Fall 2020 > Cover Story 

Q Matters

Harnessing the Quantum Power in Flux

Over the past 10 years, we have seen people be consumed by the unstoppable hype of quantum and quantum computing, but only a few know that the exploitation of quantum phenomena, which was initiated in the 1950s, is not novel and has existed for 100 years. Quantum science, however, does seem esoteric because of the unsolved mysteries surrounding it. Even Albert EINSTEIN was once skeptical about quantum mechanics, particularly the physical properties of nature at the scale of atomic or subatomic particles or waves, stating that quantum entanglement was “spooky action at a distance.”1

Centuries have gone by and we have moved from mechanical to digital computation. Those who have been taught the basic concepts of quantum physics in high school-level science class may not even realize that we are already in the “second quantum revolution.” Some advances that we have taken for granted, such as global positioning systems, magnetic resonance imaging, semiconductors, transistors, nuclear power, and lasers, are actually the fruits of first-generation quantum-based technological developments.

Many questions remain unanswered though. How soon will we enter the next stage of quantum revolution? What type of new quantum technology will occur? We don’t know the answers, but one thing is for sure, whatever technology emerges may become a game changer with far-reaching impacts in all fields, from artificial intelligence and communications to pharmaceutical development.

The Race is On

Although the research on quantum science is mainly basic, this has recently become an area of worldwide interest with fierce competition. Quantum computing, quantum communications, quantum metrology, and quantum information science are some popular aspects of quantum science for which places such as Europe, the United States, and China have recognized the importance. They have invested strategically and heavily into exploring the potential uses and technical applications of quantum science from the perspectives of the economy, military, and national security. 

The Quantum Manifesto, released by the European Union in 2016, is a declaration that “calls upon Member States and the European Commission to launch an ambitious, long-term, flagship-scale initiative combining education, science, engineering, and entrepreneurship across Europe.”2 One of its goals, which has been extensively endorsed across Europe, is to expand scientific quantum research.

The United States, as one of the top 10 countries leading the race of quantum computing technology, signed the National Quantum Initiative Act into law in 2018 and is rolling out a 10-year plan for advancing quantum information science and technology applications in the country. New initiatives partnered with universities and tech companies will introduce the principles of quantum information science to US students before they enter college. On the other side of the globe, China is also catching up. After launching the world’s first quantum communications satellite in 2016, the China National Laboratory for Quantum Information Sciences was established to strengthen the research on quantum information and metrology. It is difficult to say which country is taking the lead in this “quantum race,” but obviously, no one wants to lag behind.

Quantum-ready vs. Quantum Reality

Throughout the years, scientists have gleaned a better understanding of the untold possibilities of quantum science. While transformative scientific progress has been made, quantum systems have only been successful in a laboratory environment, due to their delicate nature and sensitivity to external interference. Prof. ZENG Bei, Professor of Physics at HKUST, is among those who understand that quantum reality cannot exist until the many scientific and technological challenges of quantum science are overcome. However, she is optimistic and indomitable.

“There have been enormous improvements in the past 20 years, and we may be one algorithm away,” said Zeng, who has devoted her research to the study of quantum information theory (QIT) during the past 20 years. She recalled what Prof. Peter SHOR once said, “There are no real hard problems in the world; we are simply not smart enough.” Shor is the Morss Professor of Applied Mathematics at Massachusetts Institute of Technology (MIT). He is well-known for inventing the Shor’s algorithm, a quantum algorithm that calculates the prime factors of a large number.By breaking many cryptosystems, this algorithm has driven considerable interest in the creation of quantum computers. As one of Shor’s PhD students at MIT, Zeng has been working closely with him on research projects related to quantum computing and QIT. She shared with us the theoretical and scientific developments in quantum science and provided us a glimpse of the challenges facing scientists today.

“There are a few postulates for the theory of quantum mechanics. First, the state of quantum mechanical system is completely specified by the most fundamental concept of quantum mechanics — wave function,” said Zeng. By wave function, Zeng refers to an equation that describes the behavior of particles. She added that the wave function of a system evolves in time according to the Schrödinger equation, which was introduced by Prof. Erwin SCHRÖDINGER, an Austrian physicist famous for a theoretical experiment involving a feline paradox. “It is a complex value, and everything you see is induced from it,” said Zeng.

