Physicists Mold Giant Photons Into Custom Shapes

Image: Timothy Yeo/Centre for Quantum Technologies/National University of Singapore
Image: Timothy Yeo/Centre for Quantum Technologies/National University of Singapore
It’s hard to imagine a photon having a shape at all. For one thing, photons—pointlike, indivisible units of light—are massless, which is the whole essence of being a photon to begin with and what enables such particles to set the universe’s maximum speed limit (the c in E = mc2). How does something without mass even occupy geometric space? Alternatively, how can space be not empty yet not contain any mass?

By Michael Byrne | MOTHERBOARD

As it turns out, photons can take on different shapes and sizes and this winds up mattering a great deal when it comes to interactions between light and matter (such as atoms). To this end, researchers at the National University of Singapore have devised a method for shaping photons with extreme precision, allowing for an unprecedented look at these light-matter interactions at atomic scales.

Their work, which is described this week in Nature Communications, demonstrates that shape plays a key role in predicting whether or not an atom is likely to absorb an incoming photon, an insight likely to have consequences for the development of quantum information technologies, which hinge upon light-matter interactions.

This is among the most fundamental things in the electromagnetic world: Photons carry energy, and when a photon is absorbed by an atom, the atom takes up that energy. This might result in the atom emitting its own photons at new wavelengths (giving rise to the innate colors of objects) or otherwise displaying new properties. This interaction is what enables photosynthesis, as photons from the Sun convey energy to chloroplasts, which convert light energy into chemical energy.

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