# The Next Space Race

Quantum information science has been called the next technological “space race.” And the University of Illinois has positioned itself to be at the forefront of that race.

November of 2018, the U of I pledged $22 million for the formation of the Illinois Quantum Information Science and Technology Center (IQUIST). Two of the leading experts in the field, Illinois physics professors Brian DeMarco and Paul Kwiat talked to us about its vast future applications. Both professors represented the University of Illinois at the first ever Chicago Quantum Summit. DeMarco was invited to the Advancing American Leadership in Quantum Information Science Summit at the White House, Kwiat leads the Science Definition Team for NASA’s Deep Space Quantum Link study, and together they participated in all three recent NSF Quantum Accelerator Scoping Workshops.

### Tell us a little bit about your background.

**BRIAN** - I grew up in upstate New York, got into physics at a young age, and fell in love with quantum science as a college student. I became permanently hooked on quantum physics while completing my PhD. After my PhD work, I was a postdoc with (2012 Nobel Prize in Physics winner) David Wineland at the National Institute of Standards and Technology in Boulder, where I worked on building some of the first rudimentary quantum computers. I came to the University of Illinois in 2003 and have been here ever since!

**PAUL** - I grew up in the Midwest and after leaving Ohio, swore I would never come back to the Midwest, but here I am since 2001. I was studying some basic fundamental physics things as a graduate student about how to make entangled states. People began to realize that you could use those entangled states, for example, for doing secure communication (quantum cryptography). Then I did a two-year postdoc position in Austria and afterwards went to Los Alamos National Laboratory for six years, where I worked with groups doing both quantum computing and also quantum encryption.

### Give us the skinny on quantum mechanics.

**PAUL** - Quantum mechanics really started at the beginning of the last century, when people realized that small particles like electrons and single particles of light—photons—can behave very different than other objects. Because they act like waves, they can in some sense be in multiple places at once, and that fact allowed us to understand why there are atoms and how they interact. That knowledge played a huge role in technology, allowing things like microelectronics and transistors, lasers, and MRIs. Those are all quantum mechanics-based technologies that had tremendous technological importance for people’s lives. People typically call this the first quantum revolution, when people were first discovering quantum mechanics.

However, there were other key aspects of quantum mechanics that actually weren’t a part of the technology that we use—entanglement is probably the best example. Particles can be entangled quantum mechanically and that allows them to have amazing correlations no matter how far apart they are. Maybe the simplest example is if you and I each have a six-sided die, and in our separate rooms we’re each going to roll our die, and then compare the results afterward. Astoundingly, we find out that although we’re each equally likely to get 1-6, we always get the same number, which should only happen 1/6th of the time. The correlations enabled by entanglement are simply completely impossible from usual ‘classical’ physics. And it turns out you can use that for things in information processing; that sort of realization is what led to the second quantum revolution.

**BRIAN** - Starting in the 1980s, people began to suspect that you could use quantum mechanics and quantum entanglement to enhance the power of computers, and physicists subsequently developed the idea of a quantum computer.

This concept originated during a talk in 1981 by Nobel laureate Richard Feynman at Caltech University, where he proposed that you might need a quantum computer to solve some of the stickiest and hardest problems in quantum mechanics. And those problems are directly relevant to many practical applications.

Before we discuss what a quantum computer is or what it could be, it is useful to describe a conventional computer. Inside a computer, there is memory. That memory is made up of bits, and those bits can store two values: 0 or 1. Bits can be grouped together to make numbers, like integers, or even decimal numbers. The bits can also be organized into instructions for what is called the central processing unit (CPU). When you work with a computer, you provide input (using, for instance, your keyboard). That input tells the CPU to read the bits in the memory, follow the instructions, do a calculation using the numbers stored in the memory, and then return an output.

There are some important problems that are too hard for even our largest supercomputers to solve. Examples of hard scientific problems include simulating exotic materials like superconductors and determining the properties of photosynthetic molecular complexes. A more familiar challenge is the “nurse scheduling” problem. Let’s say that you run a hospital staffed by 1,000 nurses. Part of your job is to create a schedule that covers all the shifts while meeting constraints such as vacation and sick leave. Completing that task in an optimal way is especially challenging to solve using conventional computers.

A quantum computer can solve these types of problems at scales inaccessible even to conventional supercomputers. At a high level, a quantum computer shares many features with a conventional computer, such as a processing unit, memory, inputs, and outputs. But, instead of using bits, a quantum computer has quantum bits, or “qubits,” that can be simultaneously store 0 *and *1, and all kinds of different combinations. And qubits can be quantum entangled with one another.

### Why can quantum computers solve these problems that even supercomputers can’t?

**PAUL** - We don’t have all the answers to that question, but there are some things that we know they can do faster. Let’s just say we want to keep track of a typical kind of qubit, the “spin” of an electron. Every electron looks like a magnet and just for the sake of the argument, let’s say you have a chain of these electron spins and all you want to do is keep track of 300 of them being up or down. It turns out that would take 2300 (the same as 1090 ) numbers just to represent all the possible configurations of those quantum spins—that is more numbers than there are particles in the universe. So just representing that number of what those quantum spins are doing would be impossible with any conceivable supercomputer. That is just one example of why quantum computers are more powerful—they can run algorithms on an extremely large number of numbers simultaneously.

