# “Nine chapters” win the top position in international quantum computing research

Optical quantum interference physical figure: the lower left is the input optical part, and the lower right is the phase-locked optical path. A total of 100 optical modes are output from the upper part, which are respectively connected with 100 superconducting single-photon detector through low loss single-mode fiber. Photography: Ma Xiaohan, Liang Jing, Deng Yuhao The schematic diagram of the optical system of the “nine chapters” quantum computing prototype machine provided by the University of science and technology of China is as follows: the laser system at the top left generates a peak power femtosecond pulse; the 25 light sources on the left generate 50 channels of single-mode squeezed states through the parameter down conversion process and input them into the 100 mode optical quantum interference network on the right side; finally, 100 high-efficiency superconducting single photon detectors are used to output light to the interferometer Quantum state detection. Chinese scientists have set up a landmark in the fierce competition in Quantum Science and technology frontier. On December 4, the University of science and technology of China announced that its research team composed of Pan Jianwei and Lu Chaoyang cooperated with Shanghai Institute of Microsystems, Chinese Academy of Sciences and National Research Center for parallel computer engineering technology to build a prototype of 76 photons “nine chapters” to solve the mathematical algorithm “Gaussian boson sampling”, which only takes 200 seconds to process 50 million samples The fastest supercomputer in the world will take 600 million years. The related papers were published online in international academic journals on December 4. The reviewers of the magazine commented that this was “a state-of-the-art experiment” and “a major achievement”. Pan Jianwei said that this achievement firmly established China’s position as the first matrix in international quantum computing research. The Gaussian boson sampling algorithm based on “nine chapters” will have important potential applications in the fields of graph theory, machine learning and quantum chemistry in the future. According to pan Jianwei’s team, the reason why the quantum computer was named “nine chapters” is to commemorate the ancient Chinese mathematical monograph. < p > < p > is a mathematical monograph written by Zhang Cang and Geng shouchang in ancient China. Its appearance marks the formation of a complete system of ancient Chinese mathematics and is a historical work with milestone significance. And this new machine named “nine chapters” is also a milestone. < / P > < p > quantum computers have the ability of super fast parallel computing. They can accelerate some important problems exponentially through specific algorithms. The problem of “Gaussian boson sampling” solved in “nine chapters” is one of them. < p > < p > < p > “Gaussian boson sampling” is an algorithm to calculate the probability distribution, which can be used to code and solve a variety of problems. The computational difficulty increases exponentially, and it is easy to exceed the current supercomputer computing capacity, which is suitable for quantum computers to explore solutions. < p > < p > in this study, the 76 photon quantum computing prototype “nine chapters” constructed by Pan Jianwei’s team realized the fast solution of the “Gaussian boson sampling” task. How strong is the computational power of the “nine chapters”? Running at room temperature, it takes only 200 seconds for “nine chapters” to process 50 million samples, and 600 million years for supercomputers to process 50 million samples; it takes only 10 hours for “nine chapters” to process 10 billion samples, and 120 billion years for supercomputers to process 10 billion samples. < / P > < p > “in one minute, nine chapters completed the task that the classic supercomputer could only complete in 100 million years.” Lu Chaoyang, a professor at the University of science and technology of China, one of the co authors of the study, said. < / P > < p > in order to verify whether the calculation of “nine chapters” is accurate or not, pan Jianwei’s team used supercomputing for synchronous verification. “When there are 10 or 20 photons, the results are all right. When it comes to 40 photons, the supercomputing becomes more difficult. However, in Chapter 9, 76 photons are counted.” Lu Chaoyang told reporters. Dirk englen, associate professor of MIT and winner of the Presidential Award and Sloan Award for young scientists, commented that Pan Jianwei’s research “is an epoch-making achievement” and “a milestone in the development of medium-sized quantum computers”. Philip volzer, a professor at the University of Vienna and a member of the American Physical Society, also said: “in their experiments, they have obtained the calculation results that can only be given by the most powerful classical computer in a trillion years, which provides a strong proof of the super power of quantum computers.” In October 2019, the Google team led by American physicist John & middot; martinis announced the development of a 53 qubit computer “Platanus”. “Suzuki” completed 1 million random line sampling tasks in 200 seconds, while the world’s fastest supercomputer “peak” took two days. American scientists have been able to realize “quantum computing superiority” for the first time in the world. < / P > < p > the so-called “superiority of quantum computing”, also known as “quantum hegemony”, this scientific term refers to: as a new thing, once the computing power of quantum computer exceeds the strongest traditional computer on a certain problem, it proves the superiority of quantum computer and makes it cross the threshold of surpassing traditional computer in many aspects in the future. < / P > < p > in fact, at the same time that Google announced “sycamore”, pan Jianwei’s team has realized the “Bose sampling” of 20 photon input 60 mode interference circuit, and the output complexity is equivalent to 48 qubits of Hilbert state space, approaching the “superiority of quantum computing”. < / P > < p > recently, through independent innovation in the fields of quantum light source, quantum