A laser pulse enters a gas and pushes electrons aside, leaving behind a bubble—an empty region that travels through the plasma at nearly the speed of light. An electron that finds itself inside this bubble is accelerated like a surfer on a wave crest. Usually, this acceleration is described simply: the particle just goes faster and faster, and that's it. But electrons have quantum properties, and one of them is the twist of their wave.

The scientists calculated that the bubble not only accelerates the electron but also maintains its twist. Inside the bubble, the electron's transverse motion is restricted to certain modes—like a string that can only vibrate at its natural frequencies. The longitudinal field of the bubble pushes the electron forward without destroying this twist. The key is that the electron must not stray too far from the bubble's axis. Then the vortex can survive even at enormous energies. Previously, it was unclear whether a twisted electron could be accelerated without being destroyed. Now it's clear: it can, provided you use a plasma bubble of the right shape. This opens the door to creating beams of twisted electrons for future experiments.