### Why is the field of quantum computing growing so rapidly?

**PAUL** - Historically, the breakthrough moment came with Peter Shor’s factoring algorithm, which showed you could factor large numbers quickly on a quantum computer; the reason you should care is that the supposed difficulty in factoring large numbers basically underlies the encryption used to secure every email you send, or any online credit card transaction you make—these assume that factoring is a hard mathematical problem. If I give you a 100-digit number and ask you to factor it, you can’t do it quickly with any computer we currently have. But Shor’s quantum factoring algorithm could. And right around the same time he proposed it, other people realized one could use ions (atoms with an extra electron or proton) in a trap as quantum bits.

In fact, trapped ions are certainly one of the most viable quantum processor candidates now, in terms of the number of qubits they’ve been able to entangle—they can connect 40 or 50 of these quantum bits together.

**BRIAN** - A different technology has reached a similar level—superconducting transmon qubits. Several companies, including IBM and Google, are now building systems based on that platform. Google recently succeeded in creating at 53-qubit device that cannot be simulated efficiently using a classical supercomputer, a milestone called quantum supremacy. We are still far from a device that is useful for practical applications, however.

These recent advancements have caught the attention of Fortune 500 companies and scores of small startups who all hope to develop quantum technologies that drive the economy over the coming decades.

### What were the takeaways from the White House Summit?

**BRIAN** - That was an exciting event and was aimed to highlight this emerging research area and to provide Congress the boost it needed to pass the National Quantum Initiative, which was signed into law by President Trump on December 26, 2018. At the White House Summit, there were leaders from industry, including IBM, Google, and Microsoft. There were also professors like me, who work in this research area. And, stakeholders from the Department of Defense, where many of the applications from quantum technologies have high impact.

At the event, we participated in breakout sessions and panel discussions. A highlight for me was a session on preparing the future quantum workforce. We need to have a quantum-smart workforce ready for quantum technologies to contribute to the economy 10 or 20 years down the road. One of the reasons Ed Seidel [Vice President for Economic Development and Innovation for the University of Illinois System] and I were invited to the Summit is because of our fantastic Grainger College of Engineering, with its highly ranked and large electrical and computer engineering, physics, and computer science departments. It’s the convergence of these areas that is needed to drive quantum computing and technology to the next level.

### Can you talk about IQUIST (Illinois Quantum Information Science and Technology Center), and the importance of the timing of its formation?

**PAUL** - We were very grateful that the university made this investment—it certainly could not have come at a better time. If it had come a couple of years later, it would have been too late, considering the tsunami of interest in this area. Quantum information research in space is a clear example. A few years ago one of my colleagues in China launched a satellite that demonstrated quantum communication from space to the ground for the first time. The things that they did may not have been practically useful yet, but they were done to demonstrate a proof of principle, and certainly attracted a lot of attention. There is a now a huge effort in quantum communication going on in China, Japan, and all of Europe. The U.S. has been a little more conservative up to this point, but I believe now that the anchors have been lifted, the U.S. is going to take off at high speed. It could have been the case that the rest of the world was taking off while we at Illinois were still putting on our running shoes; in that case, we basically wouldn’t have been able to participate, but as it is, we’re right at the starting block with the other key runners.

In some sense we have an advantage due to the research we already had here. At our first all-hands IQUIST retreat we had roughly 30 people on campus, many of whom aren’t in physics but contribute to quantum information science in some way. In order to grow that effort, IQUIST is making many new hires, across multiple departments.

For example, in the past year and a half we’ve hired 4 new faculty, in physics and electrical engineering. And we’re now looking to expand even further, with ongoing searches in computer science and math, in addition to electrical engineering and physics. Overall, we’re looking to add 10-ish faculty across multiple departments, and that is critical because the time is over for quantum information research done only in the physics laboratory. Of course, we still need to do that fundamental research, but now we also need to start doing engineering in the quantum space —for computing, but also for communication and sensing. Some of these may have more impact on people than even quantum computing—I don’t see a time when everyone is going to have their own quantum computer, but I could easily imagine a scenario where everyone has a small quantum sensor, and maybe they have some way of quantum linking them via the quantum cloud, and being able to run their programs on a quantum computer that’s located somewhere else. To do all that, you really need a quantum network.

### Outside of computer science, electrical and computer engineering, and physics, what areas do you see being touched by IQUIST?

**BRIAN** - We are collaborating with researchers in math to understand how much information can be packed into a quantum system, which is a question with broad ranging implications. There are also ties to chemistry, since one of the applications for a quantum computer could be determining better than any supercomputer the properties of molecular compounds. Quantum computers could also help solve certain problems in aerospace engineering, such as turbulent air flow. Similar application spaces yet to be discovered could provide a for IQUIST to connect across the university.

### What is going on right now in your lab and what way are those discoveries going to impact the growing quantum revolution?

**PAUL** - My research has quite a range, from very fundamental things—like how to understand this phenomenon of entanglement when you have ever-larger systems, how to best characterize it, and what it might be good for—to more immediate practical applications. For example, we have some money from the U.S. Navy to develop drone-based quantum cryptography and communication. That could make a much more flexible system and be a stepping stone for developing quantum networks.

### Beyond Illinois, the Midwest seems to be a hotbed of activity in the quantum space, i.e. the Chicago Quantum Exchange.

**BRIAN** - I think that is exactly right. In fact, I joined a group from Illinois institutions (Argonne, FermiLab, University of Chicago, Northwestern

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