Physicists used ‘dark photons’ in an effort to rewrite physics in 2025

A fundamental tenet of quantum theory was put in jeopardy this year when a team of researchers proposed a radically new interpretation of an experiment on the nature of light.

Central to this new work was the double-slit experiment, first conducted in 1801 by physicist Thomas Young, who used it to confirm that light acts like a wave. Classically, something that is a particle can never also be a wave, and vice versa, but in the quantum realm the two are not mutually exclusive. In fact, all quantum objects exhibit what is called wave-particle duality.

For decades, light seemed to be an excellent example: experiments showed that it sometimes behaves like a particle called a photon, sometimes like a wave producing effects similar to those observed by Young. But earlier this year, Celso Villas-Boas of the Federal University of São Carlos in Brazil and his colleagues proposed an interpretation of the double-slit experiment that involves only photons, eliminating the need for the wavy part of the duality of light.

After New scientist After reporting on the study, the team behind it was contacted by many colleagues interested in the work, which has since been widely cited, Villas-Boas says. A YouTube video about it has been viewed more than 700,000 times. “I have been invited to give lectures on this subject in Japan, in Spain, here in Brazil and in many places,” he says.

In the classic double-slit experiment, an opaque barrier with two adjacent narrow slits is placed between a screen and a light source. Light passes through the slits and falls on the screen, which consequently has a pattern of light and dark vertical stripes, known as classic interference. This is usually because the light waves propagate through the two slits and crash into each other at the screen.

Researchers abandoned this picture and turned to so-called dark states of photons, special quantum states that do not light up the screen because they are incapable of interacting with any other particles. These states explained the dark stripes, it was no longer necessary to invoke light waves.

This is a notable departure from the most common view of light in quantum physics. “Many teachers told me: ‘You’re touching on one of the most fundamental things in my life, I’ve been teaching interference by book since the beginning, and now you’re saying that everything I taught is wrong,’” Villas-Boas says. He says some of his colleagues have accepted the new point of view. Others remained, if not outright skeptical, at least cautiously intrigued, like New scientistThe reports were confirmed when the study was first made public.

Since then, Villas-Boas has been busy examining several new implications of the dark states of photons. For example, his and his colleagues’ mathematical analysis revealed that thermal radiation, such as light from the sun or stars, can have dark states that carry a significant portion of its energy, but because they do not interact with other objects, this energy is, in some sense, hidden. This could be tested in experiments placing atoms in cavities where their interactions with light can be precisely monitored, Villas-Boas says.

He says his team’s reinterpretation of interference also allows us to understand seemingly impossible phenomena, like waves interfering even when they don’t directly overlap or the interference between mechanical and electromagnetic waves. In both cases, abandoning the wave model in favor of light and dark photonic states opens new possibilities. Villas-Boas can even imagine using some of these findings to build new types of switches or light-operated devices that are only transparent to certain types of light.

According to him, all this work relates to a fundamental truth of quantum physics: it is impossible to discuss quantum objects without describing how they interact with detectors and other measuring devices, including their darkness. “This is not new, in my opinion. This is what quantum mechanics already tells us,” explains Villas-Boas.