Schematic diagram of the Zuchongzhi-3 chip. 105 qubits and 182 couplers are integrated on the same chip to perform quantum random circuit sampling tasks. (Image from USTC)
Zuchongzhi-3, a superconducting quantum computing prototype with 105 qubits and 182 couplers, has made significant advancements in random quantum circuit sampling. This prototype was successfully developed by a research team from the University of Science and Technology of China (USTC), including Pan Jianwei, Zhu Xiaobo, and Peng Chengzhi, in collaboration with Shanghai Research Center for Quantum Sciences, Henan Key Laboratory of Quantum Information and Cryptography, China National Institute of Metrology, Jinan Institute of Quantum Technology, School of Microelectronics at Xidian University, and the Institute of Theoretical Physics under the Chinese Academy of Sciences. This prototype operates at a speed that is 1015 times faster than the fastest supercomputer currently available and one million times faster than the latest results published by Google. This achievement marks a milestone in enhancing the performance of quantum computation, following the success of Zuchongzhi-2. The research finding has been published as the cover article in the international academic journal Physical Review Letters.
Quantum supremacy is the demonstration of a quantum computer capable of performing tasks that are infeasible for classical computers. In 2019, Google's 53-qubit "Sycamore" processor completed a random circuit sampling task in 200 seconds, a task that would have taken approximately 10,000 years to simulate on the world’s fastest supercomputer at the time. However, in 2023, USTC demonstrated more advanced classical algorithms, completing the same task in about 14 seconds using over 1,400 A100 GPUs. With the use of "Frontier" supercomputers equipped with larger memory, the task is expected to be completed in just 1.6 seconds. As a result, Google’s claim of "quantum computational supremacy" at that time was overturned.
Subsequently, using the optimal classical algorithm as the benchmark, the same team of USTC achieved the first rigorously proven quantum supremacy with the "Jiuzhang" photonic quantum computing prototype in 2020. This was followed in 2021 by the achievement of the same task in a superconducting system, achieved with the Zuchongzhi-2 processor. In 2023, the team’s development of the 255-photon "Jiuzhang-3" demonstrated quantum supremacy that surpassed classical supercomputers by 1016 times. In October 2024, Google's 67-qubit superconducting quantum processor, "Sycamore," demonstrated quantum supremacy by outperforming classical supercomputers by nine orders of magnitude.
Building upon the 66-qubit "Zuchongzhi-2," USTC research team significantly enhanced key performance metrics to develop "Zuchongzhi-3," which features 105 qubits and 182 couplers. The quantum processor achieves a coherence time of 72 μs, a parallel single-qubit gate fidelity of 99.90%, a parallel two-qubit gate fidelity of 99.62%, and a parallel readout fidelity of 99.13%. The extended coherence time provides the necessary duration for performing more complex operations and computations. To evaluate its capabilities, the team conducted an 83-qubit, 32-layer random circuit sampling task on the system. Compared to the current optimal classical algorithm, the computational speed surpasses that of the world's most powerful supercomputer by 15 orders of magnitude. Additionally, it outperforms the latest results published by Google in October of last year by 6 orders of magnitude, establishing the strongest quantum computational advantage in the superconducting system to date.
Following the achievement of the strongest "quantum computational advantage" with "Zuchongzhi-3," the team is actively advancing research in quantum error correction, quantum entanglement, quantum simulation, quantum chemistry, and other areas. Researchers adopted a 2D grid qubit architecture, facilitating efficient interconnections among qubits and enhancing data transfer rates. Based on this architecture, the team integrated surface code and is actively researching quantum error correction with a distance-7 surface code. Plans are in place to increase this distance to 9 and 11, paving the way for massive integration and manipulation of quantum bits.
The team’s work holds profound significance and has received widespread acclaim. One journal reviewer described it as "benchmarking a new superconducting quantum computer, which shows state-of-the-art performance," and a "significant upgrade from the previous 66-qubit device (Zuchongzhi-2)." In recognition of the study’s critical importance, at the same time, the Physics Magazine featured a dedicated viewpoint article that provided an in-depth exploration of its innovations and emphasized its broader significance.
Paper link: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.090601
(Written by LIU Danxu, GE Shuyun, Edited by WU Yuyang, USTC News Center)
