Surface acoustic wave (SAW) resonators can confine and enhance the displacement associated with SAW phonons. SAW resonators are useful in quantum technology, where they are used to enhance the...Show moreSurface acoustic wave (SAW) resonators can confine and enhance the displacement associated with SAW phonons. SAW resonators are useful in quantum technology, where they are used to enhance the coupling between a single phonon and a semiconductor quantum dot (QD). In this thesis, the fabrication process of SAW resonators on GaAs with acoustic mirrors based on aluminum Bragg reflectors, and an investigation into the relation between the finesse of a resonator and the thickness of the aluminum mirrors are detailed. For this purpose, three resonators identical in design apart from the thickness of their aluminum mirrors (35 nm, 50 nm, and 100 nm) are fabricated. The finesse of these resonators is derived by examining their acoustic resonance spectra and displacement maps. Both types of measurements are performed with a fiber-based scanning Michelson interferometer. It is found that losses associated with the resonator limit the finesse. The maximal finesse is found to be F ≈ 11 for the 100 nm resonator. Based on the measurement results, it is hypothesized that reducing the resonator length will lead to a decrease in propagation loss, thereby raising the upper limit of the finesse. This project has been a step towards the optical detection of thermal phonons, with its final goal to detect single phonons.Show less
Dissipation will be introduced in to the Extended Dicke Model (EDM) using the Lindblad equation. Equations of motion and their associated fixed points will be derived using a semi-classical...Show moreDissipation will be introduced in to the Extended Dicke Model (EDM) using the Lindblad equation. Equations of motion and their associated fixed points will be derived using a semi-classical approximation. Total spin of the system will be shown to be a non-conserved quantity. It will be shown that in the Bound Luminosity State the dissipative system can be described by an EOM solely dependent on the y-component of the spin.Show less
In the large N limit, quantum field theories organise themselves into string theories. The AdS/CFT correspondence is an important class of gauge/string dualities. In this paper, we provide a...Show moreIn the large N limit, quantum field theories organise themselves into string theories. The AdS/CFT correspondence is an important class of gauge/string dualities. In this paper, we provide a literature review of a precise AdS_3/CFT_2 duality. We calculate the spectrum for the symmetric product orbifold of T^4 and show that is matches with that of the superstring theory on AdS_3 X S^3 X T^4 with one unit of NS-NS flux. Further support for the duality is obtained by matching the correlation functions at genus 0. Our analysis sheds light on why the two theories are so intimately related; it requires interpreting the worldsheet as the covering space over the boundary CFT. This is captured in a `delta function localization' property of the vertex operator correlation function. When integrated over in worldsheet moduli space, it localizes onto points that holomorphically covers the boundary sphere thus reproducing features of the dual CFT.Show less
Metamaterials feature specific properties that are not commonly found in nature. An example of such a property is input sequence sensitivity, or non-Abelian behavior. Here, we study the driving...Show moreMetamaterials feature specific properties that are not commonly found in nature. An example of such a property is input sequence sensitivity, or non-Abelian behavior. Here, we study the driving sequence dependent response of a non-Abelian metamaterial with four inputs. In previous research, these inputs were actuated with equal strength. However, in this thesis we take a novel approach by first pre-stressing the metamaterial by actuating one beam with a certain strength, and then sequentially actuating and deactuating another pair of beams using a different actuation strength. This allows us to "program" the non-Abelian response by using pre-stress. We explore this two-dimensional actuation space experimentally, and collect the ensuing behavior in a "phase diagram". We find that pre-stressing allows more complex sequential responses than without pre-stressing. In particular, pre-stressing can change the response to sequential actuation from non-Abelian to Abelian and vice-versa. Our work thus uncovers a viable strategy for externally tunable, or programmable, non-Abelian behavior.Show less
Superchirality is a property of light with not yet fully discovered future possibilities in industry and research. In this research, an attempt to obtain a bright superchiral lattice is made by...Show moreSuperchirality is a property of light with not yet fully discovered future possibilities in industry and research. In this research, an attempt to obtain a bright superchiral lattice is made by superposing four laser beams in a particular configuration. Additionally, this superposition should theoretically lead to homogeneous electric fields without modulation, which is potentially useful in microscopy. Recording the field with a simple CMOS camera and observing its fast Fourier transform gives rise to aliasing effects due to undersampling caused by the fact that interference occurs at a subpixel level. This phenomenon is investigated by numeric and analytic simulations. By rotation of the camera, pixel superresolution was achieved, which effectively enables the possibility to investigate the interference patterns at a subpixel level and hence measure the angle between pair of beams with good accuracy. With newly developed beam alignment methods we have achieved and confirmed a beam alignment that is sufficient for production of bright superchirality lattices.Show less
