Nineteen-hundred-and-five is remembered as Albert Einstein's magical year - the one in which he single-handedly changed our understanding of the universe with revolutionary papers on light quanta, Brownian motion and special relativity. Only 25 when the first of the three papers was published, Einstein tackled the biggest problems in physics at an age when most young scientists are working as research assistants.
As he nears the end of his celebrated career in academia, Karl Hess is poring over copies of Einstein's hand-written notes in German from that era as he searches for revelations from one of the great debates in physics. Einstein and fellow physics icon Niels Bohr had a running disagreement over several years regarding hidden variables, a concept Einstein argued was necessary in order to fully complete quantum mechanical theory.
The debate and its subsequent permutations over the decades continue to generate considerable discussion in physics; it caught Hess' attention during his early years as a student and teacher in his native Austria. But, like most scientists, Hess devoted the formative years of his academic and research careers to problems less esoteric than hidden variables, or what Einstein called "spooky action at a distance." Hess focused primarily on transport of electrons, and became a leading theoretician in the realm of semiconductor transistors just as ever-shrinking transistors were fueling computers with ever-greater processing power in the latter part of the 20th Century.
It wasn't a coincidence that the theoretical mind behind the invention of the transistor, John Bardeen, was largely responsible for Hess' presence at the University of Illinois at Urbana-Champaign. With the help of Bardeen, already a two-time Nobel Prize winner at that point, Hess left a teaching position in Vienna to work first as a postdoctoral researcher at the U of I and, later, as an associate professor of electrical engineering.
Today, Hess is regarded as one of the world's foremost experts in the area of electron transport and owns the rare distinction of being chosen as a Fellow at both the National Academy of Sciences and National Academy of Engineering. He played a key role in the creation of an interdisciplinary research center at the University of Illinois, and when that center became the Beckman Institute for Advanced Science and Technology, served as Associate Director and then as Co-chair of the Molecular and Electronic Nanostructures research initiative from its inception.
In May, Hess will end almost 30 years as a professor and researcher at Illinois with his retirement from the University. A two-day Karl Hess Symposium and celebration at the Beckman Institute will spotlight his contributions to the disciplines of physics and engineering, and to the fields of computer simulation, optoelectronics, and quantum computing, among others.
The symposium may serve as a punctuation point to his career at Illinois but retirement for Hess involves only his teaching and administrative duties. His research will continue, but perhaps with a little different focus. Gone will be the need for writing grant proposals, or worrying about more mundane research questions. Retirement in Hess' case means tackling a big question in physics, the same one that Einstein, Bohr and countless other scientists discussed over the years, and one that consumed him for the last few years of his academic career.
"The question is this influence at a distance that, according to Einstein, is a trademark of quantum mechanics," Hess said.
Quantum mechanical theory was incomplete, Einstein argued, unless you account for hidden variables that make it possible to rule out "spooky action at a distance" as part of the theory's explanation of how the world of atomic and sub-atomic particle physics works. Einstein and his followers maintained that a hidden variable theory without influences at a distance was possible. A suite of later theories, based on Bell's Theorem, argued that a "Local Realistic" interpretation of quantum mechanics like Einstein's was impossible.
It was during his role as chair of a committee formed to foster ideas for interdisciplinary collaborations for the soon-to-be Beckman Institute that Hess first became interested in Bell's Theorem. Future Nobel Prize winner Tony Leggett of the University of Illinois gave a presentation on the subject in the mid 1980's and showed Hess that Bell's Theorem was an interdisciplinary topic encompassing mathematical, physical and statistical elements.
"That presentation by Leggett totally took me by surprise and captured my interest," Hess said. "Since that presentation I have not let go thinking of it."
But Hess didn't seriously begin tackling the subject until about seven years ago, and since then has thought of little else. "I had five years of almost unremitting thought of it," he said. "Now I feel that Walter Philipp and I have solved the problem pretty much, at least one aspect."
Hess has worked with Philipp, a Beckman colleague and mathematician, on a solution he describes this way: "What we did is we found a way to explain the Bell Theorem without action at a distance. We don't say that it's wrong but we have an explanation for it and a mathematical way of showing it without any influences at a distance."
Hess started off by asking the question of what is quantum computing, and the answers he and Philipp are seeking could provide insights into the future of computing at the quantum level.
