Large Mass Interferometry for Understanding and Measuring Aspects of Gravity

This thesis presents my work on exploring the use of large mass Stern-Gerlach interferometry for measuring both classical and quantum mechanical aspects of gravity. Chapter 1 serves as an introduction of the background physics necessary to understand this thesis. Part I (Chapters 2 and 3) is concerned with the underlying quantum mechanical mechanism behind a previously proposed experiment aimed at evidencing the quantum nature of gravity by witnessing gravitationally mediated entanglement. This includes determining the assumptions which must hold for a conclusion to be drawn from a positive result of the experiment and providing a clear and intuitive understanding behind what can and what can not be proved by such an experiment. Finally, this section presents the work done to explore further how entanglement forms in gravitationally interacting quantum systems. Part II of this thesis (Chapters4 and 5) discusses how a large mass interferometer will couple to the space-time metric for use as a detector. This includes considering the basic design of such a device, how different components of the space-time metric can be identified individually and an initial exploration of the final sensitivity of such a device given realistic noise parameters. Part III (Chapter 6) of this thesis looks at how such devices may be implemented experimentally, building off previous designs to create a large mass, large spatial superpositions with sufficient coherence to enable their use for interferometry. This is done to specifically design the interferometer around some issues and limitations with large mass interferometry using the Stern-Gerlach effect which have not been considered elsewhere

Use of Medicines by Community Dwelling Elderly in Ontario

OBJECTIVE: Prescription medicine use by the elderly is of growing concern as indicated by a large literature focused on rising costs, patient compliance and the appropriateness of use. However, prescriptions account for only a portion of medicines used by the elderly, who have increasing access to non-prescription medicines and natural health products. The objective of this paper is to describe overall medicine use among the elderly in Ontario. METHODS: Using the National Population Health Survey (1996/97), we describe self-reported use of prescription, non-prescription and alternative medicines among elderly Ontarians aged 65+, and we compare use among four age sub-groups and by gender. Analysis is focused on the prevalence of, and the relative balance of use of different types of medicines. RESULTS: About one quarter of the respondents reported using no prescription or non-prescription medicines in the two days prior to being surveyed; a large majority reported using two or fewer medicines only, and use of non- prescription medicines was reported more often than prescription medicines (56% vs 48%). Use of natural health products by seniors is relatively low, but we observe a trend toward increased use in younger age groups. DISCUSSION: The findings place the consumption of prescription medicines by the elderly into a broader context that reveals that much of medicine use by the elderly involves non-prescribed products. We highlight the need to better understand seniors' decision-making regarding the different types of medicines available, and the financial costs and health risks of the medicine regimes of elderly persons.elderly, medicine-use, prescription medicines, over-the-counter medicines, natural health products, NPHS

Locality and entanglement in table-top testing of the quantum nature of linearized gravity

This paper points out the importance of the assumption of locality of physical interactions, and the concomitant necessity of propagation of an entity (in this case, off-shell quanta - virtual gravitons) between two non-relativistic test masses in unveiling the quantum nature of linearized gravity through a laboratory experiment. At the outset, we will argue that observing the quantum nature of a system is not limited to evidencing $O\left(\hbar\right)$ corrections to a classical theory: it instead hinges upon verifying tasks that a classical system cannot accomplish. We explain the background concepts needed from quantum field theory and quantum information theory to fully appreciate the previously proposed table-top experiments: namely forces arising through the exchange of virtual (off-shell) quanta, as well as Local Operations and Classical Communication (LOCC) and entanglement witnesses. We clarify the key assumption inherent in our evidencing experiment, namely the locality of physical interactions, which is a generic feature of interacting systems of quantum fields around us, and naturally incorporates micro-causality in the description of our experiment. We also present the types of states the matter field must inhabit, putting the experiment on firm relativistic quantum field theoretic grounds. At the end we use a non-local theory of gravity to illustrate how our mechanism may still be used to detect the qualitatively quantum nature of a force when the scale of non-locality is finite. We find that the scale of non-locality, including the entanglement entropy production in local/ non-local gravity, may be revealed from the results of our experiment.Comment: 12 pages, 4 figures, Accepted for publication into Physical Review