Scanning SQUID-on-tip (SOT) microscopy offers topographic, magnetic and thermal imaging at high sensitivities. This project focused on the development of a SOT from a self-sensing, self-actuating...Show moreScanning SQUID-on-tip (SOT) microscopy offers topographic, magnetic and thermal imaging at high sensitivities. This project focused on the development of a SOT from a self-sensing, self-actuating tuning fork AFM probe. Patterning the superconducting contacts to the SQUID was identified as the main challenge. The non-planar geometry of the probe discourages continuous film growth and prohibits the use of lithography to pattern the film. The superconducting element of the SOT must be electrically isolated from the adjacent tuning fork actuation circuit. Off-axis sputtering of 60nm NbTi was found to minimize short circuits and result in continuous superconducting films. The steps necessary to pattern the NbTi film were identified; Off-axis sputtering at a slight incline with respect to the deposition substrate and a better-fitting micromachined hard mask will enable the fabrication of a SOT atop a tuning fork AFM probe.Show less
The three pressing problems in modern particle physics, neutrino mass, baryon asymmetry and dark matter inspired various models among which many new par- ticles and experiments to either verify or...Show moreThe three pressing problems in modern particle physics, neutrino mass, baryon asymmetry and dark matter inspired various models among which many new par- ticles and experiments to either verify or exclude their existence. Among the most promising examples is the right handed neutrino or heavy neutral lepton (HNL) that has the potential to deal with all the beyond standard model (BSM) physics at once. We use fairly simple and robust pseudo-analytical methods to calculate the sensitivities of various proposed or already running BSM focused experiments among which extracted beamline experiments at CERN (SHiP, SHADOWS and NA62 DUMP), collider experiments at the LHC (MATHUSLA, Codex-b, FASER2 and FACET) and the DUNE ND detector at Fermilab. We found good agreement with sensitivities in the literature, provided a consistent way to compare different experiments and a fast and flexible way of calculating sensitivities that allows for quick adjustment in case of design changes or other developments in the field.Show less
Acoustic neutrino detection is a promising method to observe ultra high energy neutrinos. These neutrino with energies larger than 10$^{18}$ eV have a relatively low expected flux, thus a large...Show moreAcoustic neutrino detection is a promising method to observe ultra high energy neutrinos. These neutrino with energies larger than 10$^{18}$ eV have a relatively low expected flux, thus a large instrumented volume is required. Current estimations give an instrumented volume of around O(100) km$^3$ using hydrophones as the detection modules. Measuring ultra high energy neutrino would provide us with crucial information on extragalactic sources, the GZK cut-off, and also the C$\nu$B. In this work, an event detection algorithm based on clique, a subspace clustering algorithm, was developed. Furthermore, a first look at event reconstruction was taken. Ultra high energy neutrino events with energies of roughly 5 $\cdot$ 10$^{19}$ eV were approximated by using their characteristic pancake shape. An instrumented volume of 4 km$^3$ was simulated. The study has shown that a hydrophone density of 400 per km$^3$ would provide the desired detection efficiency of near 100\%. At these values a noise rate of 5 Hz can be suppressed using an amplitude criterion besides a causality one. A causality criterion alone suppresses a noise rate of 0.5-0.6 Hz. Furthermore, it was found that a configuration utilizing multiple detector blocks would maximize the effective volume of the detector. Moreover, the hydrophones should be designed for a sensitivity in the range of 0-15 kHz. The reconstruction algorithm tested did not provide the desired results, it is recommended to develop an algorithm specifically for acoustic neutrino detection. We found that design of the detector is a balancing act between detection efficiency, detector size, and noise suppression. Finally, this study demonstrates the possibility of using a clique based approach for event detection in ultra high energy neutrino detection. However, we recommend the development of noise suppression algorithms at the single waveform level, as suppression of a noise rate of 0.5-0.6 Hz or 5 Hz, depending on match criteria, is not enough based on previous research, in which noise rates can be as high as 26 Hz in low noise environments. Machine learning approaches show the most promise here.Show less
This presentation investigates the potential of applying reinforcement learning to quantum control settings through the theoretical framework of Markov decision processes (MDPs). Barry et al....Show moreThis presentation investigates the potential of applying reinforcement learning to quantum control settings through the theoretical framework of Markov decision processes (MDPs). Barry et al. formulated Quantum Observable MDPs (QOMDPs) as a model for quantum environments which Tamon claims to generalize with their introduced Quantum Partially Observable MDPs (QPOMDPs). We construct a formalism of behavioural equivalence of decision process models in order to evaluate expressibility of models through distinguishibility of models. We show that all quantum experiments can be described as POMDPs and specific environments can be modelled by varying types and formulations of decision processes with their respective advantages and disadvantages. By conducting experiments on a quantum cartpole environment, this research investigates the effects of varying environmental specifications on learning behavior and performance in quantum control problems generalized by QOMDPs in order to determine which setting is more appropriate for accurately modeling the dynamics of the system. The insights gained in this thesis can aid with appropriate model specification which is important for learning in quantum control settings. This research also contributes to the understanding of the practical implications of environmental specifications in quantum control problems, with findings having implications for the development of more effective and efficient learning algorithms tailored to quantum control settings.Show less
