This study is presented in nine chapters as follows: Chapter one reviews the reported literature on the NMR of natural diamond. The NMR signal of diamond consists on a single line at 39 ppm from TMS and two hyperfine lines due to 13C interactions. The reported relaxation times, measured in natural diamond, synthetic diamonds and 13C enriched diamonds, are discussed. The second chapter introduces the apparatus used, which included a Bruker Avance NMR spectrometer, a Bruker ESP380E pulsed EPR spectrometer and a high powersband DNP system. The availability of this excellently equiped laboratory presented a unique opportunity to perform this investigation. Chapter three outlines the experimental techniques used as well as the manner in which the acquired data was processed. The fourth chapter presents an overview of the most common defects found in diamond. Proposed models of these defects are presented and the resulting EPR spectra displayed. The methods developed to determine the paramagnetic impurity concentration from the EPR line width and the spin-spin relaxation times are presented in the fifth chapter. The line width gives the total paramagnetic impurity concentration to about 10 ppm. The spin-spin relaxation time allows the determination of Pl and P2 paramagnetic impurity concentrations individually, to much lower levels from measurements on the central and hyperfine lines. This information was used in the explanation of the relaxation behaviour for the various diamonds investigated. The temperature dependence of the paramagnetic electron relaxation times is reported in the sixth chapter. The results obtained are consistent with the findings in prior work that Pl impurities are typical Jahn Teller centres. Two diamonds, however, display trends that depart from this theory. These diamonds contain N3 defect centres, which appear to be responsible for this behaviour. It was found in these experiments that, bar thermal expansion effects, the spin-spin relaxation time is essentially independent of temperature. The seventh chapter deals with the solid state and thermal mixing effects. The relevant theory, results obtained and a discussion of these results, are presented. The effect of impurity concentration, defect types, microwave power, the exposure time and the offset from resonance on the polarisation rates and the 13C polarisation are investigated in depth. Finally the effect of applying the DNP treatment on the central and hyperfine lines is discussed. The pulsed DNP process is presented in the eighth chapter. The relevant theory, the effects of matching of the Hartmann-Hahn condition, impurity concentrations and types, on the polarisation rate and signal enhancement of JJC nuclei is given. A comparison to the continuous wave techniques is then made. The ninth chapter summarises the achievements and recommendations for further work. / Physics / D. Phil. (Physics)

This study is presented in nine chapters as follows: Chapter one reviews the reported literature on the NMR of natural diamond. The NMR signal of diamond consists on a single line at 39 ppm from TMS and two hyperfine lines due to 13C interactions. The reported relaxation times, measured in natural diamond, synthetic diamonds and 13C enriched diamonds, are discussed. The second chapter introduces the apparatus used, which included a Bruker Avance NMR spectrometer, a Bruker ESP380E pulsed EPR spectrometer and a high powersband DNP system. The availability of this excellently equiped laboratory presented a unique opportunity to perform this investigation. Chapter three outlines the experimental techniques used as well as the manner in which the acquired data was processed. The fourth chapter presents an overview of the most common defects found in diamond. Proposed models of these defects are presented and the resulting EPR spectra displayed. The methods developed to determine the paramagnetic impurity concentration from the EPR line width and the spin-spin relaxation times are presented in the fifth chapter. The line width gives the total paramagnetic impurity concentration to about 10 ppm. The spin-spin relaxation time allows the determination of Pl and P2 paramagnetic impurity concentrations individually, to much lower levels from measurements on the central and hyperfine lines. This information was used in the explanation of the relaxation behaviour for the various diamonds investigated. The temperature dependence of the paramagnetic electron relaxation times is reported in the sixth chapter. The results obtained are consistent with the findings in prior work that Pl impurities are typical Jahn Teller centres. Two diamonds, however, display trends that depart from this theory. These diamonds contain N3 defect centres, which appear to be responsible for this behaviour. It was found in these experiments that, bar thermal expansion