Qudits for Witnessing Quantum Gravity Induced Entanglement of Masses Under Decoherence

Recently a theoretical and an experimental protocol known as quantum gravity induced entanglement of masses (QGEM) has been proposed to test the quantum nature of gravity using two mesoscopic masses each placed in a superposition of two locations. If, after eliminating all non-gravitational interactions between them, the particles become entangled, one can conclude that the gravitational potential is induced via a quantum mediator, i.e. a virtual graviton. In this paper, we examine a range of different experimental set-ups, considering different geometries and the number of spatially superposed states taken, in order to determine which would generate entanglement faster. We conclude that without decoherence, and given a maximum distance $\Delta x$ between any two spatial states of a superposition, a set of two qubits placed in spatial superposition parallel to one another will outperform all other models given realistic experimental parameters. Furthermore, when a sufficiently high decoherence rate is introduced, multi-component superpositions can outperform the two-qubit set-up. This is further verified with an experimental simulation, showing that $O(10^3)$ measurements are required to reject the no entanglement hypothesis with a parallel qubits set-up without decoherence at a 99.9$\%$ confidence level. The number of measurements increases when decoherence is introduced. When the decoherence rate reaches $0.125$~Hz, 6-dimensional qudits are required as the two-qubit system entanglement cannot be witnessed anymore. However, in this case, $O(10^6)$ measurements will be required. One can group the witness operators to measure in order to reduce the number of measurements (up to ten-fold). However, this may be challenging to implement experimentally.Comment: 15 pages, 20 figures, 2 table

Familiar and unfamiliar face recognition in crested macaques (Macaca nigra).

Many species use facial features to identify conspecifics, which is necessary to navigate a complex social environment. The fundamental mechanisms underlying face processing are starting to be well understood in a variety of primate species. However, most studies focus on a limited subset of species tested with unfamiliar faces. As well as limiting our understanding of how widely distributed across species these skills are, this also limits our understanding of how primates process faces of individuals they know, and whether social factors (e.g. dominance and social bonds) influence how readily they recognize others. In this study, socially housed crested macaques voluntarily participated in a series of computerized matching-to-sample tasks investigating their ability to discriminate (i) unfamiliar individuals and (ii) members of their own social group. The macaques performed above chance on all tasks. Familiar faces were not easier to discriminate than unfamiliar faces. However, the subjects were better at discriminating higher ranking familiar individuals, but not unfamiliar ones. This suggests that our subjects applied their knowledge of their dominance hierarchies to the pictorial representation of their group mates. Faces of high-ranking individuals garner more social attention, and therefore might be more deeply encoded than other individuals. Our results extend the study of face recognition to a novel species, and consequently provide valuable data for future comparative studies

Catapulting towards massive and large spatial quantum superposition

A large spatial quantum superposition of size O(1-10)μm for mass m∼10-17-10-14 kg is required to probe the foundations of quantum mechanics and test the classical and quantum nature of gravity via entanglement in a laboratory. In this paper, we will show that it is possible to accelerate the two spin states of a macroscopic nanocrystal sourced by the inhomogeneous nonlinear magnetic field in a Stern-Gerlach-type setup. We will assume that the electronic spin can be embedded at the center of the nanocrystal, such as the nitrogen-vacancy (NV) center of diamond. Our analysis will be generic to any dopant or any material. We will show that we can create a desired superposition size within 1-2 s by catapulting the trajectories of the two spin states with a modest magnetic field gradient and then recombine the trajectories for a coherent interference. We will show the demanding nature of the precision required in the magnetic field to recover a 99% spin coherence confidence level at the moment of interference

