Imagine a light switch so small it is made from just a few atoms, and so precise it releases light one particle at a time. 

These tiny switches, called quantum emitters, are considered one of the core components for future technologies such as quantum computers, ultra-secure communication networks, and extremely sensitive sensors. 

For years, scientists have struggled to fully understand and control them, but this won’t be the case for long. In a recent study, researchers in the US shed light on the process of identifying, designing, and placing single-photon sources with atomic precision inside ultrathin materials. 

This achievement removes one of the biggest roadblocks in quantum materials science and brings practical quantum devices much closer to reality.

The quantum emitter enigma

Quantum emitters work by releasing single photons, individual packets of light, on demand. This ability is critical because quantum technologies rely on absolute control over light and information. 

The problem has always been visibility and control. The exact atomic defects responsible for these emitters are incredibly small and difficult to observe. Scientists could either study how they emit light or examine their atomic structure—but not both at the same time. 

“The challenge in studying quantum emitters is that their optical behavior is determined by their atomic structure, which is very hard to observe directly,” Jianguo Wen, one of the study’s authors and a material scientist at the Argonne National Laboratory, said.

This fundamental limitation has long kept quantum emitters mysterious and hard to engineer. However, the new research finally overcomes this tradeoff using a smart approach. 

Solving the problem atom by atom

The study authors focused on hexagonal boron nitride, an ultrathin, two-dimensional crystal that is only a few atoms thick and already known to host quantum emitters.

They used a powerful custom-built instrument called QuEEN-M (Quantum Emitter Electron Nanomaterial Microscope). This advanced microscope combines atomic-scale imaging with a technique known as cathodoluminescence (CL) spectroscopy. 

In simple terms, the researchers fired a tightly focused beam of electrons at the material. When the electrons hit a defect in the crystal, that defect emits light. By studying the color and brightness of the emitted light, scientists could learn exactly which atomic structures were responsible. 

This approach solved a long-standing problem. Normally, studying light emission requires thicker samples, while studying atomic structure needs extremely thin ones. QuEEN-M allowed the researchers to do both at once, linking light emission directly to specific atomic defects. 

This is not it, the researchers made another crucial discovery: twisting layers of hexagonal boron nitride at specific angles created special “twisted interfaces” that dramatically boosted the light signal from quantum emitters—sometimes by as much as 120 times. 

This stronger signal made it possible to locate emitters with extraordinary accuracy, down to less than 10 nanometers. Using this enhanced precision, the researchers identified the atomic structure of a blue quantum emitter. It turned out to be a carbon dimer, two carbon atoms stacked vertically inside the crystal. 

Moreover, “once we could connect the atomic structure with the light it gives off, it opened the door to precise engineering of these quantum emitters. (This means) we can now create and adjust them on demand using an electron beam,” Thomas Gage, one of the study authors and a scientist at Argonne, said.

A big quantum leap

This work marks a major shift from simply discovering quantum emitters to engineering them with intention. This is because being able to place single-photon sources exactly where needed is essential for building scalable quantum devices. 

Moreover, chips that rely on precisely positioned quantum emitters could process information more efficiently, transmit data securely, and amplify signals with minimal loss.

However, despite the advances, there are challenges that remain. The technique currently relies on highly specialized microscopes, which limits immediate large-scale manufacturing. 

Future research will focus on making these methods more scalable and exploring how different atomic structures affect photon behavior.

The study is published in the journal Advanced Materials.