Surface acoustic waves (SAWs) propagate in piezoelectric materials and are generated by interdigital transducers (IDTs). SAW devices have applications in a variety of fields, under which...Show moreSurface acoustic waves (SAWs) propagate in piezoelectric materials and are generated by interdigital transducers (IDTs). SAW devices have applications in a variety of fields, under which telecommunication, biology and chemistry. The context of SAW devices in this research project is in quantum acoustics, in which the underlying idea is that quanta of sound waves (single phonons) can be used to transfer quantum information between different systems. As these systems often operate at GHz frequencies and are fabricated on Gallium Arsenide (GaAs) substrates, the goal of this research project is to fabricate (using electron-beam lithography) and characterize 1 GHz SAW devices on GaAs. The SAW emission by the IDTs is measured in the frequency domain, where good agreement is found with the coupling of modes model, allowing us to extract the SAW amplitude, the SAW velocity and the reflection coefficient of the IDT fingers. The IDTs are also measured in the time domain, were good agreement is found with the findings of the frequency domain measurements. Finally, a first step is made towards SAW resonators, which can enhance the SAW amplitudes significantly. This amplitude enhancement is crucial for quantum acoustics experiments, as high coupling between quantum dots and SAWs is needed. This project can therefore be thought of as the foundation for future quantum acoustics experiments.Show less
FUS (FUsed in Sarcoma) is a protein involved in gene expression. When a mutation occurs, FUS can build up in the cytoplasm and form droplets and fibers because of its prion-like domain. FUS protein...Show moreFUS (FUsed in Sarcoma) is a protein involved in gene expression. When a mutation occurs, FUS can build up in the cytoplasm and form droplets and fibers because of its prion-like domain. FUS protein droplets and fibers are thought to be involved in the development with brain diseases ALS and FTD, so uncovering of the kinetics of these fibers and droplets would aid in medicine development for these diseases. In this thesis, the fiber growth rate as a function of the FUS concentration in the dilute phase surrounding the fiber is measured, using confocal microscopy, by growing the fibers from FUS coated glass beads. This showed that the fiber growth rate in linearly dependent on the FUS concentrations. Secondly, the FUS droplets have been shown to age and harden over time. Here, a tentative attempt is made to quantify this hardening over time using micro rheology. This shows that this hardening indeed happens, but it is not quantifiable yet. These findings are particularly exciting as they suggest that fibril growth rate occurs through a mechanism that is contrary to that predicted from the current paradigm. Thus, this study set the foundation for a more complete physical picture of fibril growth and its alteration by condensates.Show less
Slow-roll, rapid-turn ( srrt) inflation models have recently gained some traction as a possible multifield inflation paradigm. Phenomenologically, rapid-turn inflation models have been shown to be...Show moreSlow-roll, rapid-turn ( srrt) inflation models have recently gained some traction as a possible multifield inflation paradigm. Phenomenologically, rapid-turn inflation models have been shown to be attractor solutions with at least linear stability of the perturbations by Bjorkmo (2019). In addition, srrt inflation has successfully been embedded in supergravity (Aragam et al., 2022) and simple string theory (Chakraborty et al., 2020) models. Thus, it is becoming increasingly valuable for theorists to test if their models are suitable for srrt inflation. Anguelova and Lazaroiu (2023) have derived a consistency condition purely in terms of the potential and metric of the scalar manifold for two-field inflation models. In this thesis, their consistency condition will be re-derived. In addition, we will present the inflatox python package with a numerical implementation of the consistency condition. We used inflatox to analyze four different two-field inflation models: Orbital inflation (Achúcarro et al., 2020), angular inflation (Christodoulidis et al., 2019), the egno supergravity model (Ellis et al., 2014) and a D5-brane fat inflation model from string theory (Chakraborty et al., 2020). For two of these models, we were able to numerically obtain srrt trajectories using PyTransport (Dias et al., 2016) and confirm that these trajectories overlap with the region in field space where the consistency condition holds.Show less
