Generation of genuine entanglement up to 51 superconducting qubits

• Published in: Nature (London) Vol. 619; no. 7971; pp. 738 - 742
• Main Authors: Cao, Sirui, Wu, Bujiao, Chen, Fusheng, Gong, Ming, Wu, Yulin, Ye, Yangsen, Zha, Chen, Qian, Haoran, Ying, Chong, Guo, Shaojun, Zhu, Qingling, Huang, He-Liang, Zhao, Youwei, Li, Shaowei, Wang, Shiyu, Yu, Jiale, Fan, Daojin, Wu, Dachao, Su, Hong, Deng, Hui, Rong, Hao, Li, Yuan, Zhang, Kaili, Chung, Tung-Hsun, Liang, Futian, Lin, Jin, Xu, Yu, Sun, Lihua, Guo, Cheng, Li, Na, Huo, Yong-Heng, Peng, Cheng-Zhi, Lu, Chao-Yang, Yuan, Xiao, Zhu, Xiaobo, Pan, Jian-Wei
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 27.07.2023; Nature Publishing Group
• Subjects: 639/766/483/2802; 639/766/483/481; Accuracy; Clusters; Gates; Humanities and Social Sciences; Microprocessors; multidisciplinary; Phase transitions; Quantum computing; Quantum entanglement; Quantum mechanics; Quantum theory; Qubits (quantum computing); Science; Science (multidisciplinary); Superconductivity
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/s41586-023-06195-1

Scalable generation of genuine multipartite entanglement with an increasing number of qubits is important for both fundamental interest and practical use in quantum-information technologies 1 , 2 . On the one hand, multipartite entanglement shows a strong contradiction between the prediction of quantum mechanics and local realization and can be used for the study of quantum-to-classical transition 3 , 4 . On the other hand, realizing large-scale entanglement is a benchmark for the quality and controllability of the quantum system and is essential for realizing universal quantum computing 5 – 8 . However, scalable generation of genuine multipartite entanglement on a state-of-the-art quantum device can be challenging, requiring accurate quantum gates and efficient verification protocols. Here we show a scalable approach for preparing and verifying intermediate-scale genuine entanglement on a 66-qubit superconducting quantum processor. We used high-fidelity parallel quantum gates and optimized the fidelitites of parallel single- and two-qubit gates to be 99.91% and 99.05%, respectively. With efficient randomized fidelity estimation 9 , we realized 51-qubit one-dimensional and 30-qubit two-dimensional cluster states and achieved fidelities of 0.637 ± 0.030 and 0.671 ± 0.006, respectively. On the basis of high-fidelity cluster states, we further show a proof-of-principle realization of measurement-based variational quantum eigensolver 10 for perturbed planar codes. Our work provides a feasible approach for preparing and verifying entanglement with a few hundred qubits, enabling medium-scale quantum computing with superconducting quantum systems. A scalable approach is provided for preparing and verifying intermediate-scale genuine entanglement on a 66-qubit superconducting quantum processor.