Inside a diamond, you sometimes find tiny flaws — a spot where a carbon atom is replaced by nitrogen, with a vacancy right next to it. Physicists call this an NV center (a nitrogen-vacancy defect). Such a defect acts like a magnetic needle that can store information in its spin. The problem is that if you pack too many of these needles together (say, a hundred in an area the size of a virus) ordinary light can no longer distinguish one from another. They blur into a single smudge.
This new work offers a way out. Each needle is gently pressed with a different force, creating microscopic strain in the crystal. As a result, each needle vibrates at its own frequency, like a string fretted at a different position. Now, by shining a laser tuned to exactly the right note, you can 'pluck' just one specific needle and read out its information. Additionally, a magnetic field that varies from point to point is applied: it allows you to control the spin of each needle individually.
The authors demonstrate how, with precisely tuned radio pulses, you can perform basic quantum operations — for example, entangling two or three such needles. Entanglement is when the state of one is instantly linked to the state of another, even if they are separated far apart. This is the key resource for a quantum computer. In the future, such dense ensembles inside diamond could become computational blocks where information is processed not sequentially but all at once — thanks to the collective dance of many magnetic needles.
NV centers in diamond glow red. When you irradiate them with a green laser, they emit a bright red glow, which is how their state is read out, like fireflies responding to a specific color.
The idea of using defects in crystals for computation is explored in Greg Egan's novel Quarantine: there, quantum processes in a diamond lattice become the key to manipulating reality.