Devices that can turn on or off (like a switch) allow data to be stored. A team from the University of Chicago is working on an innovative method to achieve this, using crystals.
In a computer, data (1 or 0) is stored via transistors that alternate between two electrical states. On a CD, these 1s and 0s correspond to pits and smooth surfaces. Scientists have figured out how to use tiny imperfections, the size of an atom, in crystals to represent these 1s and 0s. Their idea could allow the equivalent of a current hard drive to be stored in a cube of material the size of a grain of sand (1 mm on each side).
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Nanophotonics, their research combines elements of quantum physics with classical techniques. By controlling defects in crystals, they define an electrically charged area as "1" and a neutral area as "0". The team uses rare earth elements like praseodymium, integrated into a crystal. These materials react to light in a precise way. An ultraviolet laser activates the system, releasing electrons that remain trapped in the crystal's defects.
Usually studied for quantum computing, these defects are here repurposed for classical storage. By mastering their electrical charge, the researchers create an ultra-miniature memory. "In a tiny little cube, there are at least a billion 'bits' of storage based on atoms," explains Tian Zhong, the project leader. This approach blends material physics and quantum technologies to rethink data storage.
A crystal glows under a UV lamp. This reaction, studied by the Zhong lab, uses properties of "rare earths".
Credit: UChicago Pritzker School of Molecular Engineering / Zhong Lab How to store data in a crystal?
The trick lies in controlling electrical charges invisible to the naked eye. When the crystal is illuminated with a UV laser, electrons are released and get trapped in imperfections (like missing atoms). These traps become "1" if they contain a charge, and "0" if they are empty. The "rare earths" make this control possible. By adjusting the color of the laser, data can be written or erased.
Unlike hard drives or USB sticks, this method allows for much higher storage density: each bit occupies the space of an atom. Even though the principle relies on quantum concepts, it is applied here to classical memories. This is an example of how fundamental science can improve everyday technologies.
Why use rare earths?
Rare earths, like praseodymium, have a unique interaction with light. They can absorb or emit specific colors (from UV to infrared), which allows them to be controlled with lasers.
In the crystal, these elements release electrons when illuminated. These electrons then fill the atomic defects, creating the 1s and 0s. The stability of rare earths ensures that data remains intact for a long time, even without electricity.
Their versatility opens the door to compact and ultra-high-performance devices. Combined with advances in nanotechnology, they could revolutionize the way we store data.