In this thesis we present our experimental work towards realizing single photon spectroscopy. Based on theoretical predictions and experimental confirmation with laser absorption spectroscopy, we...Show moreIn this thesis we present our experimental work towards realizing single photon spectroscopy. Based on theoretical predictions and experimental confirmation with laser absorption spectroscopy, we identify a reltively strong transition of water vapor. This transition is in close proximity to the emission of our single photon source: a semiconductor GaAs embedded InGaAs quantum dot (QD) with emission close to 935 nm. We then show absorption spectroscopy with this single photon source where we scan the emission wavelength of the quantum dot by means of the Stark effect. In a 75 pm wide spectral range for which the source is capable of producing relatively pure single photons, which we confirm with Hanbury Brown Twiss interferometry, we measure the transmission of 261 cm humid air with QD light. We find that the observed peak wavelength and linewidth characterizing this transition compare well with the expected parameters obtained from the HITRAN database.Show less
This project employs reinforcement learning techniques to explore novel decoding strategies for quantum error correction, particularly focusing on the toric code, to address the challenge of...Show moreThis project employs reinforcement learning techniques to explore novel decoding strategies for quantum error correction, particularly focusing on the toric code, to address the challenge of maintaining stable quantum states for fault-tolerant quantum computing. Two game frameworks are established, including a novel dynamic game framework applicable to the training and measuring of RL agents and potential application in multiagent scenarios. The RL agents use Stable Baselines 3’s Proximal Policy Optimization and show to achieve Minimum Weight Perfect Matching performance on 3 × 3 toric code lattices in both the static and dynamic game frameworks.Show less
This research covers the development and application of multiple low- noise high-bandwidth lockboxes to position the mirrors of four cascaded optical cavities using piezo actuators for frequency...Show moreThis research covers the development and application of multiple low- noise high-bandwidth lockboxes to position the mirrors of four cascaded optical cavities using piezo actuators for frequency locking with a preci- sion of 40 Hz. The design and fabrication of a custom printed circuit board that hosts two ARM-based microcontrollers for signal processing are elucidated. By measuring the impedance of the piezo actuators over a large range of frequencies, we found several electromechanical resonances ranging from a few kHz to a main resonance at 80 − 100 kHz. It was found that these resonances greatly impact the ability to lock the cavity to the laser source and thereby impose bandwidth limitation on the feedback. By avoiding excitation of such resonances by reducing the feedback bandwidth to below the first prominent resonance at 2.5 kHz, we were able to achieve a high quality lock of a single optical cavity. Using a reduced bandwidth of 250 Hz and a reduced modulation frequency of 1.9 kHz, we demonstrated the locking of four cascaded cavities and achieved an optical transmission of T ≈ 40%, limited mostly by optical alignment. Finally, we show an initial lock freeze procedure for three cascaded cavities in which 90% of the transmission during the locked state is retained for a period of 4.9 seconds, while providing no feedback on the piezos.Show less
Military technological advancements have shown that autonomous drone swarms have emerged as a powerful tool for executing complex missions with enhanced resilience and efficiency, offering...Show moreMilitary technological advancements have shown that autonomous drone swarms have emerged as a powerful tool for executing complex missions with enhanced resilience and efficiency, offering significant advantages due to their collective behavior; they can operate autonomously, cover large areas, and continue missions even if individual drones fail, making them highly robust in dynamic and hazardous environments. This study uses an approach from reinforcement learning and presents a single-agent framework designed for a central-controller setup within drone swarms, and focuses on optimizing group alignment and cohesion while exploring a designated target area. Results show that smaller swarms (N = 2) achieve better cohesion and higher alignment, while increased alignment tends to reduce exploration efficiency. Performance metrics show that smaller swarms reached 69% ± 3% of optimal exploration while maintaining group alignment and cohesion, whereas larger swarms (N = 4) achieved 47%±11%, highlighting the trade-off between maintaining group cohesion and optimizing exploration.Show less
