The research team composed of Pan Jianwei, Lu Chaoyang, Liu Naile and other research teams from the Institute of Quantum Information and Quantum Science and Technology Innovation of the Chinese Academy of Sciences of the University of Science and Technology of China cooperated with the Shanghai Institute of Microsystems of the Chinese Academy of Sciences and the National Parallel Computer Engineering Technology Research Center to develop the theoretical and experimental methods of stimulated amplification of quantum light sources, constructed the prototype "Jiuzhang 2" with 113 photons and 144 modes, and realized the phase programmable function, completing the rapid solution of the Gaussian Boson sampling task used to demonstrate the "superiority of quantum computing".
According to the now-published theory of optimal classical algorithms, The Nine Chapters II processes Gaussian Bose sampling 1024 times faster than the fastest supercomputers available.
This achievement once again refreshes the international technical level of optical quantum manipulation and further provides experimental evidence for quantum computing acceleration.
The paper was published in the form of "Editor's Recommendation" on October 26, 2021 in the internationally renowned academic journal Physical Review Letters. Barry Sanders, a renowned quantum physicist and professor at Calgary University in Canada, was also invited to transcribe a lengthy review on the Physics website, praising the work as a "dramatictour de force..... An impressive advance over the state-of-the-art.
Figure 1: Overall installation of Chapter 9 No. 2 (Draft: Lu Chaoyang, Peng Lichao)
In principle, quantum computers can obtain more computing power than classical computers in terms of some problems of great social and economic value through specific algorithms. As early as 1981, Feynman came up with the initial idea of quantum computing. The physical implementation of large-scale quantum computers is one of the major challenges at the forefront of science and technology in the world. For the development of fault-tolerant general-purpose quantum computing, because of its harsh fault-tolerant threshold and large-scale number of qubits, there is still a big gap from the current level of human scientific and technological development.
Therefore, to achieve the physical implementation of quantum computing, the international academic community has taken a three-step roadmap. Among them, the first milestone, known academically as "quantum computing superiority", means to efficiently solve specific high-complexity mathematical problems that supercomputers cannot solve in a reasonable amount of time by manipulating nearly a hundred physical bits with high precision, experimentally and conclusively prove the idea of quantum computing acceleration proposed by Feynman forty years ago, and challenge the "extended Church-Turing thesis".
Figure 2: Experimental photos of the 144-mode interferometer (partial) of The Nine Chapters II (Photo: Ma Xiaohan, Yang Jianrui, Li Feng, Deng Yuhao)
Photon-based Bose sampling and superconducting bit-based random line sampling are two important protocols for experiments to demonstrate the superiority of quantum computing. Pan Jianwei's team has been at the international leading level in optical quantum information processing. In 2017, the team built the world's first optical quantum computing prototype that surpassed early classical computers. In 2019, the team further developed the world's highest performance single-photon source with deterministic polarization, high purity, high homogeneity and high efficiency, realized Bose sampling of 20 photon input 60 mode interference lines, and the output Hilbert state spatial dimension reached 1014, approximating the "quantum computing superiority".
In 2020, Pan Jianwei's team successfully built the "Nine Chapters" of the 76 photon 100-mode Gaussian Bose sampling quantum computing prototype, the output quantum state space scale reached 1030, the speed of processing Gaussian Bose sampling was one hundred billion times faster than that of the supercomputer, and at the same time overcoming the loophole that quantum superiority depended on the sample size in Google's random line sampling experiment based on the "planewood" superconducting processor. After the completion of the "Nine Chapters" experiment, Professor Scott Aaronson, who theoretically proposed the Bose sampling algorithm and proved the computational complexity, subsequently received the ACM Prize in Computing from the International Computer Association.
In 2021, the team carried out a series of conceptual and technological innovations based on the "nine chapters". Inspired by the concept of laser-"stimulated radiant light amplification", researchers designed and implemented a stimulated bimodal quantum compression light source, which significantly improved the yield, quality and collection efficiency of the quantum light source. Second, through the compact design of three-dimensional integration and collection of optical paths, the multiphoton quantum interference circuit is increased to 144 dimensions. As a result, the number of photons detected by "Nine Chapters 2" increased to 113, and the spatial dimension of the output state reached 1043. Further, by dynamically adjusting the phase of the compressed light, the researchers achieved a reconfiguration of the Gaussian Bose sampling matrix, demonstrating the programming ability of The Nine Chapters II to solve mathematical problems with different parameters. According to the optimized classical algorithm that has been officially published, the "Nine Chapter Two" processing speed on the problem of Gaussian Bose sampling is hundreds of billions of times faster than that of the fastest supercomputer.
Figure 3: Dissertation data plot. The a plot represents the dimensions of the output state space. The b figure shows the advantage multiple of the optical quantum computing prototype over supercomputing.
The researchers hope that this work will continue to inspire more work on classical algorithm simulations, and that there is room for improvement in the future. Quantum superiority research is not a one-time job, but a competition between faster classical algorithms and ever-improving quantum computing hardware, but in the end quantum parallelism will produce computing power that classical computers cannot match.
The first authors of the paper are doctoral students Zhong Hansen, Deng Yuhao, and Qin Jian. The above projects have been supported by Anhui Province, Shanghai Municipality, the Ministry of Science and Technology, the Chinese Academy of Sciences and the Foundation Committee.
Author: Xu Qimin
Editor: Xu Qimin