Diamond Materials

Diamond Materials for Quantum Application

23. September 2014: The DFG research group FOR 1493 “Diamond Materials and Quantum Applications” goes into its second funding period. FOR1493 is a national research consortium funded by the Deutsche Forsch-ungsgemeinschaft.

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ERC Advanced Grant


Quantum spintronics with diamond spins

Synthetic quantum systems being made up from spins promise to be particularly robust and easy to control. This is particularly true for spins in carbon materials especially diamond. Low spin-orbit and spin phonon interaction lead to particularly long-lived spin coherence times for electron spin in diamond reaching ms under ambient conditions. Among the more than 100 luminescent defects in diamond there are a wealth of electron paramagnetic impurities and among those a set do allow for an optical read out of spin states. Most notably this is the case for the nitrogen vacancy center. This defect comprising a nitrogen atom with a neighboring vacancy shows strongly allowed optical transitions allowing for single center detection. Electronic ground as well as optically excited state are spin triplets. Spin orbit coupling results in a spin state selective fluorescence intensity which is the basis for spin state readout. Meanwhile there are detailed calculations on the precise level structure and measurements on the rates among levels available.

The diamond spin defect turns out to be a surprisingly versatile and well controllable solid state quantum system. On the one hand long relaxation and coherence times guarantee excellent single spin control. On the other hand in high purity diamond material only few spin impurities interact with the defect spin forming an almost text book example for a “central spin” system.
Scaling diamond defects to large scale quantum systems is an outstanding challenge in the field. Different attempts are underway to increase the complexity from single spin to spin arrays. Exploiting e.g. ground state paramagnetic moments for mutual spin coupling requires positioning of defects with few nanometer precision, an outstanding challenge for material and implantation science.

Few photonic or plasmonic structures with coupled diamond defects are available so far. Moderate coupling of defect photons to photonic or plasmonic structures has been achieved. In particular producing solid state photonic cavities from diamond is a remaining task. Once again the spin level structure of the nitrogen-vacancy defect has led to the observation of spin-photon entanglement, a unique observation for solid state systems so far.