Active polymer simulations are an important aspect in understanding the physics of molecular biology. A coarse-grained view of polymers can be obtained by bead-spring simulations where particles ...Show moreActive polymer simulations are an important aspect in understanding the physics of molecular biology. A coarse-grained view of polymers can be obtained by bead-spring simulations where particles (monomers) are connected with harmonic springs in a chain-like fashion, where the spring constant is sufficiently high such that the the mean bond-length remains constant. These polymers can be made active by applying a given active force distribution on the monomers. This thesis investigates the structural and dynamical properties of polymers with different active force distributions, like time dependence or periodic active monomers. It is found that time dependent active force distributions can lead to run & tumble modes of movement. Also, novel polymer conformations, like a double helical or snake-like shape, have been found when applying periodic activity on the polymer.Show less
In quantum information theory, the presence of Bell non-local correlations is a key indicator of non-classical behavior in multipartite quantum systems. However, non-locality is not exclusive to...Show moreIn quantum information theory, the presence of Bell non-local correlations is a key indicator of non-classical behavior in multipartite quantum systems. However, non-locality is not exclusive to quantum mechanics; more general theories with stronger non-local correlations than those achievable within the quantum formalism can be constructed. While distinguishing classical (local) correlations from non-local correlations can, in principle, be accomplished by a finite number of linear constraints called Bell inequalities, distinguishing between quantum and post-quantum correlations requires solving a hierarchy of SDP relaxations. To simplify the certification of quantum correlations, a whole line of research has focused on searching for an operational principle that can explain the limited strength of quantum correlations. Among the proposed principles, information causality (IC) stands out as the most promising, though deriving general correlation bounds from it is also very complex. We review the various attempts to formalise IC and their effectiveness in constraining bipartite non-locality, as well as the challenges encountered in studying this principle. In particular, we perform numerical experiments to showcase the insufficiency of all the currently proposed IC bounds to capture the full potential of the principle for correlations near the quantum boundary. Furthermore, we demonstrate the instability of two out of three bounds under non-locality distillation.Show less
Three-dimensional galaxy surveys date back to the 1970s and provided us with a lot of information, for example, about cosmological parameters and the large-scale structure of the universe....Show moreThree-dimensional galaxy surveys date back to the 1970s and provided us with a lot of information, for example, about cosmological parameters and the large-scale structure of the universe. Similarly, halo surveys can be used to trace the underlying baryon and dark matter distribution in the future. As this method is still being developed, it is insightful to first look at simulations. Using the FLAMINGO simulation, the dependence of halo clustering on their dark matter environment is investigated. It was shown how the average local dark matter mass, which accompanies haloes, has a characteristic distribution. With haloes in high average mass regions appearing in at the centre of baryon acoustic oscillations and haloes with relatively low dark matter appearing throughout both the centre and shell. A minimal model was created, which can reconstruct this behaviour.Show less
Classical simulation of quantum processes is crucial for e.g. the testing and characterization of NISQ hardware. Although various methods exist, many suffer from the inability to capture long-range...Show moreClassical simulation of quantum processes is crucial for e.g. the testing and characterization of NISQ hardware. Although various methods exist, many suffer from the inability to capture long-range correlations, which often arise in quantum systems. As a new avenue for classical simulation, J. Carrasquilla et al. (2019) introduced a formulation of quantum dynam- ics through factorized informationally-complete positive operator valued measurements. This formulation maps quantum states to probability dis- tributions and unitary operations to quasi-stochastic matrices. Motivated by current breakthroughs in natural language processing and the ability to capture long-range correlations there-in, a transformer ansatz is trained on circuits generating graph- and GHZ states. This work introduces several extensions on this simulation by considering the physicality of the model probability distribution to improve on the optimization. Using simulation with small time steps of the unitary generating Hamiltonian, it was shown that the model stays on the boundary of the QPlex throughout optimiza- tion, at the expense of accuracy caused by built-up errors. To circumvent such error build-up, physicality constraints for subsystems of the quantum circuit were imposed on the model during optimization through regular- ization. No convincing improvements for constrained optimization were found compared to free optimization. Several recommendations on the physicality constraints are proposed.Show less
