A drop of ink falls into a glass of water, and instead of a flat stain, a ring is born that immediately starts to spin. That's roughly what the birth of a skyrmion looks like: light emitted by a tiny source twists into a stable vortex. Until now, such vortices could only be produced by large lasers. Now they've been created from single atoms right on a chip.
The secret lies in the surface on which the light source sits. It's a plate covered with rows of metal pillars tens of nanometers high — hundreds of times thinner than a human hair. Light from the atom hits the pillars and, reflecting off them, swirls like water behind a boat's stern. The vortex is so stable that it can be used as a letter in a quantum alphabet.
The authors tested the method on different sources: diamond grains with nitrogen defects. And each time they got vortices — from simple single ones to double ones resembling pretzels. This means the recipe is universal: any single emitter can be turned into a factory of quantum vortices. Such sources are needed for quantum computers, where light vortices will become carriers of information between chips.
The drop of ink in the glass has swirled, and won't stop. Likewise, a skyrmion born on a chip keeps spinning until it meets a detector. In that spin lies the future of quantum communication: dense, fast, and protected from interference.
Skyrmions are named after British physicist Tony Skyrme, who in the 1960s proposed them as a model for particles in nuclear physics. Today these vortices are found in magnets, liquid crystals, and even in the atmosphere.