The advent of the computer in the 20th century brought an explosion of innovation, productivity and economic development. But so-called “classical computers” are limited by their physical properties, and have seen a relative deceleration in technological progress in recent years. However, a new generation of computers leveraging phenomena from quantum physics promises exponentially greater power that, at least in certain areas, can enable a new era of transformative innovation. In this edition of From the Future, three Notre Dame researchers give their perspectives on the powers and applications of quantum computers, describe the cutting-edge research they are conducting and consider the future of quantum computing here on campus.
Quantum programming for computers and humans
Zhiding Liang, PhD student, Department of Computer Science and Engineering
Courtesy of Zhiding Liang
Zhiding Liang, PhD student in computer science and engineering, did his undergraduate studies in electrical engineering and is trained in the world of classical devices and circuits.However, in pursuing graduate education, Liang decided to take a leap into quantum computing, a field he thinks has “great potential.”Liang explained that the potential of quantum computing lies in the basic processing unit for these systems: the quantum bit, or the “qubit.” Classical binary computer transistors can only be in one of two states, zero or one, representing “off” or “on” switches for electrical signals. Leveraging quantum properties, qubits can represent zero or one, or any proportion of zero and one at the same time — a phenomenon called “superposition.”Superposition enables quantum computers to wield immense computational power since the amount of information a system can process grows exponentially with each additional qubit.However, quantum computers have limitations. In terms of hardware, qubits are incredibly fragile devices. To maintain a state of superposition, qubits require particular environmental conditions (temperature, noise, etc.). If such conditions are not maintained, qubits could experience “decoherence,” or losing their power of superposition, and, in effect, devolving into classical binary bits.Liang focuses on solving problems on the software side of things. His research looks at ways to optimize quantum computer architecture to improve the performance of algorithms. The difficulty of maintaining superposition and avoiding decoherence often limits the time in which quantum computation is possible. So, decreasing the latency of these systems (the time it takes to send data) is important for making quantum computers usable.When he isn’t programming quantum computers, Liang works on a different kind of programming: educational lectures about quantum computing for fellow students.As an electrical engineer, Liang came to quantum computing without background knowledge in physics, which is necessary even for software-focused researchers like himself.Liang said that his first semester as a PhD student involved extensive studies outside of class to get up to speed on fundamental physics concepts. This was frustrating due to the lack of resources online and even from other universities.Liang was inspired to create the Quantum Computer System Lecture Series to make the transition to quantum computing easier for students like himself who do not have a physics background.“I think there’s not enough open source resources online,” Liang said. “I hope to offer a platform to let students who are interested in quantum computing have a pathway to get in touch with this area.”The lecture series has featured 33 talks from quantum computing students and researchers from around the world. Topics range from introductions to basic quantum concepts to state-of-the art research outcomes.Liang hopes that his lecture series will spark interest in quantum computing at Notre Dame. He recognizes that this field can be intimidating due to the high knowledge bar and uncertainty about when this technology will arrive. But he is optimistic about quantum computers and the opportunities for Notre Dame and its students.“I want to contribute to building a quantum computing community at Notre Dame,” Liang said. “Quantum computing is still a really young area. There’s lots of things you can do … there’s a lot of opportunities.”
