Quantum Nanophotonics with Color Centers in Diamond

Color centers in diamond are crystalline defects that share many quantum properties with single atoms. At the same time they are easier to manipulate than the latter and can be integrated into a solid state infrastructure. They are promising for realizing quantum devices such as nanoscale sensors, single-photon sources or quantum memories. Our research aims at discovering whether it is possible to draw on the promising potential of the fast developing field of nanophotonics in order to enhance or better harness the quantum properties of such systems. In particular, novel nanophotonic structures such as hyperbolic metamaterials and plasmonic waveguides are good candidates for increasing the color center's spontaneous emission rate and controlling the directionality of their emission in a broad frequency range. The broadband optical Purcell factor in plasmonic systems can be also used to control the spin readout. Conversely, the color centers' spin degree of freedom can simplify the measurement of the photonic density of states on the nanoscale. The use of CMOS-compatible epitaxially grown plasmonic materials in the design of plasmonic structures promises a new level of functionality for a variety of integrated room-temperature quantum devices based on diamond color centers.

In the scope of this project, we have examined different types of nanodiamonds and identified the characteristics that lead to optimal optical and chemical properties. We have demonstrated broadband enhancement of emission from nitrogen-vacancy (NV) center ensembles in nanodiamonds using conventional gold/alumina hyperbolic metamaterials (HMM). We have theoretically shown that planar multilayer HMM make single photon emission more directional. We have showed both the fluorescence lifetime reduction and the enhancement of single-photon emission from single NV centers in nanodiamonds coupled to an epitaxially grown CMOS-compatible HMM made of novel plasmonic materials TiN/AlScN. In our most recent work, we have studied the correlations between Purcell factor and optical measurements of NV’s spin state and the possibility to perform nanoscale sensing of photonic density of states using NV’s spin properties. Our results may enable CMOS-compatible integrated quantum devices operating at room temperature.