Understanding the early formation of attitudes towards emerging technologies, such as quantum science & technology (QS&T), is essential for aligning the effect of science communication in...Show moreUnderstanding the early formation of attitudes towards emerging technologies, such as quantum science & technology (QS&T), is essential for aligning the effect of science communication in practice with its intentions. This study explores the application of natural language processing (NLP) techniques to investigate the influence of news articles on social media comments regarding QS&T. We curated a dataset of 217 articles and 14, 391 top-level comments from Reddit. Employing GPT-4, a semi-automated annotation method was developed to label comments for sentiment and engagement towards QS&T, achieving a Cohen’s kappa of 0.82 when pooling over multiple labelling repetitions and comparing with human annotations. We then used support-vector regression to determine if news article embeddings could be used to predict comment sentiment and engagement. After experimenting with various embedding strategies, including Sentence-BERT and RoBERTa models, no significant correlations were found between article content and comment sentiment or engagement towards QS&T. Further interdisciplinary work in empirical communication research and NLP is suggested to explore alternative representations for news articles and their ability to predict perceptions in news comments.Show less
Doxorubicin, an intercalating chemotherapy medication, exerts its effects by interacting with DNA and chromatin structure. Understanding the impact of doxorubicin on the mechanical properties of...Show moreDoxorubicin, an intercalating chemotherapy medication, exerts its effects by interacting with DNA and chromatin structure. Understanding the impact of doxorubicin on the mechanical properties of DNA and chromatin is essential for optimizing its therapeutic efficacy and minimizing side effects. However, the exact mechanisms through which doxorubicin induces these changes remain poorly understood. Here we show that doxorubicin significantly increases the contour length ofDNAand induces a shift in the linking number towards negative values, as it causes DNA to untwist. Gel electrophoresis results further demonstrate histone dissociation in chromatin samples treated with doxorubicin, highlighting its disruptive effect on chromatin structure. Our findings underscore the critical importance of understanding drug-DNA interactions at the molecular level. By studying how doxorubicin modifies DNA and chromatin structure, we contribute to advancing scientific understanding and pave the way for the development of improved chemotherapeutic agents tailored to more effectively target cancer cells.Show less
This research conducts whole-brain analyses of Caenorhabditis elegans using a Spinning Disk Confocal Microscope (SDCM), while the animal navigates a chemical gradient. Initially, the aim was to...Show moreThis research conducts whole-brain analyses of Caenorhabditis elegans using a Spinning Disk Confocal Microscope (SDCM), while the animal navigates a chemical gradient. Initially, the aim was to investigate repellent behaviour. However, the repellents proved not to be compatible with our microscopic setup. Therefore, we shifted our focus to studying attractant behaviour. To learn more about the neural dynamics that convert sensory input into movement decisions, we studied the correlation between stimulus concentration and neural activity during chemotaxis. Specifically, the sign of the derivative of this concentration proved to be an insightful parameter to do so. This lead to the discovery of new neuronal loci that encode the derivative of the concentration over time. We identified four neurons in the posterior region (FLP, ADE, ADA, RMG), generalizing across animals.Show less
Understanding the collective migration in tumoroids, in-vitro tumour spheroids, provides insights into breast cancer metastasis. Recent observations by Schmidt et al. have revealed their intriguing...Show moreUnderstanding the collective migration in tumoroids, in-vitro tumour spheroids, provides insights into breast cancer metastasis. Recent observations by Schmidt et al. have revealed their intriguing mechanical and morphological properties. Here, we investigate the morphology, dynamics and mechanics of tumoroids using particle-based models of active dividing soft spheres. While cell motility has been modelled extensively using Active Brownian Particles (ABPs), tumoroids lack a 2D substrate and must obey action-reaction. We propose such a reciprocal activity, Pair ABP, and implement the extracellular matrix (ECM) as a soft passive gel. Pair ABP activity allows for cell-cell and cell-ECM "crawling". Simulations with SAMoS and wrapper cellSAMoS enable automated model execution, analysis, and visualisation. First, without the ECM, we compare ABPs to Pair ABPs and find 3D tumoroid reconfiguration driven by cell division and motility. We then study the clustering and glassy dynamics of a 2D plane filled with polydisperse active Pair ABPs. Upon implementing the 3D ECM gel, we find an asymmetric balance of cell division and ECM secretion. By varying the ECM density, cell-ECM stiffness, and cell motility, we analyse the mixing of an active-passive particle collective and spheroid unjamming. Our latest simulations resemble radial pressure and shear profiles from experiments. Overall, we demonstrate the potential of active matter for refining our understanding of tumoroid multicellular migration and potentially informing cancer treatment strategies.Show less
