Researchers from the University of Birmingham, UK, have developed an intriguing computer model to understand how light and matter interact. As tasks go, it is exceptionally hard, but the team was able to develop a strategy to simplify the problem. In doing so, they were also able to create something peculiar: an image representing the precise shape of a single photon.
A photon is a particle of light. Light (and matter) exists both as a particle and as a wave. This duality discovery was the solution to millennia of debate, when it became obvious from experiments that light does propagate as a wave but can also be described by distinct packets of energy, which is what we call photons.
The interaction between individual photons and matter is very important in quantum mechanics. It drives a host of different mechanisms – some of them fundamental to many technologies that we interact with every day. Understanding the interaction has been a monumental task. Light propagating through the environment has limitless possibilities for interaction.
The team took this continuous range of possibilities and simplified it by creating a discrete set. They were able to model in this way the interaction between an emitter and a photon, as well as how the photon travels into a distant “far-field”. The calculations were also able to provide a graphical understanding of the shape of a photon.
“Our calculations enabled us to convert a seemingly insolvable problem into something that can be computed. And, almost as a bi-product of the model, we were able to produce this image of a photon, something that hasn’t been seen before in physics,” first author Dr Benjamin Yuen said in a statement.
This theoretical work has applications in several fields, from physics to materials science. Technologies that require interactions between light and matter, from telecommunications to medical devices via chemical reaction control at a molecular level, can benefit from knowing how these take place.
“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,” co-author Professor Angela Demetriadou explained.
“This work helps us to increase our understanding of the energy exchange between light and matter, and secondly to better understand how light radiates into its nearby and distant surroundings. Lots of this information had previously been thought of as just ‘noise’ – but there’s so much information within it that we can now make sense of, and make use of. By understanding this, we set the foundations to be able to engineer light-matter interactions for future applications, such as better sensors, improved photovoltaic energy cells, or quantum computing,” Dr Yuen concluded.
The study is published in the journal Physical Review Letters.
