Jonas N. Becker1,2
1Quantum Optical Devices Laboratory, Michigan State University, 567 Wilson Rd, East Lansing, MI, 48824, USA.
2Coatings and Diamond Technologies Division, Center Midwest, Fraunhofer USA

Due to its wide bandgap and low nuclear spin background, diamond is an excellent host for thousands of crystal defects with interesting optical and spin properties, only a few of which have been studied in greater detail so far. While some of these so-called color centers, such as the nitrogen vacancy or group-IV vacancy centers, have already emerged as leading candidates for quantum computing, networking and sensing, diamond holds the potential to host novel defects with potential to improve upon existing systems or to enable novel applications.
In this presentation I will introduce capabilities and challenges of established defects in diamond and provide an outlook on currently emerging centers with improved properties for quantum applications. This includes our group’s own work on nickel vacancies, which show excellent optical characteristics such as lifetime-limited linewidths in the near-infrared regime in initial experiments.
Moreover, I will discuss some of our current activities to develop a hybrid device, combining an engineered synthetic diamond substrate featuring shallow nitrogen vacancy centers nanometers below the surface with electrons trapped above a superfluid helium film on the diamond. As this noble gas surface is free of magnetic impurities, protecting the spin of individual electrons, exceptionally long spin coherence times of potentially >100s are predicted in this system. By adjusting the noble gas film thickness in conjunction with electrostatic gating, the areal density of electrons can be varied over several orders of magnitude, allowing for in-situ tunability of electron-electron interactions. Direct observation of the spatial and spin structure of this 2D electron system as well as access to and manipulation of the spin degrees of freedom of electrons in this system has been an unresolved challenge so far. Our hybrid approach promises to achieve this by employing nitrogen vacancies as optically accessible coherent spin interfaces. The resulting system will offer unprecedented functionalities for quantum computing and would be an exceptional testbed or simulator to study strongly correlated electron systems and exotic spin textures.