Scanning electron microscope image of the device used to extract ZPL photons from a diamond NV centre. The waveguide – with a diffraction grating at either end – is below the ring of diamond. (Courtesy: Andrei Faraon)

Physicists extract photons from diamond ring

Feb 8, 2013

Physicists in the US are the first to make an integrated device that extracts photons from a tiny piece of diamond before the light is sent through a waveguide to the outside world. The photons all have the same frequency and originate in a nitrogen vacancy (NV), which is a defect that occurs in diamond when two neighbouring carbon atoms are replaced by a nitrogen atom and an empty lattice site. According to the researchers, the chip could be used to create quantum-information technology such as quantum repeaters.

For anyone trying to build a quantum computer NVs are useful because they have an electronic spin that is extremely well isolated from the surrounding lattice – so if an NV is placed in a certain spin state then it will remain in that state for ages, even at room temperature. An NV can also emit just a single photon if excited by a laser of the right wavelength. Taken together, these properties mean that NVs allow data to be stored for long times in a defect, before being read out as a single photon.

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