Sub-microsecond optoplasmonic detection has been utilized to measure the interactions of single ferritin, single apoferritin, and single gold nanospheres (GNSs) with an immobilized gold nanorod ...Show moreSub-microsecond optoplasmonic detection has been utilized to measure the interactions of single ferritin, single apoferritin, and single gold nanospheres (GNSs) with an immobilized gold nanorod (GNR) of dimensions 40 x 112 nm2. If a protein enters the near-field region of the GNR, a redshift in localized surface plasmon resonance (LSPR) occurs, which is quantified as amplitude changes in volts (V) in the performed time trace measurements of the scattered light by the GNR. This resulted in a relative change in scattering cross section (∆σ/σ) of 1.2% and 1.9% for the mean and maximum burst amplitude of the GNS, respectively. When applying the correlation between GNS and apoferritin found with the boundary element method (BEM) simulation, an expected mean burst amplitude of 0.27 mV (∆σ/σ = 0.24%) is anticipated, which falls within the achieved signal-to-noise ratio during the performed measurements. For ferritin ∆σ/σ was 0.73% and 1.04%, representing two measurements performed on different GNRs. These ∆σ/σ can be compared to 5.8% and 1.25% for GNS and ferritin, respectively, obtained from the BEM simulations, resulting in a good comparison between the measured and performed BEM simulations for the GNS and Ferritin.Show less
To study high temperature superconductors with transport experiments electrical contacts that have low contact resistance to these materials are essential. For this purpose we investigate a method...Show moreTo study high temperature superconductors with transport experiments electrical contacts that have low contact resistance to these materials are essential. For this purpose we investigate a method to fabricate silver con- tacts to BSCCO micro-crystals. We obtained the lowest contact resistances for silver contacts with a gold capping layer deposited by sputtering. The quality of the samples was further confirmed by RT measurements of the micro-crystals. Additionally, we found that the quality of most samples could be improved by annealing. This gave samples with sufficiently low contact resistances for transport experiments. Lastly, we investigated the possibility to fabricate nano-devices with Focused Ion Beam for transport experiments on the strange metal phase of BSCCO.Show less
With the development of next-generation gravitational waves detectors, we aim to measure and infer data on a broader range of the energy and redshift spectrum. However, in this range, deviations...Show moreWith the development of next-generation gravitational waves detectors, we aim to measure and infer data on a broader range of the energy and redshift spectrum. However, in this range, deviations from theories that predict a non-standard propagation speed for GWs are expected to become non negligible anymore. Moreover, it has been shown that the presence of inhomogeneities and structures in our universe does affect the GWs observables: with the forecasted level of precision of future detectors, such corrections can not be ignored. In this work we set in the frame of quartic scalar-tensor theories of gravity to study such relativistic effects with the presence of an extra scalar degree of freedom. Due to the complexity of the full theory, we opted for a phenomenological approach to describe the dispersion relation and amplitude evolution of the metric perturbation. Using this technique, we evaluated the relativistic corrections to frequency and direction of propagation of the GWs wave-vector. On the other hand, it was not possible to analytically calculate the relativistic corrections to the tensor amplitude even using the parametric approach, as a consequence of the elevated number of terms in the amplitude evolution equation. Nevertheless, after selecting from such equation the transverse-traceless modes, we were able to find, using the N-P formalism, which types of term can actually contribute to the evolution of the physical modes.Show less
The imaging of biological tissue is an important aspect to understand the human body and the processes taking place at small scales. Existing optical and electron microscopy techniques face trade...Show moreThe imaging of biological tissue is an important aspect to understand the human body and the processes taking place at small scales. Existing optical and electron microscopy techniques face trade-offs between resolution and beam damage. Optical near-field electron microscopy (ONEM) is a newly developed technique combining optical microscopy with electron microscopy. A sample is illuminated from the back with light in the visible spectrum, a near-field shadow is cast on a low workfunction photocathode. Photons are converted into electrons by the photoelectric effect and finally, the electrons exit the photocathode towards the detection optics. As a result, ONEM allows the imaging of (biological) samples without exposure to the damaging electron beam without being diffraction limited. We explore the preparation of samples suitable for ONEM experiments consisting of a fused silica substrate with an indium tin oxide (ITO) coating and a slice of biological tissue from a mouse tail. We create a cap over the biotissue from either single-layer graphene or amorphous carbon and finally, we grow a thin caesium photocathode in situ to lower the workfunction. Using a blue laser with a wavelength of 450 nm, we show for the first time that optical near-field electron microscopy can be used to image biological tissue. We can distinguish features in ONEM matching features in PEEM when overlapping the images. The resolution of these features is in the order of 100 nm when using a 5.7 μm field of view. Furthermore, we show that a carbon or graphene layer is required for ONEM imaging, yet this layer decreases the resolution of the PEEM image.Show less
