Analysis of atomic magnetometry using metasurface optics for balanced polarimetry

Atomic magnetometry is one of the most sensitive field-measurement techniques for biological, geo-surveying, and navigation applications. An essential process in atomic magnetometry is measurement of optical polarization rotation of a near-resonant beam due to its interaction with atomic spins under an external magnetic field. In this work, we present the design and analysis of a silicon-metasurface-based polarization beam splitter that have been tailored for operation in a rubidium magnetometer. The metasurface polarization beam splitter operates at a wavelength of 795 nm and has a transmission efficiency > 83% and a polarization extinction ratio > 20 dB. We show that these performance specifications are compatible with magnetometer operation in miniaturized vapor cells with subpicotesla-level sensitivity and discuss the prospect of realizing compact, high-sensitivity atomic magnetometers with nanophotonic component integration

Cluster-state creation in liquid-state NMR

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2007.Includes bibliographical references (p. 57-60).The subject of this thesis is devoted to a class of multiparticle entangled states known as the cluster-states. In particular, we focused on a system of four spins and studied the entanglement properties of a four-qubit cluster-state, using a set of entanglement measures for quantifying multipartite entanglement. We then experimentally prepared the linear cluster-state in a liquid NMR sample of crotonic acid, by applying a set of pulses generated by the Gradient Ascent Pulse Engineering (GRAPE) algorithm on a temporally averaged pseudo-pure state of four carbon spins. While our spectral results were consistent with the creation of a linear cluster-state, the reconstruction of the experimental density matrix via a full state tomography of the system revealed additional challenges in the detection of certain desired spin terms. These problems must be overcome before the system could be studied quantitatively.by Jennifer T. Choy.S.B

Depth dependence of the radiative lifetime of shallow color centers in single crystalline diamond

Optically active defects in diamond are widely used as bright single-photon sources for quantum sensing, computing, and communication. For many applications, it is useful to place the emitter close to the diamond surface, where the radiative properties of the emitter are strongly modified by its dielectric environment. It is well-known that the radiative power from an electric dipole decreases as the emitter approaches an interface with a lower-index dielectric, leading to an increase in the radiative lifetime. For emitters in crystalline solids, modeling of this effect needs to take into account the crystal orientation and direction of the surface cut, which can greatly impact the emission characteristics. In this paper, we provide a framework for analyzing the emission rates of shallow (<100 nm) defects, in which optical transitions are derived from electric dipoles in a plane perpendicular to their spin axis. We present our calculations for the depth-dependent radiative lifetime for color centers in (100)-, (110)-, and (111)-cut diamond, which can be extended to other vacancy defects in diamond

Single Color Centers Implanted in Diamond Nanostructures

The development of materials processing techniques for optical diamond nanostructures containing a single color center is an important problem in quantum science and technology. In this work, we present the combination of ion implantation and top-down diamond nanofabrication in two scenarios: diamond nanopillars and diamond nanowires. The first device consists of a 'shallow' implant (~20nm) to generate Nitrogen-vacancy (NV) color centers near the top surface of the diamond crystal. Individual NV centers are then isolated mechanically by dry etching a regular array of nanopillars in the diamond surface. Photon anti-bunching measurements indicate that a high yield (>10%) of the devices contain a single NV center. The second device demonstrates 'deep' (~1\mu m) implantation of individual NV centers into pre-fabricated diamond nanowire. The high single photon flux of the nanowire geometry, combined with the low background fluorescence of the ultrapure diamond, allows us to sustain strong photon anti-bunching even at high pump powers.Comment: 20 pages, 7 figure

Plasmonic resonators for enhanced diamond NV- center single photon sources

We propose a novel source of non-classical light consisting of plasmonic aperture with single-crystal diamond containing a single Nitrogen-Vacancy (NV) color center. Theoretical calculations of optimal structures show that these devices can simultaneously enhance optical pumping by a factor of 7, spontaneous emission rates by Fp ~ 50 (Purcell factor), and offer collection efficiencies up to 40%. These excitation and collection enhancements occur over a broad range of wavelengths (~30nm), and are independently tunable with device geometry, across the excitation (~530nm) and emission (~600-800nm) spectrum of the NV center. Implementing this system with top-down techniques in bulk diamond crystals will provide a scalable architecture for a myriad of diamond NV center applications.Comment: 9 pages, 7 figure

Integrated TiO2 resonators for visible photonics

We demonstrate waveguide-coupled titanium dioxide (TiO2) racetrack resonators with loaded quality factors of 2x10^4 for the visible wavelengths. The structures were fabricated in sputtered TiO2 thin films on oxidized silicon substrates using standard top-down nanofabrication techniques, and passively probed in transmission measurements using a tunable red laser. Devices based on this material could serve as integrated optical elements as well as passive platforms for coupling to visible quantum emitters.Comment: 4 pages, 3 figure

Effects of molecular contamination and sp2^2 carbon on oxidation of (100) single-crystal diamond surfaces

The efficacy of oxygen (O) surface terminations of specific moieties and densities on diamond depends on factors such as crystallinity, roughness, and crystal orientation. Given the wide breadth of diamond-like materials and O-termination techniques, it can be difficult to discern which method would yield the highest and most consistent O coverage on a particular subset of diamond. We first review the relevant physical parameters for O-terminating single-crystalline diamond (SCD) surfaces and summarize prior oxidation work on (100) SCD. We then report on our experimental study on X-ray Photoelectron Spectroscopy (XPS) characterization of (100) diamond surfaces treated with oxidation methods that include wet chemical oxidation, photochemical oxidation with UV illumination, and steam oxidation using atomic layer deposition. We describe a rigorous XPS peak-fitting procedure for measuring the functionalization of O-terminated samples and recommend that the reporting of peak energy positions, line shapes, and full-width-half-maximum values of the individual components, along with the residuals, are important for evaluating the quality of the peak fit. Two chemical parameters on the surface, sp$^2$ C and molecular contaminants, are also crucial towards interpreting the O coverage on the diamond surface and may account for the inconsistency in prior reported values in literature