Birmingham researchers reveal shape of single photon

21 Nov 2024

A new theory, explaining how light and matter interact at the quantum level, has enabled researchers to define the light particle’s precise shape.

Research at the University of Birmingham, UK, explores the nature of photons in unprecedented detail to show how they are emitted by atoms or molecules and shaped by their environment. The work is described in Physical Review Letters.

The Birmingham announcement states, “The nature of this interaction leads to infinite possibilities for light to exist and propagate, or travel, through its surrounding environment. This limitless possibility, however, makes the interactions exceptionally hard to model, and is a challenge that quantum physicists have been working to address for several decades.”

By grouping these possibilities into distinct sets, the Birmingham team has been able to produce a model that describes not only the interactions between the photon and the emitter, but also how the energy from that interaction travels into the distant “far field”. At the same time, they were able to use their calculations to produce a visualization of the photon itself.

First author Dr Benjamin Yuen, in the University’s School of Physics and Astronomy, explained, “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.”

The work is significant because it opens up new avenues of research for quantum physicists and material science. By being able to precisely define how a photon interacts with matter and with other elements of its environment, scientists can design new nanophotonic technologies that could change the way we communicate securely, detect pathogens, or control chemical reactions at a molecular level for example.

Co-author, Professor Angela Demetriadou, also at the University of Birmingham, said, “The geometry and optical properties of the environment has profound consequences for how photons are emitted, including defining the photons shape, color, and even how likely it is to exist.”

Dr Yuen, added, “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.”

PRL paper abstract

Following is the abstract from the paper in Physical Review Letters:

“We present a comprehensive second quantization scheme for radiative photonic devices. We canonically quantize the continuum of photonic eigenmodes by transforming them into a discrete set of pseudomodes that provide a complete and exact description of quantum emitters interacting with electromagnetic environments.

“This method avoids all reservoir approximations and offers new insights into quantum correlations, accurately capturing all non-Markovian dynamics. This method overcomes challenges in quantizing non-Hermitian systems and is applicable to diverse nanophotonic geometries.”