Diamond nanophotonic devices for quantum information processing and sensing
Massachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
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The nitrogen vacancy (NV) center in diamond has in recent years emerged as a promising solid state system for quantum information processing and sensing applications. However, using NV centers to build up quantum networks for these applications faces several challenges, such as the lack of efficient interface between NVs and photons, difficulty of maintaining spin coherence times, and scalable techniques for fabrication of NV-photon networks. This thesis focuses on overcoming these challenges by fabricating diamond devices to improve the collection efficiency of NV photon emission, especially from the zero phonon line (ZPL), while maintaining long spin coherence times after fabrication. After an introduction to the subject matter in Chapter 1, Chapter 2 discusses a fabrication technique to produce vertical membranes out of bulk diamond plates. This work showed that after reactive ion etching, the spin properties of isolated NVs in diamond nanostructures were largely preserved. We also observed increased photoluminescence collection from shallow implanted NV centers in these slabs. In Chapter 3, we describe a versatile nanofabrication method based on re-usable silicon membrane hard masks, patterned using standard lithography and mature silicon processing technology. These masks are transferred precisely onto targeted regions of diamond membranes, where photonic devices can be realized without the need for spin coating, wet etching or electron beam exposure. Chapter 4 describes and demonstrates an alternative technique for fabricating one-dimensional photonic crystal (PC) cavities in single-crystal diamond by a combination of reactive ion etching (RIE) and focused ion beam milling. We compare it to transferred silicon hard mask lithography with RIE. Chapter 5 demonstrate NV-nanocavity systems in the strong Purcell regime with consistently high Q factors while preserving the long spin coherence times of NVs. These systems enable coherent spin control of cavity-coupled semiconductor qubits with coherence times exceeding 200 [mu]s - an increase by two orders of magnitude over previously reported optical cavity-coupled solid-state qubits. Chapter 6 introduces a circular diamond "bullseye" grating that achieves the highest reported photon collection rate from a single NV center of 4.56 0.08 Mcps at saturation when fitted with the widely-used background counts subtraction method. We also quantified the emission by a g(²)-corrected saturation curve measurement which gives a rigorous single photon count rate of 2.7 ± 0.09 Mcps. By using dynamical decoupling sequences, we measured a spin coherence time of 1.7 ± 0.1 ms, which is comparable to the highest reported spin coherence times of NVs under ambient conditions and also indicates that the bullseye fabrication process does not degrade the spin properties noticeably. The planar architecture allows for on-chip integration, and the circular symmetry supports left- and right-handed circularly polarized light for spin-photon entanglement. In Chapter 7, we demonstrate a top-down fabrication process using a porous metal mask and a self-guiding RIE process that enables rapid nanocrystal creation across the entirety of a high-quality chemical vapor deposited (CVD) diamond substrate. High-purity CVD nanocrystals produced in this manner exhibit single NV phase coherence times reaching 210 ps and magnetic field sensitivities of 290 nT.Hz⁻¹/² without compromising the spatial resolution of a nanoscale probe.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.Cataloged from PDF version of thesis.Includes bibliographical references (pages 107-123).
DepartmentMassachusetts Institute of Technology. Department of Electrical Engineering and Computer Science.
Massachusetts Institute of Technology
Electrical Engineering and Computer Science.