**‘Proofing’ the future --** Eric Chitambar, assistant professor of physics at Southern Illinois University Carbondale, pauses at his office blackboard, where he is working out mathematical proofs involving quantum mechanics. The winner of a five-year, $500,000 National Science Foundation CAREER grant in 2014, Chitambar’s work is aimed at keeping information transfer safe and secure in the quantum computing environment of the future. *(Photo by* *Steve Buhman)*

June 26, 2015

**Physics research explores cyber security**

CARBONDALE, Ill. – Computers of today are governed by the laws of classical physics – the laws most people learn in high school – that describe the everyday, observable laws of nature. But the day is coming when that will no longer be true.

Even now, researchers working in the sub-atomic world of quantum mechanics, foresee a day when computers use the strange properties found there as the means to solve bigger calculations even faster than the fastest classical computer of today. Many scientists, including a physics researcher at Southern Illinois University Carbondale, believe it’s only a matter of time before this theory of quantum mechanics-based computers ‘uploads’ from the blackboard to the proverbial motherboard.

“We’re on a technological brink here,” said Eric Chitambar, assistant professor of physics, and winner of a prestigious National Science Foundation CAREER grant in 2014. “For the past 50 years we’ve been developing computers that are faster and smaller. Over time, we’re going to get down to the point that we have to deal with chips on a quantum mechanics level.

“We’re not there yet, but it’s going to happen. It’s an inevitability. So we need to understand these things,” he said.

With this massive advance, however, will undoubtedly come new threats to the way we securely transmit information every day.

Key breakthroughs in this area already have occurred, such as researcher Peter Shor’s success more than 20 years ago in creating an algorithm for quantum computers that would in theory factor numbers exponentially more quickly than any of today’s classically based computers, potentially defeating a common means of securing data today. It’s a sure bet that keeping data in all computing devices – cell phones, tablets, computers and so on – safe from hackers armed with powerful quantum mechanics-based hacking tools will be an even bigger challenge in the future.

Quantum mechanics itself, however, may offer a solution to this future problem in the form of new security paradigms that are based on both quantum and classical information principles The details of these solutions may already be residing on the blackboard in Chitambar’s office, or in one of his notebooks he uses to work out complex mathematic proofs while sitting at his dining room table. And during the next few years, he hopes to answer many such questions.

Chitambar last year received a prestigious CAREER grant from the National Science Foundation. The five-year, $500,000 grant is part of the foundation's Faculty Early Career Development Program aimed at supporting the early research and education activities of researchers who effectively integrate research and education within the context of their organization's mission.

In Chitambar’s case, the grant will support his research into information theory and finding mathematically provable ways to ensure secrecy in data transfer. His work is based on complex, even esoteric, theories that seek to meld certain aspects of classical and quantum mechanics into a unified system. Such a system might tell us more about nature, as well as provide the most important computer security upgrade of the future.

For Chitambar, it’s all about the mathematical proofs.

“Information theory is a subject that uses mathematics to describe how information is manipulated and transferred,” Chitambar said. “Within this framework, you can rigorously define the notion of secrecy and mathematically prove the security of certain tasks, such as sending an email from one computer to another.”

Classical physics, the description of nature first formulated by Newton and built on by countless other researchers during the ensuing centuries, describes the laws of nature we see in our everyday lives. But as it became possible for researchers to study nature at smaller and smaller levels, they began to see strange phenomena that did not appear to follow such laws. By the late 1920s, they begin to theorize different laws that apply at the atomic or sub-atomic level. Quantum mechanics was born.

“Quantum mechanics is a theory of nature that works very well at explaining things. It’s probably one of the best theories we have. We do many tests to verify it and it makes excellent predictions on what we actually find in the lab,” he said. “In our everyday life, classical mechanics works just fine. It does the trick. But we find that when we go down to smaller scales, that’s when things start behaving differently and that’s when we need quantum mechanics to really explain things.”

