Electrically driven spin resonance in a bent disordered carbon nanotube

Resonant manipulation of carbon nanotube valley-spin qubits by an electric field is investigated theoretically. We develop a new analysis of electrically driven spin resonance exploiting fixed physical characteristics of the nanotube: a bend and inhomogeneous disorder. The spectrum is simulated for an electron valley-spin qubit coupled to a hole valley-spin qubit and an impurity electron spin, and features that coincide with a recent measurement are identified. We show that the same mechanism allows resonant control of the full four-dimensional spin-valley space.Comment: 11 pages, 7 figure

Underwater Photography of Fish Found on the Coral Reefs of Jamaica

Techniques are described for photographing fish under water at the Caribbean Biological Center near Ocha Rios, Jamaica. F-numbers 5.6 and 8 with shutter speed of 1/125 at a distance of 3 feet yielded the best photographs

Characterization of Antibiotic Resistance Profiles of Surface Water Bacteria in an Urbanizing Watershed

Wastewater treatment plants (WWTP) are typically incapable of addressing the influx of antibiotics (AB), and may act as a harbor for the selection and proliferation of antibiotic resistant bacteria (ARB). In order to examine the influence of WWTP discharge on the AB resistance profiles of surface water bacteria in an urban stream setting, E. coli isolates and total heterotrophic bacteria populations were cultivated from 6 sampling sites up and downstream of WWTPs, and evaluated for resistance to selected ABs. Samples were collected over a 9-month period in the Carter’s Creek watershed of College Station, TX. E. coli isolates were tested for resistance to ampicillin, tetracycline, sulfamethoxazole, ciprofloxacin, cephalothin, cefoperazone, gentamycin, and imipenem using the Kirby-Bauer disc diffusion method. HPCs were cultivated on R2A amended with ampicillin, ciprofloxacin, tetracycline, and sulfamethoxazole. Significant associations (p < 0.05) were observed between the locations of sampling sites relative to WWTP discharge points and the rate of E. coli isolate resistance to tetracycline, ampicillin, cefoperazone, ciprofloxacin, and sulfamethoxazole; and an increased rate of isolate multi-drug resistance. The abundance of AB-resistant HPCs was significantly greater (p < 0.05) downstream of WWTPs for all treatments; however, there was no spatially significant difference when normalized to total HPCs cultivated with no AB. Results suggest that the effects of human development, specifically the discharge of treated WWTP effluent into surface waters, are potentially significant contributors to the spread and persistence of AB resistance in the surrounding watershed

Contents

We introduce the `displacemon' electromechanical architecture that comprises a vibrating nanobeam, e.g. a carbon nanotube, flux coupled to a superconducting qubit. This platform can achieve strong and even ultrastrong coupling enabling a variety of quantum protocols. We use this system to describe a protocol for generating and measuring quantum interference between two trajectories of a nanomechanical resonator. The scheme uses a sequence of qubit manipulations and measurements to cool the resonator, apply an effective diffraction grating, and measure the resulting interference pattern. We simulate the protocol for a realistic system consisting of a vibrating carbon nanotube acting as a junction in a superconducting qubit, and we demonstrate the feasibility of generating a spatially distinct quantum superposition state of motion containing more than $10^6$ nucleons.Comment: 12 pages, 7 figure

Developing EPR Spectroscopy with 15N@C60 to Provide a Basis for Technological Solutions for a Chip-Scale Atomic Clock

The requirement for highly accurate timekeeping is increasing as technology develops in the spheres of navigation, geolocation, internet communications and financial transactions. Currently, these activities rely on a globally synchronised coordinated time which is kept precise by signals from large, laboratory based atomic clocks. However, these signals can be corrupted or jammed, and in a geopolitically uncertain environment, a reliable local alternative is required. Chip scale atomic clocks provide a portable solution, but currently available devices rely on complex vapour and laser-based technologies which are expensive, consume relatively large amounts of power and have reliability issues in microfabricated form. A chip scale device based on radio frequency EPR with endohedral fullerenes could solve complexity, cost and reliability issues provided it did not sacrifice accuracy. The work in this thesis builds upon previous experimental results, demonstrating some of the improvements required to establish the technological basis for such a clock. An improvement in resonator quality factor is shown to yield a five-fold improvement in signal to noise ratio, with which the clock transition signal of 15N@C60 is acquired more clearly than was previously possible. The low and zero field transitions of 15N@C60 are successfully mapped, yielding a precise value for the hyperfine constant and demonstrating the potential of a single resonator to respond to multiple frequencies. This offers reduced complexity for future microfabrication and provides a proof of concept for a method of field stabilisation. These results are discussed in the context of a functional clock and suggestions made for future work toward its realisation