A light carousel spins not people but electrons. Instead of wooden horses, there are invisible blades of light. This is exactly the kind of 'carousel' physicists built to give electrons a spin.
Usually, to twist an electron beam into a vortex, you need a tiny mask — a stencil with slits carved on the atomic scale. Fabricating it is extremely challenging. The authors of this work bypassed that hurdle: they replaced the material grating with a light grating — intersecting laser beams. As an electron flies through this structure, it collides with photons (light particles) and picks up rotational momentum from them. Much like a billiard ball that starts spinning around its axis after being struck.
The main advantage of the method is flexibility. By adjusting the laser settings, you can smoothly control how strongly the electron is twisted. It's like turning a volume knob, but instead of sound, you adjust the quantum number of rotation. And crucially, the technique is universal. The same light vortices can spin protons, ions, neutral atoms, and even molecules — any particle that passes through the beams.
Such a tool will prove useful in electron microscopes, allowing samples to be examined from a new angle, and in free-electron lasers, where twisted beams can generate light with unusual properties. The light carousel has just opened, and any charged particle has a ticket.
Vortex electron beams behave like tiny magnets: their rotation creates a magnetic field along the beam, which can be used to probe materials at the atomic level.