Artist’s visualization of a laser striking atoms in an optical cavity. Scientists have discovered a new phenomenon called “collectively induced transparency” (CIT) in which groups of atoms stop reflecting light at certain frequencies. The team found this effect by trapping ytterbium atoms in an optical cavity and exposing them to laser light. At certain frequencies, a window of transparency appeared through which light passed through the cavity unhindered. Credit: Ella Maru Studio
Newly Observed Effect Makes Atoms Transparent at Certain Frequencies of Light
Researchers at Caltech have discovered a new phenomenon, “collectively induced transparency” (CIT), in which light passes unhindered through groups of atoms at certain frequencies. This finding could potentially improve memory systems as a whole.
A newly discovered phenomenon called “collectively induced transparency” (CIT) causes groups of atoms to suddenly stop reflecting light at specific frequencies.
CIT was discovered by trapping ytterbium atoms inside an optical cavity—basically, a small box for light—and blasting them with a laser. Although the laser light will bounce off the atoms up to a point, as the frequency of the light is adjusted, a window of transparency appears where the light just passes through the cavity unhindered.
“We didn’t know this window of transparency existed,” said Andrei Faraon (BS ’04) of Caltech, William L. Valentine Professor of Applied Physics and Electrical Engineering, and co-author of a paper on the discovery published on April 26 in the journal Nature. “Our research has primarily been a journey to find out why.”
An analysis of the transparency window determines that it is the result of interactions in the cavity between groups of atoms and light. This phenomenon is similar to destructive interference, where waves from two or more sources can cancel each other out. Groups of atoms constantly absorb and re-emit light, which usually results in the reflection of laser light. However, at the CIT frequency, there is a balance created by the re-emitted light from each of the atoms in a group, resulting in decreased reflection.
“A group of atoms strongly coupled in the same optical field can lead to unexpected results,” said co-lead author Mi Lei, a graduate student at Caltech.
The optical resonator, which measures just 20 microns in length and includes features smaller than 1 micron, was made at the Kavli Nanoscience Institute at Caltech.
“Through conventional quantum optics measurement techniques, we found that our system reached an unexplored regime, revealing new physics,” said graduate student Rikuto Fukumori, co-lead author of paper.
Besides the transparency phenomenon, the researchers also observed that the collection of atoms can absorb and emit light from the laser either faster or slower compared to a single[{” attribute=””>atom depending on the intensity of the laser. These processes, called superradiance and subradiance, and their underlying physics are still poorly understood because of the large number of interacting quantum particles.
“We were able to monitor and control quantum mechanical light–matter interactions at nanoscale,” says co-corresponding author Joonhee Choi, a former postdoctoral scholar at Caltech who is now an assistant professor at Stanford University.
Though the research is primarily fundamental and expands our understanding of the mysterious world of quantum effects, this discovery has the potential to one day help pave the way to more efficient quantum memories in which information is stored in an ensemble of strongly coupled atoms. Faraon has also worked on creating quantum storage by manipulating the interactions of multiple vanadium atoms.
“Besides memories, these experimental systems provide important insight about developing future connections between quantum computers,” says Manuel Endres, professor of physics and Rosenberg Scholar, who is a co-author of the study.
Reference: “Many-body cavity quantum electrodynamics with driven inhomogeneous emitters” by Mi Lei, Rikuto Fukumori, Jake Rochman, Bihui Zhu, Manuel Endres, Joonhee Choi and Andrei Faraon, 26 April 2023, Nature.
DOI: 10.1038/s41586-023-05884-1
Coauthors include Bihui Zhu of the University of Oklahoma and Jake Rochman (MS ’19, PhD ’22). This research was funded by the Department of Energy, the National Science Foundation, the Gordon and Betty Moore Foundation, and the Office of Naval Research.
