Crystal Memory Stores Terabytes of Data

Revolutionizing Memory Storage with Crystal Defects

Researchers at the University of Chicago Pritzker School of Molecular Engineering (UChicago PME) have made a significant breakthrough in the field of classical computer memory applications. By exploring a technique to create ones and zeroes out of crystal defects, each the size of an individual atom, they have paved the way for groundbreaking microelectronic memory storage.

The result of an interdisciplinary approach, this innovation leverages quantum techniques to transform research on radiation dosimeters into a novel method for memory storage. According to UChicago PME Assistant Professor Tian Zhong, "Each memory cell is a single missing atom — a single defect. Now you can pack terabytes of bits within a small cube of material that's only a millimeter in size."

First author Leonardo França, a postdoctoral researcher in Zhong's lab, explained, "We found a way to integrate solid-state physics applied to radiation dosimetry with a research group that works strongly in quantum, although our work is not exactly quantum. There is a demand for people who are researching quantum systems, but at the same time, there is a demand for improving the storage capacity of classical non-volatile memories. And it's on this interface between quantum and optical data storage where our work is grounded."

França's journey began during his PhD research at the University of São Paulo in Brazil, where he was studying radiation dosimeters. He highlighted the importance of monitoring radiation doses in environments such as hospitals and particle accelerators, where materials can absorb radiation and store that information for a certain period of time.

Through optical techniques, França was able to manipulate and "read" the stored information by shining light on the crystal. He explained, "When the crystal absorbs sufficient energy, it releases electrons and holes, which are captured by the defects. We can read that information by releasing the electrons and using optical means to interpret it."

Recognizing the potential for memory storage, França brought this non-quantum work into Zhong's quantum laboratory to leverage quantum techniques for building classical memories. The memory storage technique utilizes "rare earth" ions, specifically a rare-earth element called Praseodymium and a Yttrium oxide crystal, showcasing the powerful optical properties of rare earths.

"It's well known that rare earths present specific electronic transitions that allow you to choose specific laser excitation wavelengths for optical control," França noted. Unlike dosimeters, which are activated by X-rays or gamma rays, the crystal memory storage device is activated using a simple ultraviolet laser that stimulates the lanthanides to release electrons, which are then trapped by defects in the oxide crystal.

While crystal defects are commonly used in quantum research to create "qubits," the UChicago PME team has found a new application by guiding when defects are charged and which ones are not. By assigning a charged gap as "one" and an uncharged gap as "zero," they have effectively transformed the crystal into a high-capacity memory storage device.

Within a millimeter cube, the researchers have demonstrated the presence of at least a billion classical memories based on atoms. This groundbreaking work opens up new possibilities for memory storage technologies and showcases the potential of integrating quantum techniques into classical applications.

Image: A crystal used in the study charges under UV light. The process created by the University of Chicago Pritzker School of Molecular Engineering Zhong Lab could be used with various materials, taking advantage of rare earth's powerful, flexible optical properties. Credit: UChicago Pritzker School of Molecular Engineering — Zhong Lab.

Paper: "All-optical control of charge-trapping defects in rare-earth doped oxides," França et al, Nanophotonics, February 14, 2025. DOI: https://doi.org/10.1515/nanoph-2024-0635.

Funding: This work was supported by the U.S. Department of Energy, Office of Science, for support of microelectronics research, under Contract No. DE-AC0206CH11357.