Authors
Niu, Jingjing; Zhang, Libo; Liu, Yang; Qiu, Jiawei; Huang, Wenhai; Huang, Jiaxiang; Jia, Hao; Liu, Jiawei; Tao, Ziyu; Wei, Weiwei; Zhou, Yuxuan; Zou, Wanjing; Chen, Yuanzhen; Deng, Xiaowei; Deng, Xiuhao; Hu, Changkang; Hu, Ling; Li, Jian; Tan, Dian; Xu, Yuan; Yan, Fei; Yan, Tongxing; Liu, Song; Zhong, Youpeng; Cleland, Andrew; Yu, Dapeng
Abstract
Low-loss superconducting aluminium cables and on-chip impedance transformers can be used to link qubit modules and create superconducting quantum computing networks with high-fidelity intermodule state transfer.Scaling is now a key challenge in superconducting quantum computing. One solution is to build modular systems in which smaller-scale quantum modules are individually constructed and calibrated and then assembled into a larger architecture. This, however, requires the development of suitable interconnects. Here we report low-loss interconnects based on pure aluminium coaxial cables and on-chip impedance transformers featuring quality factors of up to 8.1 x 10(5), which is comparable with the performance of our transmon qubits fabricated on a single-crystal sapphire substrate. We use these interconnects to link five quantum modules with intermodule quantum state transfer and Bell state fidelities of up to 99%. To benchmark the overall performance of the processor, we create maximally entangled, multiqubit Greenberger-Horne-Zeilinger states. The generated intermodule four-qubit Greenberger-Horne-Zeilinger state exhibits 92.0% fidelity. We also entangle up to 12 qubits in a Greenberger-Horne-Zeilinger state with 55.8 +/- 1.8% fidelity, which is above the genuine multipartite entanglement threshold of 1/2.