fixed local measurement outputs. However, previous examples of this intriguing phenomenon all appear to stem directly from the usual form of quantum nonlocality, namely via the violation of a standard Bell inequality. Here we present novel examples of "quantum nonlocality without inputs," which we believe represent a new form of quantum nonlocality, genuine to networks. Our simplest examples, for the triangle network, involve both entangled states and joint entangled measurements. A generalization to any odd-cycle network is also presented.
量子网络原则上允许完全新颖的量子相关性形式。特别是，这里可以证明量子非局域性，而无需各种输入设置，仅通过考虑固定本地测量输出的联合统计数据即可。然而，以前这种有趣现象的例子似乎都直接源于通常形式的量子非局域性，即通过违反标准贝尔不等式。在这里，我们提出了“无输入量子非局域性”的新例子，我们相信这代表了一种新的量子非局域性形式，是网络特有的。我们最简单的例子是三角形网络，涉及纠缠态和联合纠缠测量。还提出了对任何奇数环网络的推广。
