Time Travel: Possible or Not?
Will it someday be possible for human beings to travel back through time? See story.
Strange Matter
After thirty years of research, internationally famous MIT theoretical physicist Eddie Farhi ’73, MS’73, still gets a charge out of solving quantum riddles.
By Tom Nugent
One summer afternoon back in 1980, two young physicists who’d been trained at Brandeis found themselves staring at a chalk-scrawled blackboard in disbelief.
Located at the world’s largest atomic-particle accelerator laboratory—the giant CERN complex near Geneva, Switzerland—the blackboard was covered with spidery equations that promised to trigger a dramatic breakthrough in modern physics.
But were those equations valid?
If they were—and this was a huge “if”—the implications for the arcane science of particle physics were staggering.
One of the two physicists who stood gaping at the CERN blackboard on that afternoon twenty-seven years ago was Edward Farhi, and he was doing his best to remain calm.
Farhi had grown up in a working-class family in the heart of one of New York City’s toughest neighborhoods—the rough-and-tumble South Bronx—before landing a coveted slot at the famous Bronx High School of Science. It was at Brandeis, though, under the tutelage of idealistic professors and mentors like the late Stephan Berko, Allen Mills, and Rick Heller, as well as Hugh Pendleton III and Sam Schweber [now professor emeritus of physics], that he became inspired.
Indeed, as director of the prestigious Center for Theoretical Physics at the Massachusetts Institute of Technology (MIT), Farhi is today a renowned scientist who is helping to pioneer the development of quantum computers—an entirely new kind of computing machines that promise to be immensely faster and more efficient that today’s desktop PCs.
Back in 1980, however, the young Farhi—who’d received a physics PhD from Harvard just two years earlier—took a long, hard look at his equations. And although the mathematical operations that he and his colleague, physicist Laurence Abbott, PhD’77, had employed were mind-bendingly complex, the bottom-line result seemed strikingly clear.
According to the calculations on the board, the mysterious and infinitesimally tiny atomic entities known as “quarks” were composed of even smaller fragments of matter—a finding that would challenge the basic Standard Model of contemporary particle physics itself.
Formulated during the 1970s, the Standard Model is regarded as the cornerstone of modern particle physics. According to the model, matter consists of twenty-five fundamental particles, including electrons, photons, gluons, and neutrinos. In this group also are the tiny quarks, considered to be autonomous and indivisible.
The Standard Model has ruled particle physics for nearly forty years, but at CERN in 1980, Farhi and Abbott believed they were on the edge of a paradigm shift—a breakthrough that would require revising some of science’s basic understanding of material reality at the atomic level.
Although their new theory made predictions that were ultimately not borne out by experiment—leaving the Standard Model firmly in place—the two investigators experienced what they still describe as “the thrill of a lifetime” during their time together at CERN. In fact, Farhi and Abbott remain close friends.
“That was an exciting time for us,” says Farhi, leading a tour of the MIT center where he and thirteen other professors work daily at the cutting edge of quantum physics along with a large group of postdocs and graduate students. “Larry and I were still in our late twenties back then, and it seemed we were coming up with new ideas almost every day.”
“The more we looked at the data and studied our equations, the more it seemed to us that quarks—which were supposed to be elementary, indivisible particles—could themselves be made of other things. And because we were so young, we were arrogant enough to believe we were onto something huge. It was a wild idea, and we had a lot of fun. For a while there, we were thinking we might actually be able to explain something in particle physics.”
For his part, former Brandeis physics professor Larry Abbott, now a professor of biophysics at Columbia University, remembers their struggle to upend the Standard Model as “a very unorthodox attempt to stand the accepted theory about quarks on its head.”
Having your theory shot down, Farhi points out, isn’t necessarily a bad outcome for a particle physicist who’s interested in exploring new ideas.
“In this kind of research,” he explains, “you just try to get a good swing at the plate—and you don’t worry too much if the ball gets caught in the outfield. We took a great swing with our theory, and that was the important thing.”
Still Swinging
Although Farhi hasn’t managed to overturn the Standard Model yet, he has continued to take great swings, keeping up a steady stream of cutting-edge research while teaching such esoteric subjects as quantum mechanics, quantum field theory, and general relativity at MIT since 1982.
