New tool creates and characterizes quantum materials and devices

To fully unlock some of the most exciting quantum technologies like superconducting qubits and next-generation quantum sensors, researchers are on the hunt for new, uniquely suited quantum materials.

But much still needs to be learned about these materials and how they can be best used to create quantum devices.

Shuolong Yang
Asst. Prof. Shuolong Yang

Researchers at the Pritzker School of Molecular Engineering (PME) at the University of Chicago have developed a tool that can both create and characterize quantum materials, then use them to 3D-print quantum devices.

The system, called multi-resolution photoemission spectroscopy (MRPES), probes quantum materials in energy, momentum, space, and time using three light sources in one setup. It can capture electron dynamics at a speed of 35 femtoseconds — perhaps the fastest such system in the world — and researchers plan to use it to create quantum devices such as superconducting qubits.

“This is truly a multi-modal quantum device characterization instrument,” said Asst. Prof. Shuolong Yang, who led the research.It gives us a new level of adaptability and control that will allow us to unlock new quantum technologies.”

The research was published in the journal Review of Scientific Instruments.

Using light to understand quantum materials

Quantum materials — a broad class of materials in which quantum mechanics plays a role in their properties and behavior — are incredibly fragile and must be created in a vacuum. But to test and characterize these materials, scientists often must move the materials from where they were developed to a separate testbed.

Yang’s instrument combines both materials creation and characterization into one tool, essentially creating a production line of quantum materials.

“We can move them back and forth between chambers in the system without compromising their properties,” he said. “It becomes very efficient.”

To characterize the materials, the MRPES system uses lasers to shine photons onto quantum materials, which allows researchers to analyze the behavior of the electrons within the material. The spectroscopy tool records information from these materials in both time and space by using femtosecond light pulses. (A femtosecond is one millionth of one billionth of a second.) This is the timescale within which electrons move: the time it takes for an electron to scatter off an impurity within a material is, on average, 50 femtoseconds.

MRPES is essentially a superfast camera that can capture an electron event that happens in 35 femtoseconds — the fastest time recorded with such a tool using nonlinear optical crystals.

“It’s like having a fast enough frame rate to capture the wing movements of a hummingbird,” Yang said. “Now we can see these electrons moving back and forth. When we understand how these electrons move, we can predict the material’s quantum properties and understand how to improve the performance of quantum technologies.”

The tool also characterizes materials in two other domains: energy and momentum, two important dimensions in quantum mechanics.

“This is the first time that all of these domains can be measured with great precision with one tool,” Yang said.

Creating new quantum devices

The researchers demonstrated the tool by characterizing a thin film and a topological material, but they ultimately hope to use the system to produce quantum devices such as superconducting qubits (for quantum computers) and superconducting quantum interference devices (SQUIDs), which can measure magnetic fields with great precision. That could be useful for measuring magnetic fields within topological materials or detecting magnetic quantum states within qubits.

Next they hope to continue to improve the tool’s spatial resolution and continue to break records with time resolution. They ultimately hope this new system can be a hub for work across PME and the University of Chicago, allowing other quantum researchers to develop new devices.

“This tool will build bridges across basic science and applications,” Yang said. “It gives us a lot of opportunities to crystallize innovative ideas across the school.”

Other authors on the paper include Chenhui Yan, Emanuel Green, Riku Fukumori, Nikola Protic, Seng Huat Lee, Sebastian Fernandez-Mulligan, Rahim Raja, Robin Erdakos, and Zhiqiang Mao.

Citation: “An Integrated Quantum Material Testbed with Multi-Resolution Photoemission Spectroscopy,” Yan et al, Review of Scientific Instruments, DATE. DOI: 10.1063/5.0072979

Funding: National Science Foundation, University of Chicago