“There are problems that are hard to solve because they have an exponential number of things to worry about,” Richerme says. “We’ve figured out a way to take a hard problem and map its behavior onto the quantum simulator, so we can do the needed calculations.”
What the simulator provides, he says, is “predictive power.” Before investing money, time, and effort into an exponentially big problem, Richerme says, “we want to know how to aim.” The simulator allows quantum scientists to test and make predictions about, for example, how difficult-to-understand molecules interact, which may be a first step in designing a new drug.
Richerme is joined in his quantum work by nearly two dozen scientists who’ve been drawn together at IU Bloomington through the campus’s Emerging Areas of Research program. In early 2018, a group of scientists led by David Baxter and Gerardo Ortiz, both professors of physics at IU Bloomington, received a $3 million award to establish a Center for Quantum Science and Engineering. The award has been a catalyst for developing a hub of quantum activity.
“The EAR award has been crucial in bringing not only physicists but computer scientists, engineers, chemists, and others to work together on new quantum problems,” Richerme says.
One of those problems is how to develop new quantum materials, materials whose quantum properties would give them special powers. Take superconductors, for instance.
Over half the energy produced in the United States is lost through heat. Think of an electronic device that gets hot while it’s charging. That doesn’t happen with superconductors, which transmit electricity without any loss to heat. But they have to be cryogenic to operate -- that is, cooled down to at least four degrees above absolute zero (-459.67 °F).
Recently, though, scientists have pushed superconducting materials to operate at much warmer temperatures, relatively speaking, which could eventually allow electricity to be transmitted over long distances without heat loss. No one is yet really clear, though, why these “high-temperature” superconductors work.
“It’s tantalizing,” Richerme says. “People were very surprised about this kind of superconductivity, and we don’t know how it works on a very microscopic scale. The reason is, to understand how it works requires keeping track of an exponentially large number of things.”
The quantum simulator, Richerme notes, can be “exceptionally good” at helping to understand and eventually design a material that superconducts at higher temperatures.
Richerme is breaking new ground in understanding the properties of potential quantum materials by figuring out how to simulate their behaviors in 2D. Most studies in Richerme’s area are done by arranging atoms, or ions, in a chain or a line, one next to the other. But when it comes to the complex world of quantum materials, Richerme says, “1D doesn’t cut it.
“It’s very hard to get a system like that to tell you anything about a true quantum material. We’ve found that all the interesting behavior happens in two-dimensional planes. So if we can understand what is happening in 2D, we’re a lot closer to figuring out what’s going on in these materials.”
Using the quantum simulator, Richerme’s lab has demonstrated, for the first time, that ions can form in a two-dimensional plane and still be quantum.
“The idea is, we can make the ions interact in the same way as a quantum material might behave and see what the effects are. Then we can apply all the things we’ve learned to do in 1D to the 2D geometry,” Richerme explains.
With a critical mass of faculty, students, and institutional support at IU, momentum is building to find “new quantum things”, Richerme says, and see what can be made of them.
“I like asking ‘why’ questions,” he says. “I think there are always a variety of explanations for any phenomenon. I don’t know what the best explanations are, but the more different ways you can understand a system, the better you can explain it to others and yourself."