Centre for Quantum Dynamics and Centre for Quantum Computation and Communication Technology, Griffith University, Brisbane, Queensland 4111, Australia.
Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, U.K.
Sci Adv. 2017 Apr 28;3(4):e1602743. doi: 10.1126/sciadv.1602743. eCollection 2017 Apr.
Quantum mechanics admits correlations that cannot be explained by local realistic models. The most studied models are the standard local hidden variable models, which satisfy the well-known Bell inequalities. To date, most works have focused on bipartite entangled systems. We consider correlations between three parties connected via two independent entangled states. We investigate the new type of so-called "bilocal" models, which correspondingly involve two independent hidden variables. These models describe scenarios that naturally arise in quantum networks, where several independent entanglement sources are used. Using photonic qubits, we build such a linear three-node quantum network and demonstrate nonbilocal correlations by violating a Bell-like inequality tailored for bilocal models. Furthermore, we show that the demonstration of nonbilocality is more noise-tolerant than that of standard Bell nonlocality in our three-party quantum network.
量子力学承认一些关联，这些关联无法用局部现实模型来解释。最受研究的模型是标准局部隐变量模型，它们满足著名的贝尔不等式。迄今为止，大多数研究工作都集中在双粒子纠缠系统上。我们考虑了通过两个独立纠缠态连接的三方之间的相关性。我们研究了一种新的所谓“双局域”模型，它相应地涉及两个独立的隐变量。这些模型描述了在量子网络中自然出现的场景，其中使用了几个独立的纠缠源。我们使用光子量子位构建了这样一个线性的三节点量子网络，并通过违反为双局域模型定制的类似于贝尔的不等式来证明非局域相关性。此外，我们还表明，在我们的三方量子网络中，非局域性的证明比标准贝尔非局域性的证明更能耐受噪声。