Constructing nano-object quantum superpositions with a Stern-Gerlach interferometer

Probing quantum mechanics and quantum aspects of general relativity, along with the sensing and constraining of classical gravity, can all be enabled by unprecedented spatial sizes of superpositions of massive objects. In this paper, we show that there is a feasible setup sourced by realizable magnetic field gradients O(10-100)T m-1 to construct a large spatial superposition of O(10-4-10-8)m for O(10-17-10-14)kg masses within a time of up to 0.1-10 seconds. The scale of superpositions is unrestricted as long as quantum coherence can be maintained for a required amount of time

Entanglement based tomography to probe new macroscopic forces

Quantum entanglement provides a novel way to test short distance physics in the non-relativistic regime. We will provide a protocol to {\it potentially} test new physics by bringing two charged massive particle interferometers adjacent to each other. Being charged, the two superpositions will be entangled via electromagnetic interactions mediated by the photons, including the Coulomb and the Casimir-Polder potential. We will bring a method of {\it entanglement based tomography} to seek time evolution of very small entanglement phases to probe new physical effects mediated by {\it hitherto unknown macroscopic force} which might be responsible for entangling the two charged superpositions modelled by the Yukawa type potential. We will be able to constrain the Yukawa couplings $\alpha \geq 10^{-35}$ for $r\geq 10^{-6}$m for new physics occurring in the electromagnetic sector, and in the gravitational potential $\alpha_g \geq 10^{-8}$ for $r \geq 10^{-6}$m. Furthermore, our protocol can also constrain the axion like particle mass and coupling, which is complimentary to the existing experimental bounds.Comment: 7 pages, 5 fig

‘I would rather be having my leg cut off than a little needle’: A supplementary qualitative analysis of dentally anxious children’s experiences of needle fear

Fear of needles is common in childhood, with up to 50% being affected to some degree. In individuals who are dentally anxious, the prevalence may be as high as 91%. Fear of needles, and therefore intra-oral injections can have negative impacts on children’s quality of life and healthcare experiences, including a requirement for pharmacological methods to facilitate dental treatment. The aim of this study is to identify whether dentally anxious children report fear of injections and explore how these children experience a fear of needles in a dental setting. A supplementary analysis of interviews collected as part of two previous studies relating to children with dental anxiety. Five main themes were identified: feelings about needles; the nature of needle fear; the context of the fear, its consequences and how children tried to control the process. Children showed a desire to have control of their healthcare interventions, and wanted to trust the healthcare professionals giving the injections. There is evidence that children with dental anxiety also experience fear of needles, including intra-oral injections. Further primary qualitative research is needed to explore this topic in more depth and to design appropriate child centred interventions to reduce needle fear

Dimensions of young children's toothbrushing resistance: a qualitative content analysis of discussions on the online parenting forum Mumsnet

Background Young children's resistant behaviour is a barrier to parental-supervised brushing. Discussions on online parenting forums offer an insight into parental experiences, behaviour and attitudes. Analysing these discussions also demonstrates how dental advice is represented and potentially resisted. Aim To analyse how young children's toothbrushing resistance is discussed on an online parenting forum. Design Qualitative content analysis of threads on toothbrushing resistance retrieved from the UK parenting forum Mumsnet. Results A search was carried out on Mumsnet in April 2022. Overall, 204 relevant threads were identified and analysed. A coding frame was developed. Posters interacted by discussing their experiences of resistance, asking for advice, making suggestions and being both supportive and critical. Thirty-seven strategies for addressing resistance were identified. Discussions reflected attitudes and concerns relating to young children and toothbrushing resistance, including the idea brushing should be ‘non-negotiable’. A key issue was the acceptability of physical force or restraint to achieve adequate brushing. Posters invoked dental authority to support their views. Conclusion Understanding how toothbrushing resistance is discussed on a parenting forum helps establish what information and advice is shared, and highlights attitudes and concerns that shape how this problem is approached