Together with Professors Max PLANCK and Werner HEISENBERG, Schrödinger is called the father of quantum mechanics. In 1933, he shared a Nobel Prize in Physics with Prof. Paul A. M. DIRAC, an English theoretical physicist, for “the discovery of new productive forms of atomic theory.”4

Zeng indicated another important postulate of the theory of quantum mechanics incorporated by Prof. John VON NEUMANN, one of the greatest mathematicians of the twentieth century, which states that the collapse of a wave function is formulated by measurement and its stimulation.

All these postulates, which were proposed more than 100 years ago, still provide a general framework of quantum mechanics that facilitates connection with real-world physical systems, such as quantum computing.

\\ “There have been enormous improvements in the past 20 years, 

and we may be one algorithm away.”\\

Too Soon to Ditch the Classical Computers

In 1965, Gordon MOORE, the co-founder and chairman emeritus of Intel Corporation, predicted that the number of transistors on an integrated circuit will double approximately every two years, meaning that the processor’s performance will be exponentially stronger. However, some people have recently commented that this famous Moore’s law is no longer applicable, as we fail to produce transistors with smaller sizes and more computing power. In other words, the transistor used in a digital computer is reaching its physical limitations in terms of the processing power. Zeng agreed, “It is true that the Moore’s Law can’t continue forever as the size of transistors is approaching as small as an atom.”

This limitation has led to the development of quantum computing technology, which is regarded as the next frontier in computing and a possible solution to our quest for a larger storage capacity and more substantial computational power when handling considerable data. Quantum computing, which is based on quantum mechanics, was postulated by Prof. Richard FEYNMAN in 1981. Although he once said that “nobody understands quantum mechanics,” Feynman was one of the greatest physicists to conceive the possibility of quantum computers. Along with Professors Sin-Itiro TOMONAGA and Julian SCHWINGER, Feynman won the Nobel Prize in Physics in 1965 for “their fundamental work in quantum electrodynamics, with deep-ploughing consequences for the physics of elementary particles.”5

Unlike classical binary computers, which are limited to either an on or off (i.e., one or zero) status, quantum computers run on quantum bits (or qubits), which are the basic units of quantum information. Qubits hold the probability of both 0 and 1 simultaneously, which enables exotic quantum phenomena that yield power, such as superposition and entanglement. Since 2010, some tech giants such as IBM, Google, and Microsoft have been pushing the boundaries of quantum mechanics to produce various quantum computers to achieve quantum supremacy — i.e., the performance of computational task considered impossible for classical computers — a term coined by Prof. John PRESKILL, Professor of Theoretical Physics at the California Institute of Technology, in 2012. Yet, it is difficult to maintain the quantum states of qubits in superposition, which are free from the decoherence caused by a noisy environment, and to achieve a fault-tolerant status. 

“Google’s 53-qubit quantum computer is a big breakthrough but it can’t simulate. Though we have done something that a classical computer can’t do, the error correction does not work,” said Zeng. Recently, IonQ, a start-up based in the US state of Maryland, claimed that its newly launched 32-qubit quantum computer with “low-gate-error” is the most powerful ever and will soon be available on the market. Part of the scientific community remains cynical and hopes that IonQ will provide more research to back up their claims. Perhaps, it is still too soon to tell whether the quantum computer is a dream or a nightmare, a question asked by two French physicists 24 years ago.6 

In 2017, in an article titled Quantum Computing in the NISQ Era and Beyond, Preskill again proposed a new term called noisy intermediate-scale quantum (NISQ). He explained that “NISQ devices will be useful tools for exploring many-body quantum physics, and may have other useful applications, but the 100-qubit quantum computer will not change the world right away.”7 Many agreed with Preskill that progress on quantum computing is underway, making it possible for researchers and scientists to venture into certain new and short-term applications.

“There have already been increasingly more theoretical discussions on the implications and utilities of imperfect, intermediate-scale quantum computers which are just barely beyond what we could efficiently simulate by nonquantum means. There is a fair chance that such devices will become reality in a few years’ time, and it is an interesting question to ask what they can — and cannot — do when compared to classical computers,” said Prof. Adrian PO Hoi-Chun, a condensed matter theorist who is particularly interested in research on materials science and QIT. He will join HKUST as an Assistant Professor in March 2021.

Quantum Materials for a New Science

Another emerging field of quantum mechanics and computer science is quantum information science (QIS), an evolving interdisciplinary subject that spans multiple topics and covers fundamental areas of science and technology, such as physics, engineering, and computer science. QIS not only concerns the performance of information processing tasks, such as information transmission, but also aims to find methods for building fault-tolerant architectures for quantum computers by harnessing superposition and entanglement. To process and store quantum information under controlled quantum states, a quantum mechanical system that offers suitable materials and devices is required.

