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SUSTech researchers made advances in two-qubit quantum gates with superconducting quantum circuit

Yuan XU      2021-01-06

Recently, the Shenzhen Institute for Quantum Science and Engineering (SIQSE) at Southern University of Science and Technology have made significant experimental progress in implementing two-qubit quantum gates with the superconducting quantum circuit. The research team mainly includes Fei Yan, associate researcher of the Institute, Jian Li, associate researcher of the Institute, Yuan Xu, assistant researcher of the Institute, and their cooperator, Xinsheng Tan, researcher of Nanjing University.

They experimentally implement a high-fidelity, high-scalability two-qubit gate scheme for two superconducting qubits by utilizing a tunable coupler in the superconducting quantum circuit. The research results, entitled “High-Fidelity, High-Scalability Two-Qubit Gate Scheme for Superconducting Qubits” (Phys. Rev. Lett. 125, 240503), have been published in the prestigious academic journal Physical Review Letters,  

How to obtain high-quality two-qubit quantum logical gates without sacrificing scalability is the core issue for large-scale quantum information processing. In the superconducting quantum circuit, the use of a tunable coupler combined with a fixed frequency qubit architecture can effectively solve this problem. In this experimental work, the research team proposed and demonstrated a new two-qubit gate control scheme based on this architecture, and experimentally achieved fast (30ns) high-fidelity (0.995) two-qubit quantum gate operation. Compared with the previous two-qubit quantum gate, this scheme is more robust, requires fewer control lines, and has less crosstalk effect. The system calibration procedure is simplified. Therefore, it has obvious advantages in the large-scale quantum system and will open up new ideas for superconducting quantum chip design.

Yuan Xu (assistant researcher of the SIQSE at SUSTech) and Ji Chu (postgraduate of Nanjing University, now a Ph. D candidate at the SIQSE) are the co-first authors of the paper. Fei Yan, Jian Li, Yuan Xu, and Xinsheng Tan are the corresponding authors. Other authors include Jiahao Yuan, Jiawei Qiu, Yuxuan Zhou, Libo Zhang, Yang Yu, Song Liu, and Dapeng Yu. This work was supported by the National Natural Science Foundation of China, Guangdong Provincial Key Laboratory, and Science, Technology and Innovation Commission of Shenzhen Municipality.

Fig. (a) System eigenenergies as a function of the coupler frequency. (b) Randomized benchmarking of the two-qubit Controlled-Z gate with fidelity of 0.995.