"In this asking process I saw that everything leads to one question and that question is either decided or not decided by the theorem of Bell," he said. "Our work at least points a way that one can explain quantum information in ordinary terms. People say quantum information is something entirely new; it's different from digital or analog information.
"We think we've found a way to link it to digital and analog information. In our opinion - and we think we're right but nobody really knows and lots of people disagree - but in our opinion it can be expressed in terms of digital and analog information. In that respect the quantum computer would be just a different computer but not something entirely new."
Hess said his theory includes time dependencies, which Bell's Theorem did not. The latest paper by Hess and Philipp on the subject is titled "The Bell Theorem as a Special Case of a Theorem of Bass." His current research focus is controversial but Hess emphasized that in spite of that - or maybe because of it - the topic is still the one that interested him most in his career.
"I have to tell you Tony Leggett doesn't like what I am doing. He started me off but he doesn't agree with it," Hess said.
At this stage, Hess isn't bothered by criticism. His list of accomplishments is towering in the fields he has entered. Hess came along after the inventions of the transistor and the integrated circuit, but his theories helped to explain how they worked at the most basic level and how they could be improved. He developed a full-band Monte Carlo method for simulating designs of new generations of transistors on chips, an important tool for lowering cost and adding computing power. His work on real space transfer was crucial in understanding layered semiconductor technology. Hess brought computer-aided design and computer simulations to optoelectronics such as CD players, another cost reduction factor among other benefits, to that field.
Even though he is a theorist, Hess has always been mindful of the need to consider potential applications when doing research. That perspective was born in his youth, not long after he read a book on inventions as a 7-year-old in Vienna.
"From my earliest youth, I always wanted to do something that was useful for people," Hess said. "I always had some purely mathematical interests in my student years but I figured that is not where I want to spend the bulk of my life. I wanted to do something that is useful, at least see some immediate application of it, some technological basis."
That desire to find an application started early. After reading a chapter on electricity from that 1901 book on inventions, Hess built a microphone. Many years before Arnold Beckman had a similar experience, doing chemistry experiments at a young age after reading a textbook on that subject at age nine.
"I think these are very important experiences," Hess said. "If I had not found that book I probably would not have gotten interested in electricity."
That interest continued in school. In high school, Hess heard lectures by Erwin Schrödinger, Nobel Prize winner for Schrödinger's Equation, and one of the fathers of quantum mechanical theory. In college Hess earned a doctorate in physics and mathematics from the University of Vienna.
Hess met Bardeen when the U of I professor was traveling in Europe and fresh off the 1972 Nobel Prize in Physics for his work on superconductivity. Hess did some translation work for Bardeen, who in turn helped to obtain a Fulbright Scholarship for him and a postdoctoral position at Illinois in electrical engineering.
"He was very helpful from the beginning, although it was clear after a few weeks that I would not work in what he was interested in," Hess said. "By that time he was not interested in semiconductors anymore."
Hess returned to Austria but always hoped to come back to America. In 1977, he got a faculty position at Illinois as a visiting associate professor. The "visiting" turned into permanent status in 1980 after Hess had started a very successful collaboration with Ben Streetman that led to the work on real space transfer.
Hess said Streetman was a big influence, teaching him the ways universities work in the United States, and was probably the person most responsible for him becoming a full professor.
Hess also kept in close contact with Bardeen, who was one of the best-known scientists in America at that time. Hess was a little bit in awe of him and the fact that Bardeen, who avoided small talk, was uncomfortable in many social situations didn't help their early relationship.
Hess eventually learned to avoid the small talk and concentrate on science with Bardeen, and a friendship developed. On the research side, most of Hess' early work at the U of I was with C.T. Sah, the co-inventor of complementary metal oxide semiconductor (CMOS) theory, which is the basis for most current chip technology. Together they solved the Boltzmann transport equation for transistors, something Hess cites as one accomplishment he is very proud of.
"We basically developed together the first electronic transport theory, which included both quantum effects and the Boltzmann transfer equation, which is not an easy combination," Hess said. "So it was the first bigger model on MOSFETs on the basis of the transport equation."
