Almuqhim, Anas; (2019) Development of levitated electromechanics of nanodiamond in a Paul trap. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This thesis outlines the development of an experimental platform to explore recent theoretical proposals to create macroscopic spatial quantum superposition using a levitated nanodiamond containing nitrogen vacancy centres (NV). The work has demonstrated a method for electrodynamic levitation of nanodiamond and explored the feasibility and limitations of this system for experiments in macroscopic quantum mechanics. A range of electrical trap geometries were explored to determine their suitability for diamond levitation. A linear quadrupole trap was chosen and two different traps were designed, constructed and tested at atmospheric pressure and under vacuum. One trap was of a conventional linear Paul trap design, which was integrated with a microwave antenna as one of the electrodes for excitation of NV centres in the nanodiamond. A more cost effective trap was also designed and constructed from a printed circuit board. This design was easy to fabricate and had a larger numerical aperture for enhancing signal detection. Although not eventually used in this work it has found application in other levitation experiments in the laboratory. Most of the work in this thesis utilises a conventional linear Paul trap with integrated microwave excitation. The magnetic field strength and the energy density of the microwave field within the trap was modelled and were found to be suitable for excitation of NV centres. Using this trap we demonstrated optically detected magnetic resonance (ODMR) of the NV centres of diamond placed in the trap. NV fluorescence from microdiamond in this system was used to investigate the dependence of NV photoluminesence as a function of temperature, laser power and gas pressure. It was found that the temperature change not only affected the resonance frequency but also the ODMR contrast. The contrast reached its peak at about of 11.7±0.2 % at 380±35 K down to 3.2±0.2 % at 657±20 K. We demonstrated the ability to trap 100 nm diamond down to 4×10^-3 mbar and observed the NV photoluminesence at atmospheric pressure.

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