Try to simulate interactions among more than a few of the atoms and other tiny particles that make up matter and the universe down on the quantum level, and you've quickly outrun the capabilities of even the most powerful supercomputer.
There's just too much stuff interacting in too many ways, some of them bizarre from our perspective, for a conventional computer to process these "many-bodied problems" in the lifetime of not just one researcher, but a whole lot of them.
Quantum particles can be in more than one state at once, among other things, and linked together in their orientation over vast distances, properties called superposition and entanglement respectively.
In 1982, the famed physicist Richard Feynman proposed a solution to the problem of simulating the quantum world – use quantum particles themselves to do the computing.
For example, in classic computing, computers work by combining zeros and ones into code that tells the machine what to do. But those "bits" can symbolize only a single thing at a time, a zero or a one, true or false, yes or no.
In theory, superposition could allow every combination to be processed simultaneously, because quantum bits are in all states at once, making everything work exponentially faster.
Anything like a viable, general-purpose quantum computer is probably a long way off.
But University of Illinois Professor Brian DeMarco thinks he's on a course to having something like a special-purpose quantum computer, designed to simulate many-bodied problems, in the next decade.
Those problems have importance not only because they plague physicists, said DeMarco, a UI physics professor. They're at the root of questions about how superconductors function, for instance, and also are integral to materials research.
"They're important to our understanding of nature as well as for practical reasons," DeMarco said.
Consciousness itself may be a many-bodied problem, in the view of some researchers, although DeMarco is skeptical about that notion.
DeMarco's work got some notable attention this month. He was selected the winner in his category in the Young Scholars Competition at an international symposium called Amazing Light: Visions for Discovery.
The gala event at the University of California, Berkeley, honored the 90th birthday of Charles Townes, the Nobel Prize-winning inventor of the laser.
Another UI physicist, Paul Kwiat, placed third in his category. The UI was the only school nationwide with two winners among the 18 finalists in three categories.
It was the first time anyone had handed DeMarco, 31, a check for $20,000 made out in his name. But he may have been just as excited to be around the worldwide collection of leaders in a variety of scientific fields who assembled for the symposium.
"It was very stimulating," he said.
Lasers come into play in DeMarco's research, which involves working with gases such as rubidium, a naturally occurring metallic element akin to sodium that can be a component in salt in its solid state.
DeMarco and colleagues cool those gases to almost "absolute zero," or about minus 460 degrees, at which point they begin to behave quantum mechanically. Little wonder a sign on his lab door jokes that it's, "The coldest place in Champaign-Urbana." Even in January or February.
They then trap the super-cooled gases in a magnetic field and shine a laser on them. The atoms that make up the gas scatter the light, in essence give off shadows, which the UI researchers capture with a specialized camera.
"We get all our data from the photographs," DeMarco said.
The technique gives the researchers a window on the quantum world. Eventually, they want to use the trapped atoms as models to simulate quantum properties of other materials, albeit by analogy rather than using the particles as bits to compute a simulation mathematically as digital computers do.