Bing Huang

In a boron nitride crystal, the perfect atomic lattice is sometimes disrupted: an atom is missing here, or replaced by a foreign one there. Under a powerful microscope, these tiny imperfections appear as traps for electrons: they capture particles and start to emit light, and they also respond to magnetic fields.

In diamond, as in any crystal, defects are common — empty sites or foreign atoms. When they capture an electron, they can glow or become magnetic, which is valuable for quantum devices. But the electron is easily lost, and to keep it, boron has to be added to the diamond — sort of like constantly warming up an engine so it runs in the cold.