One of the laws of quantum mechanics involves the inability to measure two different properties of a quantum system at the same time. Nature somehow makes it impossible simultaneously to know both the position and momentum of such a system, for example. And that’s not just a shortcoming of research methods or technology. It’s the way nature is, Chitambar explained, and it represents a key departure from the world of classical physics.

“For example, in the classical world, if I see a car traveling by me, I can say exactly what its position is at a given time and I can measure its speed with a radar gun. It’s there and it’s going this fast,” Chitambar said. “In quantum mechanics, we have to trade off one for the other. We can either describe its position with high precision at any given time or its momentum, but not both.

“It’s very strange, and there are still many unresolved interpretations for this. What do we infer about that? On the one hand we’re dealing with things that are very small that we don’t deal with in everyday life. Then on the other hand, if we believe this is basic and fundamental, then really we are intimately connected to the quantum realm. So where does this break down? Where does this transition happen between classical and quantum world? I think these are important questions.”

Important questions, with potentially practical applications.

What intrigues Chitambar is the apparent interplay between the worlds of classical and quantum theory, as both relate to information theory. In classical information theory, “secrecy” can be characterized in terms of correlations that are shared between two parties and kept independent from any eavesdropping third party. It turns out that the mathematical theory describing these correlations looks extremely similar to the mathematical theory within quantum mechanics that describes the phenomenon of quantum entanglement.

It’s this strange coincidence that may hold the key to future computer and information security.

“My research investigates the formal connections between secrecy and quantum entanglement,” Chitambar said. “Researchers have already developed a number of analytical tools to study quantum entanglement, and I am currently discovering how these can be applied to the study of secrets and secret correlations. An underlying goal is to unify secrecy and entanglement under a single theoretical framework.”

Understood in theory by researchers starting in the mid-1990s, quantum entanglement describes two or more quantum systems in a state where it becomes impossible to treat each system independently. Subsequently, the only way to describe this new “entangled” system is as one, conjoined system.

Entanglement can provide a way of establishing security between two spatially separated parties. Entangled “packets” of polarized light known as photons, can be used to encode and carry secret messages through fiber optic networks. Once the message has been sent, the two parties must classically communicate on a secondary channel, such as common phone line or with email, to verify certain aspects of the process. This is where tools of classical information theory are needed so that the overall process can be proven as secure.

Chitambar also is working in the opposite direction, seeing if phenomena observed at the quantum level can be applied to questions at the classical level.

“We’ve developed all these analytical methods to understand entanglement, so let’s apply them to classical problems and view these in a different light,” he said. “Can we use the tools developed in quantum information to solve similar problems in classical theory of secrecy? How deep is the relationship? Is it just mathematics or is there something physically deep there?”

In some cases, he’s breaking new ground just be asking questions.

“Some of the problems I’m working on now in the classical theory haven’t even been asked before because no one really thought of them,” he said. “But the reason we’re asking now is that we found them to be very interesting in the study of quantum entanglement. We found unexpected things in the study of that phenomenon, so we’re looking at whether similar, or analogous things happen in the classical secrecy. Some cases it does, some cases we don’t know yet.”

The key to finding answers to such questions Chitambar sums up thusly: “Read a lot, talk a lot, and write a lot.” In other words, communication and networking, coupled with his own ideas on the subject, will hopefully lead him into new, productive areas of thought and theory. He will travel to conferences and seminars, as well as visiting other researchers both at SIU and abroad.

In the end, success would mean proposing new security paradigms or solving important open problems in the subject. He also hopes to discover more efficient ways of extracting information from quantum cryptography messages.

Chitambar looks at the problems as challenges he enjoys on a deep and personal level, as well as scientific.

“I like to know why things are the way they are. I want to understand what some things mean and how the universe behaves. It’s a curiosity I have,” he said. “Like a lot of theorists, I find a beauty in it and level of satisfaction when you find a solution and it’s clean and makes sense. It’s its own little rush.

“Information theory itself is extremely fascinating,” he said. “It’s a fundamental expression of the universe.”