Over the next few years, Hess became involved in numerous projects, including the work on real space transfer, the full-band Monte Carlo method, laser simulation, and optoelectronics. Hess said that graduate students played a key role on all of those projects. "I had very talented graduate students in all the areas I worked in. I owe them big-time," he said. "The hallmark of the U of I is we have great graduate students and 80 percent of the work could not have been done without them."
Those who have worked with Hess feel they owe him just as much. Slava Rotkin, a professor of physics at Lehigh, was a Beckman Fellow and researcher at the Institute who collaborated with Hess on nanotube device physics and nanoscale transistors, among other topics. Citing the ties to Schrödinger, Bardeen, and others, Rotkin said Hess is a "direct descendant of the giants of semiconductor device physics."
"For me it was indispensable experience to work with Karl. The years at Beckman laid out a foundation for my research for the next few years. And if I succeed in my research work, I am sure a great part of this success would be thanks to Karl."
Rotkin said Hess is more than a great scientist. "He is one of the most pleasant people I have ever met. We had chances to communicate in both a scholarly atmosphere and outside the office. He is a very intelligent person, knowledgeable in many things beyond physics. He has a great sense of humor and a great passion for his family."
After arriving at Illinois, Hess' reputation grew quickly, enough so that when discussion of a new interdisciplinary research center began on campus in the early 1980s Hess was chosen to head one of two committees formed to write proposals for such a facility. Current Biological Intelligence Co-chair William Greenough headed the other committee.
"He was seen as competition," Hess said of Greenough's committee. "We thought if we just work on our proposal hard enough they won't take the other proposal and Bill thought the same way. I know that because we are good friends."
The two proposals were eventually combined, but Hess said some of the original ideas for the center were a bit too grandiose. At an early meeting on the topic, many in the room thought research could be pre-ordained in a certain direction. Bardeen gave Hess some useful advice in that regard.
"When we walked out of the meeting Bardeen took me aside and said 'If you start research like that it will fail miserably,'" Hess said. "I said 'why John?' And he said 'because intelligence is such a complicated thing you cannot say I will go and do this (certain) research on intelligence. You have to start from the bottom up.' I listened to him and we scaled down our expectations quite a bit."
Even so, when the Beckman Institute opened in 1989, it was a unique center for research, combining the physical and life sciences in ways that had never been done before. Ted Brown, who was then Vice-Chancellor for Research and later became Beckman's first director, said Hess has been an integral part of Beckman ever since it opened, both in terms of research and in his leadership role at the Institute.
"Karl has meant so many things to the Beckman Institute," Brown said. "Karl provided the strong intellectual leadership required to synthesize the views of many diverse faculty and administrators into a single coherent image. When the Institute was up and running (Karl and Bill) served for several years as Associate Directors, and helped immensely in shaping the nature of the Beckman Institute in its formative years."
Beckman Institute Director Pierre Wiltzius said Hess cast a giant shadow.
"Karl is an irreplaceable asset who helped shape the Beckman Institute as much as anyone in its history," Wiltzius said. "He has that rare combination of being a great man of science and a visionary. I greatly valued his insights and advice. He also is one of the finest people you will ever meet and he will be greatly missed at Beckman."
Hess feels lucky to have been a part of a place like the Beckman Institute.
"That was one of the greatest experiences of my life, there is no doubt about it," Hess said of his time at Beckman. "I felt that the United States is where the action was and the people were, and it was already a big fulfillment of a wish when I got the position here at a great university. Then to be in a project of that university of such a magnitude, that was a fulfillment of my wildest dreams. I was enthusiastic from the very beginning. Most of my colleagues, strangely enough, didn't share my enthusiasm."
Hess said his colleagues thought he was wasting his time working to bring an interdisciplinary center to Illinois. "But it was just the opposite. I can say it was the most exciting time of my life."
Retirement doesn't look to be any less exciting for Hess. He enjoys listening to Mozart and playing chess on the computer. But a thick stack of papers inside a manila folder on his desk at Beckman is calling. In it are references to Bell's Theorem and hidden variables and other ideas that fuel Hess' imagination just as much as the concept of electricity did for him as a 7-year-old. There may be other projects and roles to play in the future, but discovering how the world works will always define Karl Hess.
"That folder has all the projects I plan to do for retirement. I am not going to be bored. I will have enough to do, I think," he said with a laugh.