interference, single photon detector, etc., the team has successfully constructed the “nine chapters” prototype of “Gaussian Bose sampling” with 76 photons and 100 modes. At the same time, “nine chapters” has a quantum light source with high efficiency, high homogeneity, extremely high brightness and large-scale expansion ability, and 100 mode interference circuit with phase stability, fully connected random matrix, wave packet coincidence degree better than 99.5%, and pass rate better than 98%. It has a lock-in accuracy within the negative 9th power of the relative optical path 10, and a high-efficiency 100 channel superconducting nanowire single photon detector. < p > < p > experiments show that the computing speed of the classical mathematical algorithm “Gaussian boson sampling” is 100 trillion times faster than the world’s fastest supercomputing “Fuyue”, thus realizing the “quantum computing superiority” for the second time in the world. According to Lu Chaoyang, compared with “Platanus”, Jiuzhang has three advantages: first, it is faster. Although it is not the same mathematical problem, compared with the fastest supercomputing equivalent, “nine chapters” is 10 billion times faster than “Platanus”. Second, environmental adaptability. Because of the superconducting system, “sycamore” must operate at – 273.12 ℃ in the whole process, while the “nine chapters” can operate at room temperature except for the detection part which needs minus 269.12 ℃. The third is to make up for the technical loopholes. “Platanus acerifolia” is faster than supercomputing only in the case of small samples, while “nine chapters” is faster than supercomputing in both small and large samples. “For example, Google’s machine sprint can outperform the supercomputing, but long-distance running can’t win; our machine sprint and long-distance running can both win.” < / P > < p > “this work is really important.” Anton & middot; Salinger, President of the Austrian Academy of Sciences and Wolff prize winner and academician of the American Academy of Sciences, said: “quantum computing is being developed around the world to demonstrate the capabilities of beyond conventional computers. Pan and his colleagues have shown that photon based quantum computers can also achieve “quantum computing superiority.” “It’s really an amazing moment for the booming field of quantum computing,” said mitt atatur, a professor at Cambridge University and winner of the Thomas Young Medal of the British physical society. This achievement of Professor Lu and Professor Pan puts photons and photon based quantum technology in the center of the world stage. ” Does the birth of the “nine chapters” quantum computing prototype mean that China has won the “quantum hegemony”? Is mankind about to enter the era of quantum computing? What can we do with it? < / P > < p > for the research of quantum computer, the international peers in this field have recognized that there are three development stages: the first stage is to develop a high-precision special quantum computer with 50 to 100 qubits, which can effectively solve some high-complexity specific problems that supercomputers can’t solve, and realize the milestone of quantum computing superiority in computing science; second, the development of high-precision special-purpose quantum computers with 50-100 qubits The third stage is to develop a quantum simulator that can manipulate hundreds of qubits coherently to solve the problems of great practical value that some supercomputers are not competent for; the third stage is to greatly increase the number of integrated quantum bits to the order of millions, realize fault-tolerant quantum logic gates, and develop a general-purpose programmable quantum computing prototype. Pan Jianwei’s team revealed that although the computational power of “nine chapters” is amazing, it only sets up a milestone in the first stage of quantum computing, and there is still a long way to go. < p > < p > in the era of exponential growth of people’s demand for computing power, quantum computer has become the frontier of the world. Recently, the United States announced the latest plan in the field of quantum computing, and the United Kingdom, the European Union, Japan and other countries have also made corresponding plans. The successful development of the “nine chapters” in China has not only made a milestone progress in “the superiority of quantum computing”, but also provided a potential prospect for the second step to solve some problems of great practical value that supercomputers are not competent for. < p > < p > at present, whether Google’s “plane tree” deals with “random line sampling” or “nine chapters” solves “Gaussian Bose sampling”, they can only be used to solve a specific problem. Pan Jianwei explained that this is because the materials available for building quantum computers are limited, so they can only “cook on food”. Future breakthroughs in quantum computers are more likely to rely on the innovation of new materials in quantum computing hardware. “It’s not a one-off effort, it’s a competition between faster classical algorithms and ever-increasing quantum computing hardware.” Pan Jianwei said. Pan Jianwei revealed that on the basis of the “nine chapters” quantum computing prototype, they will strive to develop a programmable universal quantum computing prototype as soon as possible through a series of technical breakthroughs such as improving the manipulation accuracy of quantum bits. “We hope that through 15 to 20 years’ efforts, we can develop a universal quantum computer, which can be used to solve some widely used problems, such as cryptanalysis, weather forecast, drug design, and so on, and can also be used to further explore some complex problems in the field of physics, chemistry and biology.” < p > < p > in Hefei, Anhui Province, the newly developed quantum computing prototype “nine chapters” occupies almost half of the laboratory and contains thousands of components. This is Pan Jianwei’s team after more than 20 years of research and development. More than 20 years ago, pan Jianwei, the birthplace of quantum mechanics in Austria, met his mentor Salinger at Innsbruck University. Professor Salinger is sitting in a chair with a Nobel laureate behind him