Quantum computing, the charm of interdisciplinary
Quantum computing and quantum information have undergone tremendous and profound changes over the past two decades in the deep integration of theoretical computer science. Today, quantum technology is no longer a branch of physics, but a comprehensive discipline: its further development requires the cooperation of people with different backgrounds in physics, computing, mathematics, and engineering.
Different from international research institutions, at present, most of the domestic researchers in this industry have a physical background, while very few computer researchers are engaged in quantum computing theory. Associate Professor Yao Penghui from the Department of Computer Science and Technology of Nanjing University has focused on this field. Professor Yao started with computational complexity, quantum algorithms and quantum information theory, and has now made a series of important achievements in algorithm and communication complexity.
In 2021, Yao Penghui's research group's paper "Sharing a non-local quantum game with the most noisy entangled state is decidable" was written and released: a special kind of non-local game is considered, allowing players to share an infinite number of copies of the most noisy maximum. entangled state. It is shown that such games are decidable and that there exists an algorithm that approximates to arbitrarily small precision. Combined with the recent groundbreaking work MIP*=RE by Ji, Natarajan, Vidick, Wright, and Yuen, this result implies that nonlocal games are not robust to the noise of shared entangled states. This proof structure builds on and generalizes a decidable framework for non-interactive simulations of joint distributions; develops a series of new techniques for Fourier analysis of matrix spaces and proves the The principle of quantum invariance and the hypercompression inequality. This achievement has been shared in academic conferences such as AMSS-UTS Quantum Computing Joint Symposium, (Jinan) Algorithm and Computation Theory Symposium and other academic conferences, and was subsequently accepted by SIAM Journal of Computing and will be published soon. This novel research will have many potential applications in quantum information theory, quantum complexity theory.
Recently, Photon Box had the honor to contact and interview Associate Professor Yao Penghui of "Quantum Computing: An Application Method".
Full text of the interview
1. Briefly talk about your study and work experience?
My undergraduate degree is East China Normal University, majoring in mathematics. Later, he studied for a master's degree at the Chinese Academy of Sciences, and then a doctorate at the National University of Singapore's Center for Quantum Technology. After graduating from a doctorate, he worked as a postdoctoral fellow at the National Mathematics Center of the Netherlands, the Institute of Quantum Computing at the University of Waterloo in Canada, and the Joint Center for Quantum Information and Computer Science at the University of Maryland in the United States. Research, returned to China in 2018 and joined Nanjing University.
2. Has the research direction and research content changed in these experiences?
There are some changes. During the Ph.D. period, I mainly cooperated with my supervisor. At first, I mainly worked on classical computing theory, and then slowly turned to quantum. When I arrived in Canada, I basically devoted myself to quantum computing. Before returning to China, I did computer-related work; Collaborate on experiments and do some physics too.
3. Can you briefly introduce the recent developments?
There are now five doctoral students in the group, only one year is senior, and there are several masters and undergraduates. So most of the energy is to take students to do projects. Our research is all related to quantum computing. Now I bring students to cooperate with some physics and mathematics research groups, as well as some foreign friends. Hope to expand the knowledge and knowledge of the students in the next group.
4. Why did you choose to join Nanjing University in the first place, and what kind of support does the school provide?
The Department of Computer Science at NTU has a tradition of doing theoretical computer science, and the department is very supportive of this direction. Theoretical computer science is a bit special. It is more inclined to mathematics, and the articles are published slowly, so a more tolerant environment is needed to allow us to calm down and do it.
5. Does the team carry out domestic and foreign cooperation? Has the previous unhappiness with IBM affected your international cooperation?
We are still cooperating with Tsinghua University, University of Southern California, Harvard and some universities. The IBM collaborator is actually my junior and apprentice in the Netherlands, and I have a good personal relationship. Now I still have some collaborations with him, and we recently published another paper together. However, it is currently limited to cooperation on some topics in non-quantum computing.
6. Have you achieved some research results together with students?
Yes, I did a quantum computing theory result with my first PhD student
(https://arxiv.org/abs/2108.09140). At present, there is only a preprint online, and the article has been accepted by the SIAM Journal of Computing, an authoritative journal of theoretical computer science, but it may take a while to line up for the publication. This is a particularly rewarding job for me. This is the first time I have conducted research with students, and the research questions and tools used are very different from my previous research topics. I think it's amazing how it ended up being done.
There are also some results of quantum distributed algorithms published. Now several students in the group have also made some results, some are already submitting, and some are still writing papers.
7. Is the team currently mainly researching quantum algorithms on classical computers? Does Nanjing University have quantum computers?
My team is now mainly studying the computing power of quantum computers. Specifically, if there is a large-scale quantum computer now, what can you do with it and what can't it do. This is a purely theoretical question. A little closer to reality is what small-scale quantum computers in the lab can and cannot do. The study of what it can do is mainly to see what advantages it will have; the study of what it cannot do is mainly from the perspective of cryptography and security, hoping to construct some schemes that quantum computers cannot crack encryption.
As far as I know, some research teams in the Department of Physics of our school already have small quantum computers, but I don't know how many qubits they can make. There are teams in our school's modern engineering and technology department that have optical platforms on which small-scale quantum algorithms can be implemented.
8. Does the team currently encounter any bottlenecks or problems in scientific research?
There is no particularly noticeable bottleneck. Maybe it's because I do theoretical research and don't involve building a laboratory, so I feel pretty smooth; I had some difficulties before because when I first became a teacher, I didn't have experience with students, and I didn't know how to design some suitable topics for students. , I will give students some problems that I have been thinking about for many years, and now I am slowly groping for some experience.
