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A new theory, that explains how light and matter interact at the quantum level has enabled researchers to define for the first time the precise shape of a single photon. Credit: Dr Benjamin Yuen.

Understanding these fundamental aspects of photon-matter interactions could open up new possibilities in quantum physics and material science. It could pave the way for new and improved nanophotonic technologies, pathogen detection or controlled chemical reactions.

The research is published in the Physical Review Letters.

“The geometry of the environment defines a photon’s interaction with matter,” the authors write.

“The geometry and optical properties of the environment has profound consequences for how photons are emitted, including defining the photons shape, colour, and even how likely it is to exist,” adds co-author Angela Demetriadou.

The researchers from the University of Birmingham explored how photons are emitted by atoms or molecules and are shaped by their environment.

They produced a theoretical model which groups into distinct sets the infinite possibilities of how light can interact. The model describes the interactions between the photon and its source, as well as how the energy from the interaction travels into the distance.

Photons are quantum mechanical objects – that is they can be described as both waves or as particles. Neither description by itself fully captures all the characteristics of photons and other fundamental particles.

This wave-particle duality has made it hard to pin down the exact shape of individual subatomic particles.

“Our calculations enabled us to convert a seemingly insolvable problem into something that can be computed,” says first author Benjamin Yuen. “And, almost as a by-product of the model, we were able to produce this image of a photon, something that hasn’t been seen before in physics.”[…]

Source: The shape of a photon, particle of light: “something that hasn’t been seen before in physics”