Scientists Say They've Discovered the Shape of Individual Photons

It's "something that hasn't been seen before in physics."

Everything Is Illuminated

Lighten up, people: a fascinating new paper has dropped that describes the shape of a single photon, the smallest possible form of energy in an electromagnetic field that we commonly know as light.

The work, published as a study in the journal Physical Review Letters, goes into extreme detail to predict how these quanta of light are emitted by atoms and defined by their environment. There are limitless possibilities for how those interactions could unfold, but the researchers say they've developed a practical method for predicting them.

"Our calculations enabled us to convert a seemingly insolvable problem into something that can be computed," said study lead author Benjamin Yuen, a physicist at the University of Birmingham in the UK, in a statement. "And, almost as a byproduct of the model, we were able to produce this image of a photon, something that hasn't been seen before in physics."

Shaping Up

Assigning a specific shape to a photon is a fraught task, because these massless elementary particles exhibit wave-particle duality, a curious trait of objects inhabiting the quantum realm, which is governed by spooky uncertainties.

This means that scientists think of photons as behaving like both particles and waves, depending on how they're observed. Furthermore, photons are also understood as excitations in an electromagnetic field, or like a ripple of discrete energy.

In short, they're very hard to pin down, and complicating matters further, there are infinite ways that light can interact with its surroundings and with the atoms that emit them.

But the researchers say they were able to circumvent this by reducing those possibilities into discrete sets with the help of some classical mechanics — or dividing them into "pseudomodes" — thereby streamlining how they think of the photon interactions.

Going the Distance

The advantage to modeling a photon this way, according to the researchers, is that it can accurately describe how the tiny particles travel into a distant region of the electromagnetic field surrounding an object known as the far field. Previous methods had a disconnect between the near field and far field, providing an incomplete picture of systems of light at the quantum level.

"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," said Yuen. "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."

This new understanding has very practical implications. For quantum physicists and material scientists, it could transform the development of nano-optic technology, leading to "improved photovoltaic energy cells, or quantum computing," Yuen said, and also advances in communications technology.

And let's be honest: it's also an aesthetic delight.

More on light: Scientists Intrigued by Discovery of Light That Can Cast a Shadow