9. Referring to your early years of study and work experience in Singapore, Canada, the United States and other countries, do you have any personal experience of quantum technology research in different countries?
I feel that foreign countries are more in-depth in promoting the intersection of disciplines. For example, I mainly stayed in the Quantum Research Center before. There were physics, computer, mathematics, and engineering researchers in the same building. I listened to reports and ate together with these people every day. There are various academic reports. Today, there may be one A very mathematical report. Tomorrow one will talk about how to make an atomic clock. In this environment, everyone has learned about different disciplines, and interdisciplinary cooperation will naturally occur.
10. Do you feel that the development of quantum technology abroad will be more comprehensive and comprehensive than China's? Or is China still lacking in the development of quantum technology?
Indeed, the development of foreign quantum technology is more comprehensive, and there are many people with different professional backgrounds. For example, at the QuICS Center at the University of Maryland, more than half of the teachers and students have computer backgrounds. Then the floor downstairs of their center is a joint quantum research institute JQI, which is basically filled with physics background. This makes it very easy for them to work together. Like the Canadian Institute of Quantum Computing IQC, Singapore's quantum technology center CQT is basically this model.
11. Some Western countries (such as the United States) are mainly driven by technology companies for the development of quantum information technology, while China is driven by academic institutions. How to view this difference?
I don't think the main drivers of quantum information technology in the US are tech companies. I think it is also where academia and industry are starting to go hand in hand. For example, the NSF, the Department of Energy, and the Department of Defense in the United States have invested a lot of money in American colleges and universities in recent years, and designated these colleges to recruit quantum teachers, but they will not pay if they cannot recruit them. It's just that these news are only more concerned by the academic community, and the outside world knows less.
However, the quantum computing research of the top companies in the United States is also very powerful, such as IBM, Google, and Microsoft. They are also good at news, so it feels like these big companies are pushing quantum computing research.
12. Combined with the development status at home and abroad, what application scenarios do you think quantum technology will have in the future?
Now the academic community is paying more attention. At present, if the scale of quantum computers is slightly larger, they can be used to simulate some quantum systems that cannot be simulated by classical computers, which hopefully can be used to solve some small-molecule drug design problems. Then quantum computers can exponentially accelerate some numerical computing problems, which can be applied to some large-scale computing problems, such as weather forecasting and so on. In terms of quantum cryptography, everyone is already studying how to secure a cryptographic system for quantum computers, and now there is a special branch of cryptography called post-quantum cryptography that is studying this.
I think many applications of quantum technology in the short term are not directly visible to everyone. For example, it makes some problems faster and safer. I am more interested in how to use quantum computers to help solve some computational problems in chemistry. Of course, this may not be felt by everyone.
I mainly focus on the quantum algorithms of the quantum systems of some special Hamiltonian systems, whether they can be solved efficiently. These special Hamiltonian systems have specific chemical structures, which may be more technical.
Recently, I have been working with a colleague of mine and a team from the University of Hong Kong, focusing on some quantum measurement and machine learning. Quantum measurement is mainly done by people majoring in physics, and machine learning is mainly done by computer people. We found that many of the problems studied in these two directions are actually very similar. We mainly see whether the methods of machine learning can be applied to quantum measurement.
13. What do you think of the "quantum hype" phenomenon that exists?
I think this is hard to avoid when one direction fires up. After Google and Microsoft began to invest in quantum technology on a large scale around 2014 and 2015, it was obvious that there was more and more news in this regard. Then, as soon as these news spread, some of them became more and more mysterious. As long as quantum technology continues to advance, everyone will gradually see that this discipline is making rapid progress.
14. Now countries around the world are vigorously publicizing and issuing government announcements to invest billions in quantum technology. What do you think of this phenomenon? Or why invest billions in the development of quantum technology?
Quantum technology includes not only quantum computing, but also quantum sensing, quantum communication, and more. I borrowed a point of view I heard before. At present, it is the second quantum revolution. The first quantum revolution made us realize that the microscopic world is described by quantum mechanics. At that time, we could only passively use quantum mechanics to explain some phenomena. Now in the second quantum revolution we are actively using quantum mechanics to design something we need.
So I think that promoting the development of quantum technology is not just about making quantum computers, but the development of its related processes and technologies has a great role in all aspects.
15. More and more scientists are participating in or creating commercial companies. Do you have any plans for this?
Currently no, I still prefer the environment in college.
16. What do you hope to achieve in your research career?
There are many areas in quantum computing that are still blank, and there are many unsolved problems. I hope to be able to establish a theory in a field and systematically solve a series of problems in it. Of course, it would be even better if this theory could also be realized experimentally.
17. What would you like to say to your readers about your latest translation, Quantum Computing: An Approach to Application?
At present, the textbooks of quantum computing on the market either focus on mathematical theory, or focus on physical principles and experiments. This book is written for practitioners with a computer background. So, if you want to understand quantum computing and commonly used quantum algorithms, especially the implementation of these algorithms, but don't want to get too involved in mathematical proofs, or physical principles, this book is a good choice.
About Yao Penghui
Yao Penghui, associate professor of Nanjing University; graduated from CQT, National University of Singapore with a Ph.D. (QuICS) for postdoctoral research. He has published many papers in top international conferences on theoretical computer science such as STOC, FOCS, and CCC, as well as in IEEE Transaction on Information Theory, a top journal of information theory.
Specific research directions:
1. Quantum computational complexity and quantum information theory
2. Classical and quantum information theory
3. Fourier analysis in theoretical computer science and quantum computing
4. De-randomize
