Scientists crack the atomic code behind single-photon quantum emitters

Scientists have made a significant breakthrough in understanding and controlling single-photon quantum emitters—tiny atomic-scale light sources critical for future quantum technologies such as quantum computing, secure communications, and sensitive sensors. These quantum emitters release light one photon at a time, but their atomic origins were previously difficult to observe and link directly to their optical behavior. Researchers at Argonne National Laboratory overcame this challenge by using a novel instrument called QuEEN-M, which combines atomic-resolution imaging with cathodoluminescence spectroscopy. This allowed them to simultaneously identify the exact atomic defects in ultrathin hexagonal boron nitride crystals responsible for single-photon emission. The team discovered that twisting layers of hexagonal boron nitride at specific angles created “twisted interfaces” that enhanced the light emission signal by up to 120 times, enabling localization of emitters with nanometer precision. They identified the atomic structure of a blue quantum emitter as a carbon dimer—two vertically stacked carbon atoms within the crystal lattice.