Getting “quantum ready” in Silicon Valley
Mariya Vyushkova, Quantum Computing Research Specialist at the Notre Dame Center for Research Computing, Visiting Scientist at IBM Research
Courtesy of Mariya Vyushkova
While the quantum community in South Bend is still in its infancy, members of the Notre Dame community are forming connections with some of the world’s premier hubs for quantum computing research.Dr. Mariya Vyushkova is a quantum computing research specialist with the Notre Dame Center for Research Computing, but she is currently a visiting scientist at IBM Research in San Jose, California studying applications for quantum computing.Vyushkova’s research focuses on the possibilities of using quantum computers for simulations in spin chemistry, a field at the intersection of chemistry and physics that deals with magnetic and spin effects in chemical reactions.Spin chemistry is closely connected to the development of quantum computers. One type of qubit (called the “spin qubit”) uses spin chemistry phenomena to create quantum properties like superposition and enable powerful computation.However, spin chemistry simulations have other practical applications, like studying the manipulation of reactions in biological systems, solar energy technology or organic semiconductors. Overall, Vyushkova said many experts believe that chemistry is the field where quantum computing has the most promising applications and will make the most immediate impact.In discussing future applications for quantum computing, Vyushkova made a point to clarify a common misconception that quantum computers will replace classical computers.This is not the case. Even when quantum computers reach their full potential, they will only have an advantage over classical computers for certain applications. And at the moment, for reasons of unreliability and fragility discussed above, quantum computers “are no match” for classical computers.However, Vyushkova said that we still need to be “quantum ready:” i.e., prepared for the day when quantum computers become reliable enough to be used for their unique advantages.“We cannot just sit here and wait for 10 years for the engineers to build an ideal quantum computer,” Vyushkova said. “We need to learn to use those devices right now.”Vyushkova compared the current state of quantum computers to that of classical computers in the mid-20th century. At that time, computers were huge, slow, noisy, expensive and generally impractical machines. However, early computer scientists were still able to develop techniques and applications so that when the technology became cheaper, faster and more viable, we as a society could leverage computers to the fullest.“It’s possible quantum computers would provide a similar advantage [as classical computers have],” Vyushkova said. “They will never replace classical computers, but in certain fields they are capable of potentially solving problems which are exponentially harder, just unimaginable.”Vyushkova noted that countries like China and Russia are investing significant resources into quantum computing with the belief that this technology will give them a strategic advantage in the future. In this sense, the relatively lower investment into quantum computing in the United States could have serious consequences.“We are at the very beginning; this field is still in its infancy,” Vyushkova said. “If you miss this opportunity, then you won’t be competitive in the future.”
Building a center for quantum innovation
Laszlo Forro, Aurora and Thomas Marquez Professor of Physics of Complex Quantum Matter, Director of Stavropoulos Center for Complex Quantum Matter
Courtesy of Laszlo Forro
Back on Notre Dame’s campus, a new research center aims to provide the physical hardware needed to facilitate the opportunities and applications discussed above.Located on the fourth floor of the Nieuwland Hall of Science, the Stavropoulos Center for Complex Quantum Matter was established in 2019 as a home for research on new materials for next-generation technologies like quantum computing.Dr. Laszlo Forro came to Notre Dame from Switzerland in July 2021 to serve as a professor of physics and director of the Stavropoulos Center, bringing a mindset of doing research that leads to practical applications … at least eventually.“In this branch of condensed matter physics, the goal is always to do something useful,” Forro said. “But I believe that every serious research, sooner or later, will be applied. It’s just a question of different timescales — could be applied in two years, five years or 50.”Quantum computing is one key area of research for the Stavropoulos Center. According to Forro, an important unaddressed issue with quantum computers is longevity: being able to sustain quantum states (i.e., avoid decoherence) long enough to operate the computer and process information.New quantum materials can help solve this issue. Researchers at the Stavropoulos Center are experimenting with different atomic structures and creating pure materials that can extend the lifetime of quantum states, and therefore improve the usability of quantum. computers.
Located on the fourth floor of the Nieuwland Hall of Science, the Stavropoulos Center for Complex Quantum Matter researches, among other things, novel materials for quantum computing.
As noted, quantum computers can’t do everything better or faster than a classical computer. However, once quantum materials are improved, Forro sees a multitude of applications for quantum technology. Potential uses include cryptography in banking or data transferring, drug discovery and AI or machine learning research.Forro also thinks that quantum computing could be a commercially available technology. He suggested that, in the future, we could have USB stick devices that plug into classical computers and enable quantum computation.However, Forro said that these applications are far off, and there is significant uncertainty about timelines for viable quantum computers. For now, Forró’s immediate goals are to expand his team, grow the Stavropoulos center and produce research.“We have hired high-level scientists, and I hope that, based on our performance, we can ask the school to give us a few more positions to extend our research profile and to be more productive,” Forro said.Forro believes that Notre Dame has his back in this effort to build the Stavropoulos Center into a world-class quantum research facility.“If it runs well, I have no doubt that the school will support us to extend the number of [project leaders],” Forro said. “I have a strategic plan and vision for the center, which is supported by the college of science Dean [Santiago Schnell] and also by the Provost [John McGreevy] today. This is a very nice feeling for me as a director — that I will have the full support of the school.”