Nitrogen-Vacancy centers (NVs) have astonishing quantum properties, which make them interesting as potential hardware both for quantum computing in particular and for quantum technologies in general. In part this results from the center being protected by the diamond structure, which is at the same time very rigid and practically free from nuclear spins.

However, their properties change in unpractical ways with their proximity to the surface:

  • The closer they are to the surface, the better they interact with whatever is just beyond the surface. This is very important for quantum metrology but also in general for input/output in a quantum computing context, see for example A molecular quantum spin network controlled by a single qubit (arXiv version).
  • However, the closer the are to the surface, the more they are affected by all kinds of noise also just beyond the surface. This results from the fact that while the bulk is perfect diamond the surface is full of defects/impurities/rubbish.

My question is practical and is about cleaning and/or chemically modifying the diamond surface in order to passivate it: up to which point has this been experimentally demonstrated? What is the current state of the art, how much can quantum coherence on NV centers be improved by a detailed control of the diamond surface?


I have worked with NVs in nanodiamonds a little bit, and you are totally right, surface characteristics have a huge influence on how far we can push them. There are definitely multiple groups working on the chemistry/material science that are working to clean up the surfaces as much as possible. I had a colleague, Carlo Bradac who worked with our chemistry dept to passivate/manipulate the surface properties of nanodiamonds for us and they were way better than what we could commercially buy from anywhere. I think he has a startup now where you can order samples of nanodiamonds (and other structures) with certain properties. If I recall correctly, they did things like hot acid baths and centrifuging to do this, but as there is a startup I am not sure it is published. A place to start may be:

Influence of surface composition on the colloidal stability of ultra-small detonation nanodiamonds in biological media

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