Diamond nanophotonicsfor solid state quantum optics

Nathalie de Leon is a Center for Integrated Quantum Materials postdoctoral fellow in the Harvard physics department, jointly supervised by Mikhail Lukinand HongkunPark. Her research focuses on cavity QED with diamond nitrogen vacancy (NV) centers integrated with diamond-based nanophotonics, with the goal of realizing scalable solid-state quantum networks. She is also working on surface chemistry and materials characterization in diamond, as well as a variety of integrated photonic and plasmonicdevices for sensing and other applications. She received her Bachelor of Science degree in chemistry in 2004 from Stanford, where she worked under Richard Zareto detect complex organic compounds in meteoritic samples using mass spectrometry. She earned her Ph.D. in chemical physics in 2011 from Harvard in the lab of HongkunPark. Her Ph.D. research spanned several topics in device physics, including low temperature electron transport measurements in single molecule transistors, photoelectrochemicalwater splitting with nanowire electrodes, optoelectronics, and quantum plasmonics.

Large-scale quantum networks will require efficient interfaces between photons and stationary quantum bits. Nitrogen vacancy (NV) centers in diamond are a promising candidate for quantum information processing because they are optically addressable, have spin degrees of freedom with long coherence times, and as solid-state entities, can be integrated into nanophotonicdevices. An enabling feature of the NV center is its zero-phonon line (ZPL), which acts as an atom-like cycling transition that can be used for coherent optical manipulation and read-out of the spin. However, the ZPL only accounts for 3-5% of the total emission, and previously demonstrated methods of producing high densities of NV centers yield unstable ZPLs.

I will present methods and technologies for gaining both spectral and spatial control over NV emission by coupling NV centers to nanophotonicdevices. In particular, we have developed a method to create a high-density device layer of NVs with stable ZPLs in high purity diamond, and have devised a fabrication scheme to carve single mode waveguides out of the surface of the bulk diamond substrate. Using this technique, we are able to fabricate high quality factor, small mode volume photonic crystal cavities directly out of diamond, and deterministically position these photonic crystal cavities so that a stable NV center sits at the maximum electric field. We observe an enhancement of the spontaneous emission at the cavity resonance by a factor of up to 100. The NV emission is guided efficiently into a single optical mode, enabling integration with other photonic elements, as well as networks of cavities, each with their own optically addressable qubit. These nanophotonicelements in diamond will provide key building blocks for quantum information processing such as single photon transistors, enabling distribution of entanglement over quantum networks.