Engineering nano-scale diamond quantum devices and their applications to neuroscience.
Creators: name: Hanlon, Liam
Publisher: name: The Australian National University
Year: 2022

description: As modern neuroscience improves, our understanding of neuronal systems and the human brain improves as well. This includes practical understanding of neurological diseases and how to treat them as well as a more general understanding of how humans and animals think and understand the world around them. One key mechanism for understanding neuronal systems is in experimental measurements. Being able to sense the electromagnetic signalling system that neurons produce in a network is essential for understanding their function; so much so that a lack of useful means of measuring neuron signals severely limits any new information neuroscience research can provide. Measuring and imaging neuronal signals however can be a difficult process, when measuring signals there is a requirement for a highly sensitive device which can measure the smallest electromagnetic signal of a neuron at particular regions of the cell as well as across a dense neuron network. Furthermore, measurements must be performed in such a way as to not alter the normal function of the cell. Whilst many technologies for measuring and imaging neuron networks exist, they all have distinct advantages and disadvantages that limits their effectiveness or applicability. The nitrogen-vacancy (NV) center is an atomic defect in a diamond lattice whose unique quantum properties gives the defect great potential to be an extremely sensitive device for measuring electromagnetic signals. Coupled with its placement in the biocompatible diamond lattice, the NV center can potentially be used as a novel sensor of neuron signals in a way that would be vastly superior to current technologies. However there are issues with design implementations which limits the potential benefits of the NV as a neuro-sensor. In this thesis, a detailed exploration of the NV as a neuro-sensor is undertaken including a unique approach which places the defects in an array of diamond nano-pillars to improve the capacity to sense neuron signals at specific locations. In this study, the anatomy and physiology of the neuron is outlined and the current state of neuron imaging is presented including the role NV neurosensing would play in the field. The capacity of NV neurosensing is assessed with detailed theoretical modelling as well as a proof-of-principle growth study of neurons on an array of diamond nano-pillars. The results of the growth study and modelling suggest that the NV would be inappropriate as a magnetic field sensor, but would be useful as an electric field sensor for neuronal systems. Whilst further study of the NV in its capacity as a neuro-sensor is required, the results motivate a more general study of the NV and the various means that can improve its performance. This general approach allows for further consideration of the NV as a sensor for non-biological applications as well as a qubit for quantum computing and networking applications. As all the quantum operations in sensing and computing rely on the same spin-dependent dynamics of the NV itself, any improvement to NV performance can improve the NV viability in a number of fields including, but not exclusive to neuro-sensing.