The positions of individual protons on a surface can be pinned down to within 0.1 nm, thanks to a new quantum technique based on nuclear magnetic resonance (NMR) developed by researchers in the US. The method, which works at room temperature, uses an effect that is usually considered a nuisance because it degrades the performance of diamond-based quantum bits (qubits). The researchers say that the technique could be used to study individual proteins or even spins in a superconductor.
At the heart of the new method are crystal defects that occur in diamond when two adjacent carbon atoms are replaced by a nitrogen atom and a vacant site. These "nitrogen-vacancy" (NV) centres have an electronic spin that is very well isolated from its surroundings, which means that they could play a key role in future quantum computers. And because an NV centre can emit just a single photon if excited by a laser, quantum information could be stored for long times in this kind of defect before being read out as a photon.
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