This research aims to develop a Scanning Tunneling Microscope (STM) at milli-Kelvin temperatures inside a dry-dilution refrigerator, at the Oosterkamp Group. Getting the STM to operate properly in...Show moreThis research aims to develop a Scanning Tunneling Microscope (STM) at milli-Kelvin temperatures inside a dry-dilution refrigerator, at the Oosterkamp Group. Getting the STM to operate properly in these extreme conditions will allow us to do scanning and spectroscopy measurements with improved resolution. However, these extreme conditions also give rise to challenges. Specifically, we analyse the contributions of the pulse tube, which causes mechanical and acoustical vibrations. We determined that the dominant vibrations entered through microphonics around the I/V- converter and its cables. This gave rise to 30 pARMS noise. By mounting the I/V-converter directly to the cryostat and fixing the cables we success- fully reduced the effect of microphonics to an upper-bound of 4 pARMS, and see potential to improve on this result. Through the feedback system this upper-bound would give rise to 0.02 A ̊ RMS amplitude oscillations of the tip-sample distance. This should not prevent us from achieving step- edge resolution or atomic resolution. Furthermore, we present new scans at room-temperature with significantly improved resolution and a scan at ultra-low temperature with a visible step-edge for the first time since 2014Show less
Cancer metastasis remains a critical area of study within the field of cancer research. The tumor microenvironment (TME), comprising various cell types and the extracellular matrix (ECM), plays a...Show moreCancer metastasis remains a critical area of study within the field of cancer research. The tumor microenvironment (TME), comprising various cell types and the extracellular matrix (ECM), plays a pivotal role in controlling tumor initiation and progression. Here we show an investigation into the mechanical phenotype of Hs 578T breast cancer cells within the TME, focusing particularly on the role of cell-ECM interactions in modulating cellular traction forces. Hs 578T cells with an integrin- α2 (ITGA2) stable knockout were utilized, and the resulting pressures were compared between the control and knockout at different collagen concentrations. Attention is hence given to the ITGA2 and its role in mediating cell-ECM interactions. Through the utilization of elastic hydrogel microparticles as localized stress sensors and advanced microscopy techniques, we show that increasing the collagen concentration results in increased traction forces exerted by control breast cancer cells. Conversely, the traction forces by ITGA2 Hs 578T knockout cells remain unaffected by changes in collagen concentration. Also, a linear relationship between the traction and its standard deviation, regardless of the Hs 578T cell type and collagen concentration, is observed. The findings contribute to a deeper understanding of cancer biomechanics, offering insights into potential therapeutic targets for inhibiting metastatic spread in breast cancer.Show less
In this research, a quantum and classical version of a value-based reinforcement learning method are compared to each other. This is done by training each of them to try and learn how to play a...Show moreIn this research, a quantum and classical version of a value-based reinforcement learning method are compared to each other. This is done by training each of them to try and learn how to play a simple game called Fox in a hole. The two models are compared to each other based on performance, training stability, convergence speed, and amount of trainable parameters. After hyperparameter tuning and further experimentation of the models, no clear difference is found between their performances and training stabilities. Nonetheless, the quantum model does seem to converge slower as the dimensionality of the game grows, and it also seems to require longer computation times than the classical model to keep up with its performance. Thus, the results suggest that for the task at hand, a classical value-based RL method is preferred over a quantum version of it.Show less
Cosmological simulations are essential to research in theoretical astrophysics. One thing in particular that needs to be studied using these is the recent observation of magnetic fields in voids....Show moreCosmological simulations are essential to research in theoretical astrophysics. One thing in particular that needs to be studied using these is the recent observation of magnetic fields in voids. This project then tests the SWIFT simulation code, and specifically its implementation of MHD, to aid with this. The simulation results are compared to the analytic solutions of the Zel’dovich pancake model, for both a 1D and 3D collapse. We add magnetic fields to this model, and derive and simulate their evolution for a number of configurations: in 1D, a parallel and perpendicular field (relative to the collapse axis), with and without resistivity; in 3D a field without resistivity. It is found that the magnetic field is simulated well, as it corresponds exactly to our solutions when we expect it to, and still looks reasonable when our solutions break down. Especially for a 3D collapse, the pancake model is not exact anymore, but the simulated field still seems to follow our general solutions. One caveat to this is that it requires a specific configuration of the code due to problems with artificial resistivity, so these still need to be fixed.Show less
