An atom in a light trap is like a marble in a shallow pit: it jitters but doesn't jump out. The light that holds the atom also gives it a slight push, and the stronger the pushes, the harder it is to see the atom itself. For potassium-40 atoms, which are candidates for building quantum computers, these pushes have long hindered cooling and precise measurements.

In the new work, a solution was found: a wavelength of light at which the pushes vanish. It's called 'magic'—as if the pit became perfectly smooth and the marble stopped jittering. For potassium-40, this wavelength is 1227.54 nanometers, slightly longer than the red light the eye can see. The scientists tested this wavelength in a real trap made of a laser beam and confirmed that the atoms behave calmly, just as calculations predicted.

This discovery paves the way for large lattices of cold potassium-40 atoms. They can be used to simulate complex materials and possibly build quantum computers. Atoms in such lattices will lie neatly, like beads on a string, and can be manipulated for long periods with high precision.