effects, the spin-spin relaxation time is essentially independent of temperature. The seventh chapter deals with the solid state and thermal mixing effects. The relevant theory, results obtained and a discussion of these results, are presented. The effect of impurity concentration, defect types, microwave power, the exposure time and the offset from resonance on the polarisation rates and the 13C polarisation are investigated in depth. Finally the effect of applying the DNP treatment on the central and hyperfine lines is discussed. The pulsed DNP process is presented in the eighth chapter. The relevant theory, the effects of matching of the Hartmann-Hahn condition, impurity concentrations and types, on the polarisation rate and signal enhancement of JJC nuclei is given. A comparison to the continuous wave techniques is then made. The ninth chapter summarises the achievements and recommendations for further work. / Physics / D. Phil. (Physics)

L'exploration du monde quantique au moyen d'objets macroscopiques constitue l'un des défis centraux de ces dernières décennies pour la recherche en physique. Parmi les systèmes proposés pour atteindre cet objectif, les systèmes hybrides, qui couplent un résonateur nanomécanique à un qubit unique, font figure de paradigme.L'excitation cohérente d'un oscillateur mécanique macroscopique par un unique spin électronique ouvrirait en particulier de nouvelles perspectives pour la création d'états quantiques arbitraires du mouvement.Dans ce manuscrit, nous considérons un système hybride constitué d'un oscillateur nanomécanique et du spin électronique d'un unique centre NV, couplés entre eux par une interaction magnétique. Nous nous concentrons sur le cas d'une interaction paramétrique où la vibration mécanique module l'énergie du qubit, et plus précisément sur le cas où le qubit ainsi forcé et l'oscillateur mécanique évoluent sur des échelles de temps comparables.Dans cette situation, nos observations montrent une synchronisation de la dynamique du qubit sur l'oscillation mécanique. Le phénomène est dans un premier temps abordé par une expérience-test qui remplace le mouvement mécanique par un champ radiofréquence en couplage paramétrique avec le spin. Cette première implémentation permet de dégager les propriétés essentielles de l'effet paramétrique, qui est dans un second temps observé sur l'expérience principale.Dans cette seconde expérience, un centre NV est attaché à l'extrémité d'un nanofil de carbure de silicium en vibration placé dans un fort gradient de champ magnétique. Le caractère bidimensionnel des déformations du nanofil octroie alors à la synchronisation des signatures vectorielles encore inédites, qui peuvent aussi être interprétées comme la manifestation d'un triplet de Mollow phononique, ainsi qu'il a été observé dans les premières expériences d'électrodynamique quantique.Finalement, nous explorons la robustesse de la synchronisation vis-à-vis du mouvement Brownien du résonateur, et démontrons la possibilité de protéger le qubit de cette source de décohérence additionnelle grâce à une excitation mécanique de faible amplitude. / Probing the quantum world with macroscopic objects has been a core challenge for research in physics during the past decades. Proposed systems to reach this goal include hybrid devices that couple a nanomechanical resonator to a single spin qubit. In particular, the coherent actuation of a macroscopic mechanical oscillator by a single electronic spin would open perspectives in the creation of arbitrary quantum states of motion.In this manuscript, we investigate a hybrid system coupling a nanomechanical oscillator and a single electronic spin of a NV defect in magnetic interaction. We focus on the parametric interaction case, when the mechanical motion modulates the qubit energy, and in particular when the driven qubit and mechanical oscillators evolves on similar timescales. In that situation a synchronization of the qubit dynamics onto the mechanical motion is observed. The phenomenon is first explored on a test experiment where mechanical motion is replaced by a parametrically coupled RF field. It allows to establish the main properties of the phenomenon, which is subsequently investigated on the core experiment. It consists of a NV defect attached at the vibrating extremity of a silicon carbide nanowire, immersed in a strong magnetic field gradient. The bidimensional character of the nanowire deformations is responsible for novel vectorial signatures in the synchronization, which can also be viewed as a phononic Mollow triplet as observed in early quantum electrodynamics experiments. We finally explore the robustness of the synchronization against the Brownian motion of the resonator and demonstrate the possibility to protect the qubit against this additional decoherence source by applying a small coherent mechanical drive.