As an investigator, Farhi has analyzed phenomena related to astrophysics (he and collaborators proposed a new type of massive object called a “Strange Star”) to cosmology (asking, along with MIT’s famed Alan Guth, whether a new universe could be made in a laboratory) and to Einstein’s theory of general relativity (is a time machine really possible, or do the laws of physics prohibit it?).
And while managing to capture three different teaching awards at MIT he’s also found time to publish dozens of articles in the world’s leading scientific journals.
Farhi has worked on a series of grand unified theories that attempt to put all the forces of nature into one set of equations. He has also studied the properties of a super-dense form of elementary particles known as “Strange Matter.” While working on his PhD thesis, he invented a way of measuring the closeness of particles coming out of high-energy accelerator collisions by calculating a new variable he called thrust. His method of measuring thrust, which can be computed using the Standard Model, will be put to work by experimentalists at the giant new Large Hadron Collidor at CERN.
Celebrated as one of the world’s most creative and influential particle physicists, Farhi also works in the field of quantum computing, where he’s widely regarded as a major pioneer.
Two years ago he was selected by MIT to direct the Center for Theoretical Physics, which sponsors some of the planet’s most advanced research on particle physics and quantum mechanics.
Quantum Computers: The Next Big Thing?
Farhi lives in a world of scribbled algorithms and wall-to-wall physics equations. Drop by his office on the campus of MIT during a typical weekday morning, and the odds are high that you’ll find him standing in front of a blackboard struggling to produce math equations related to the potential use of quantum computers.
“Lately, I’ve been developing new algorithms for quantum computers. This is some of the most exciting new computer-research being done in the world today and I think we [at MIT] have had a pretty big influence on the development of quantum computers. I feel very proud of our work in this area,” he says.
As Farhi describes them, quantum computers promise to revolutionize computation in the next few decades not because these new machines will do the same things as the lumbering data processors of today while operating millions of times faster, but because they will accelerate the process multifold by taking a more efficient and intelligent route to the solution of a problem.
According to Farhi, quantum computers will operate on an entirely different principle from today’s processors, which rely on manipulating tiny electrical charges that represent strings of ones and zeroes as basic units of information. Quantum computers, on the other hand, will take full advantage of the quantum nature of matter at the automic level.
It has already been shown that, if a quantum computer could be built, it would be able to break all existing codes used by banks and the military. For that reason, the U.S. government is joining the race to build quantum computers by funding scientists like Farhi.
An exciting prospect? You bet. But Farhi is quick to point out that these super-machines are still on the scientific drawing board.
“It’s important to remember that no one has actually built a quantum computer yet,” he says with a wry chuckle, “so we’re talking about programming a machine that doesn’t exist.
“Still, there’s no doubt that quantum computing is going to happen, even if it’s a few years off, and when it does, the power of these machines will be immense, so they’ll be able to perform computing tasks no one has ever thought possible.”
Ask Farhi to explain the workings of a quantum computer, and the physics guru lights up like Boston’s Fenway Park during a night game.
“A quantum computer wouldn’t use strings of bits, like today’s computers,” says the excited physicist at one point. “Instead, it would rely on ‘qubits’—quantum bits—built from what we call ‘spin-one-half’ particles.
“You can think of ‘spin up’ as being a zero, and you can think of ‘spin down’ as being a one. But the quantum particle can exist in a state that’s neither spin up or spin down, but rather in a state of ‘superposition.’
“We can also make superpositions of ensembles of qubits and, by taking advantage of subtle quantum effects, turn this to our computational advantage. In fact, my group at MIT has just shown that the problem of determining who will win a game like chess can be sped up by quantum computing.”
If this seems just a bit complicated, things get even stranger when Farhi is asked whether the fact that qubits can apparently be in two states at once implies that we’re living among a series of “parallel universes.” Are we actually surrounded by adjoining universes in which near-duplicates of ourselves are struggling to understand the quantum physics of their worlds?
Farhi doesn’t miss a beat as he responds, “Let’s just say that I believe in the existence of the parallel universes formally, okay? In other words, I believe it mathematically —but I don’t really think it has much bearing on the science we do. I find it mind-bending, as a concept, but I don’t think it will help me work out my equations.”
“Eddie won’t tell you this, because he’s too modest,” says Larry Abbott, “but he’s actually way out in front of everybody else in the area of quantum computers. If anybody can make it happen, I’m betting that it will be Eddie.
Tom Nugent is a free-lance writer based in Michigan. His work has appeared in the New York Times, People, and the Detroit Free Press.