In relation to his research, Po indicated that quantum materials, with their exotic physical properties, have been proposed as promising ingredients that can enable the next technological breakthroughs. However, these promises can only be delivered if the desirable properties of the materials can be demonstrated outside stringent conditions, such as labs.

“It is important to expand the pool of quantum materials we know, as well as to identify the practical routes for optimizing the materials such that they can function under much more benign conditions. Part of my research is along this direction, which aims at devising more efficient means to predict candidate quantum materials with the desired properties,” said Po, who wants to develop theories that can explain and even predict material properties in which sextillions of quantum particles, such as electrons, interact strongly with each other. Then, the ultimate goal will be to convert his understanding into technological applications.

Prof. Berthold JÄCK is another scholar who will become the HKUST faculty in early 2021. As an experimental scientist whose research focuses on quantum matter and microscopy, Jäck’s research on quantum materials has two main directions. The first direction includes a fundamental research component on new quantum materials and instrumentation development, which is useful for pushing the frontiers of knowledge on quantum matter and generating an outlook on the type of technology that might emerge out of these discoveries on a longer time scale of approximately twenty years. The second direction addresses more applicable topics, such as the physics of materials for applications in superconducting qubits.

“At Princeton University, before joining HKUST, we made some very promising advances in terms of finding new materials that are better suited for their application in superconducting qubits and developing a better understanding of their intrinsic properties. Right now, we are just at the beginning of this type of research, and a lot of open questions and opportunities remain, including both the optimization of the existing material platforms that are typically based on elemental superconductors and the search for new compounds with, hopefully, much improved properties,” said Jäck.

Jäck’s lab at HKUST will apply advanced microscopy techniques and develop quantum microscopy techniques to explore novel quantum phases of matter. He stated that quantum matter or quantum materials research is a dynamic research area that aims to discover novel materials for which the properties cannot be explained by classical physics.

“These materials can entail novel types of superconductors, which can facilitate energy-efficient electronic devices, and topological materials with the potential to enable spintronic applications, where information is transmitted by tiny magnetic moments across nanoscopic wires. It turns out that many of these fascinating material properties arise from quantum phenomena occurring at very small length scales on the order of atoms, and suitable measurement methodologies will be required to shed light on these microscopic processes,” said Jäck.

By using scanning tunneling microscopy (STM) technology, an incredibly powerful technique to study quantum materials, Jäck and his research team will investigate and visualize various fundamental material properties, such as electronic and magnetic characteristics, with atomic-scale resolution. Jäck explained, “STM is an extremely useful technique to generate microscopic insights on the properties of quantum materials, which cannot be obtained through any other experimental means.”

During his postdoctoral studies in the laboratory of Prof. Ali YAZDANI at Princeton University, Jäck and his team used STM to visualize the existence of a peculiar quantum particle, the so-called Majorana zero mode, on a novel quantum material platform that they developed. Jäck mentioned that this particle can revolutionize the field of quantum computing through its unique properties.

A Myriad of Opportunities

It does not take a rocket scientist to understand Einstein’s famous quote, “In the middle of every difficulty lies opportunity.” The COVID-19 pandemic has had major impacts on every city and every country. Amid this difficult time, how are scientists preparing themselves for future technological developments?

“I think the Coronavirus pandemic has generated fresh momentum for a digitalized presence and future, where more and more businesses and organizations are discovering and adopting its benefits. That entails the adoption of home office programs and online meetings and conferences as well as the integration of cloud storage and sharing plans into the workflow. I can imagine that the integration of quantum technology will complement these developments, and that, for example, quantum cryptography could be incredibly useful to guarantee private communication and data transfer channels between both professional and private actors in this increasingly digitalized world,” said Jäck.

Looking forward, Jäck, as a scientist, understands that several important questions in quantum research regarding the development of quantum technological applications await solutions. He emphasized that these efforts will consume considerable time and money. On another front, as an educator, Jäck said that it is our responsibility to educate the necessary talent in the field of quantum technologies, as these individuals will drive the transformation to a quantum world and build the quantum companies of tomorrow.

Po, who will collaborate with Jäck to carry out research headed by a diverse group of scholars at HKUST, echoed that researchers have been making steady progress toward the goal of converting findings into technological applications. This progress is particularly due to the development of an “entanglement-centric” description of a quantum many-body ground state in the past few decades.

