Quantum research paves the way for efficient, ultra-high-density optical memory storage

As our digital world generates massive amounts of data (more than 2 quintillion bytes of new content every day), yesterday’s storage technologies are quickly reaching their limits. Optical memory devices, which use light to read and write data, offer the potential for durable, fast, and energy-efficient storage.

Now, researchers at the U.S. Department of Energy’s (DOE) Argonne National Laboratory and the University of Chicago’s Pritzker School of Molecular Engineering (PME) have proposed a new type of memory, in which Optical data is transferred from a rare earth element embedded in a solid material to a nearby quantum defect. Their analysis of how such technology could work is published in Physical examination research.

“We discovered the basic physics of how energy transfer between defects could be the basis of an incredibly efficient optical storage method,” said Giulia Galli, Argonne principal scientist and Liew Family Professor at SMEs. “This research illustrates the importance of exploring first principles and theories of quantum mechanics to inform new and emerging technologies.”

Most optical memory storage methods developed in the past, including CDs and DVDs, are limited by the diffraction limit of light. A single data point cannot be smaller than the wavelength of the laser that writes and reads the data. In their new work, the researchers proposed increasing the binary density of optical storage by integrating numerous rare earth emitters into the material. Using slightly different wavelengths of light – an approach known as wavelength multiplexing – they hypothesized that these transmitters could fit more data into the same area.

To show the feasibility of this approach, Galli and his colleagues first studied the physical requirements needed for efficient and dense optical storage. They created models of a theoretical material interspersed with atoms of narrow-band rare earth emitters. These atoms absorb light and re-emit it at specific, narrow wavelengths. The researchers showed how this narrow wavelength light could then be captured by a nearby quantum defect.

The study’s predictions were obtained by combining basic theories of electronic structure to map defect absorption states, with theories of quantum mechanics to model the propagation of light at the nanoscale. By developing such new theoretical models, the team was able to better understand the rules governing how energy is moved between emitters and defects, as well as how defects store captured energy.

“We wanted to develop the theory needed to predict how energy transfer between emitters and defects works,” said Swarnabha Chattaraj, a postdoctoral researcher at Argonne. “This theory then allowed us to determine the design rules for potentially developing new optical memories.”

Although scientists have a good understanding of how quantum defects in a solid material typically interact with light, they had not previously studied how their behavior changes when light comes from an incredibly close source, such as rare earth emitters. narrowband integrated just one to a few nanometers.

“This type of near-field energy transfer is thought to follow different symmetry rules than more commonly known far-field processes,” said Supratik Guha, senior advisor at the Directorate of Physical Sciences and Engineering. d’Argonne and professor at PME.

Indeed, the group discovered that when quantum defects absorbed the narrow band of energy from nearby atoms, not only were they excited from their ground state, but they also inverted their spin state. This spin state transition is difficult to reverse, suggesting that these defects could store data for long periods of time. Additionally, due to the smaller wavelengths of light emitted by narrow-band rare earth emitters, as well as the small size of the defects, the system could provide a denser method of data storage than others optical approaches.

“To begin to apply this to the development of optical memory, we still need to answer additional fundamental questions about how long this excited state persists and how we read the data,” Chattaraj said. “But understanding this process of near-field energy transfer is an important first step.”