$7.5M DOD MURI award to explore creation of qubits based on Majorana zero modes

4/15/2022 6:30:44 PM

Jenny Applequist for the Coordinated Science Lab

IQUIST’s Angela Kou will analyze proposed materials and investigate qubits’ limitations

Illinois Physics and IQUIST Professor Angela Kou
Illinois Physics and IQUIST Professor Angela Kou

Qubits lie at the heart of quantum computing—and they aren’t all the same. The quantum successor to classical computing’s bits, they can be created in a variety of ways that have yet to be fully explored. The chosen approach matters, because it has implications for how robust the resulting qubit will be and how well it will perform.

The Department of Defense’s Multidisciplinary University Research Initiative (MURI) has just announced a $7.5 million project that will explore one intriguing option: qubits based on Majorana zero modes (MZMs). MZMs are zero-energy quasiparticles with special properties that suggest they could be used as the basis for very good qubits. For example, MZMs "remember" their movement history, which makes them robust to local noise and errors and potentially good for long-term storage of quantum information and more accurate quantum processing.

New York University’s Javad Shabani will be the principal investigator of the six-university project, and a key piece of the work will be led by UIUC’s Angela Kou, who is an assistant professor of physics and a member of the Illinois Quantum Information Science and Technology Center (IQUIST).

What kind of platform provides the best way to realize MZMs? It remains an open question. Kou explains, “For our project, the goal is to look at a particular type of materials system and try to refine it, then to find better ways of detecting these Majorana zero modes to make sure we have lots of evidence to support that the Majorana zero modes [do] exist in these types of materials. And then, once we are reasonably certain that they exist in these materials systems, [we will] try to build a qubit out of it and do some manipulations on the qubits that are formed from these particles.”

More specifically, the team will create a hybrid system in which a superconductor is layered on top of a semiconducting material—and it won’t be an easy task. “To make these particles arise, you have to understand the semiconducting system really well, the superconducting system really well, and also the hybrid system really well,” says Kou. Thus, the project will require the researchers to develop a better understanding of the different materials used, and what happens when they’re coupled together.

Superconducting circuits are a major focus of Kou’s research group at UIUC. She and her students make circuit elements, such as inductors and capacitors, out of superconductors, which have extremely low loss; that makes it possible to probe different kinds of materials very precisely. In that context, for the MZM project, Kou will study materials that are composites of semiconductors and superconductors, trying to figure out how they behave and what can be done to make them better.

In a second part of the project, she will work to understand what limiting factors would affect a qubit built from MZMs. In particular, she’ll try to measure the time scales over which it will be possible to use MZM qubits in a noisy environment before the environmental noise impacts their performance.

Out of approximately 340 proposals received for the fiscal year 2022 MURI competition, this project is one of just 28 that were selected for funding. The winning teams represent 63 U.S. academic institutions and together will receive $195 million. As per MURI’s mission, all of the projects will pursue basic research that spans multiple scientific disciplines.