“Facing the experimental and technological challenges of quantum science, I’m optimistic that we are on the right track, and when the current ideas are developed further, we might one day be able to clear the road blocks and stand up to the challenges coming from our colleagues working on the experimental and technological frontiers,” said Po. He added that he looks forward to joining forces with the research groups of other condensed matter theorists at HKUST to better understand and predict the properties of exotic materials.

“There are many strong experimental groups in the HKUST Physics Department who have been making many interesting discoveries in quantum materials. It would be exciting to collaborate with them to see how our perhaps abstract ideas could be realized,” said Po, who added “I would also love to learn more about QIT from Prof. Zeng. I think QIT is like the backbone of all other domains of quantum sciences. It provides the grounds which justify the development of other quantum sciences, and turning it around the other quantum sciences serves as the ports connecting QIT with the real world.”

Zeng, whose research strives to bring us closer to the goal of reliable transmission and processing of quantum information, is trying to narrow the gap between theory and reality. From the theoretical viewpoint, Zeng is seeking to construct a broad theory for building a large class of quantum error-correcting codes. From the practical viewpoint, she is focused on the design of quantum error-correcting codes with properties that are suitable for high-rate quantum information transmission through practical physical channels, and reliable quantum computation with a high noise tolerance and low resource requirement.

Apart from Zeng, scholars from a wide range of fields have been carrying out research on quantum science and technology at HKUST. The Center for Quantum Materials led by Prof. WANG Ning, Chair Professor of Physics, and Prof. Vic LAW Kam-Tuen, Dr. Tai-chin Lo Associate Professor of Science and Associate Professor of Physics, provides a platform for research groups to conduct theoretical and experimental research activities. On the other hand, the research group of Prof. Gyu-Boong JO, Associate Professor of Physics, utilizes atomic quantum simulators and explores the interface between atomic, molecular, and optical physics, as well as condensed matter and quantum information science. Jo also leads the Laboratory for Ultracold Quantum Gases at HKUST. Recently, IAS Senior Fellow Prof. DAI Xi, Chair Professor of Physics, whose research focuses on electronic structure studies of topological and strongly correlated materials, was awarded the 2019 James C. McGroddy Prize for New Materials for “the theoretical prediction, design and realization of non-magnetic and magnetic topological semi-metals and new types of topological insulators.”8

The quantum age may not be around the corner, but with joint efforts from the greatest minds in different fields, our research on quantum science will pay dividends someday.

Prof. ZENG Bei 曾蓓

As a chess master at the age of 14, Zeng’s interest in pursuing a university degree was sparked by the defeat of the then World Chess Champion Garry KASPAROV by IBM’s supercomputer, “Deep Blue,” in a chess match in 1997. Zeng received her Bachelor’s degree in Physics and Mathematics and Master’s degree in Physics from Tsinghua University in 2002 and 2004, respectively. In 2009, She obtained her PhD in Physics from MIT and became a postdoctoral fellow at the Institute for Quantum Computing and the Department of Combinatorics and Optimization, University of Waterloo from 2009 to 2010. In 2010, she joined the Department of Mathematics and Statistics, University of Guelph, as an Assistant Professor and was promoted to the post of Professor in 2018. Zeng is now a Professor of Physics at HKUST, where she focuses on research related to quantum information, quantum computing, and quantum error correction. 

Prof. Berthold JÄCK

After graduating with distinction in Nanoscience from Würzburg University, Germany, Jäck obtained his PhD in Physics from the École Polytechnique Fédérale de Lausanne, Switzerland in 2015. He joined the Physics Department at Princeton University as a Postdoctoral Research Fellow of the Alexander-von-Humboldt Foundation in 2016. As both a physicist and an entrepreneur, Jäck develops novel quantum materials for potential applications in fault-tolerant quantum computation. Jäck will join the HKUST Department of Physics as an Assistant Professor in January 2021 and focus on the research on quantum matter and microscopy in his lab at HKUST.

Prof. Adrian PO Hoi-Chun 傅凱駿

While growing up in Hong Kong, Po was a top scorer and achieved flying colors in public examinations in 2009. Although he received offers and scholarships from overseas universities, Po decided to pursue his studies in physics at the Chinese University of Hong Kong. After completing his Bachelor’s degree, Po began his doctoral studies at the University of California, Berkeley, where he worked with Prof. Ashvin VISHWANATH, a recipient of numerous prestigious awards and fellowships. In 2016, Po moved to Harvard University together with Vishwanath and completed his PhD in 2018. He is currently a Pappalardo Postdoctoral Fellow at MIT and will be an Assistant Professor of Physics at HKUST starting from March 2021.