Generation and robustness of quantum entanglement in spin graphs

• Published in: Quantum information processing Vol. 20; no. 1
• Main Authors: Riegelmeyer, Jan, Wignall, Dan, Estarellas, Marta P., D’Amico, Irene, Spiller, Timothy P.
• Format: Journal Article
• Language: English
• Published: New York Springer US 2021; Springer Nature B.V
• Subjects: Accuracy; Chains; Coupling; Data processing; Data Structures and Information Theory; Entangled states; Graph theory; Graphs; Mathematical Physics; Physics; Physics and Astronomy; Quantum Computing; Quantum entanglement; Quantum Information Technology; Quantum mechanics; Quantum phenomena; Quantum Physics; Spintronics; Quantum computation; Spin graphs; Quantum information; Quantum entanglement; Quantum networks; Partition graphs
• ISSN: 1570-0755; 1573-1332
• DOI: 10.1007/s11128-020-02943-8

Entanglement is a crucial resource for quantum information processing, and so protocols to generate high-fidelity entangled states on various hardware platforms are in demand. While spin chains have been extensively studied to generate entanglement, graph structures also have such potential; however, only a few classes of graphs have been explored for this specific task. In this paper, we apply a particular coupling scheme involving two different coupling strengths to a graph of two interconnected 3 × 3 square graphs such that it effectively contains three defects. We show how this structure allows generation of a Bell state whose fidelity depends on the chosen coupling ratio. We apply partitioned graph theory in order to reduce the dimension of the graph and show that, using a reduced graph or a reduced chain, we can still simulate the same protocol with identical dynamics. Finally, we investigate how fabrication errors affect the entanglement generation protocol and how the different equivalent structures are affected, finding that for some specific coupling ratios they are extremely robust.