Quantum Nonlocality in Any Forked Tree-Shaped Network

• Published in: Entropy
• Main Authors: Lihua Yang, Xiaofei Qi, Jinchuan Hou
• Format: Article
• Language: English
• Published: MDPI AG 2022-05-01
• Subjects: quantum correlation; nonlocality; Bell inequality; quantum network
• Online Access: https://www.mdpi.com/1099-4300/24/5/691

In the last decade, much attention has been focused on examining the nonlocality of various quantum networks, which are fundamental for long-distance quantum communications. In this paper, we consider the nonlocality of any forked tree-shaped network, where each node, respectively, shares arbitrary number of bipartite sources with other nodes in the next “layer”. The Bell-type inequalities for such quantum networks are obtained, which are, respectively, satisfied by all <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mo>(</mo><msub><mi>t</mi><mi>n</mi></msub><mo>−</mo><mn>1</mn><mo>)</mo></mrow></semantics></math></inline-formula>-local correlations and all local correlations, where <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><msub><mi>t</mi><mi>n</mi></msub></semantics></math></inline-formula> denotes the total number of nodes in the network. The maximal quantum violations of these inequalities and the robustness to noise in these networks are also discussed. Our network can be seen as a generalization of some known quantum networks.