Defect centers in diamond has outstanding properties, including long coherence times and the presence of a nuclear spin bath, which make them highly promising for quantum applications. However, the technology for large-scale integration of defect centers is still in its early stages. There are various methods for the integration of diamond centers for quantum applications. Here we focus on the hybrid integration of diamond nanophotonic structures in three aspects: 1) adiabatic coupler design, 2) pick-and-place integration of diamond chiplets with silicon nitride (SiN) photonic platform, and 3) preparation of a diamond membrane for nanofabrication. An adiabatic coupler has been designed for an existing diamond chiplet. The optimal performance has been obtained at 12 μm taper length and 120 nm tip width with an insertion loss of 0.16dB, and coupling efficiency of 78.2%. It has also been demonstrated that much better performance could be obtained by reducing the diamond waveguide thickness from 485 nm to 200 nm, giving an insertion loss of 0.094dB and a coupling efficiency of 97.2%. The optimal taper lengths in this case have been determined as 12 μm for the SiN waveguide and 8 μm for the diamond waveguide. The effect of surface treatment on the pick-and-place transfer has been investigated as well. The time dependence of the contact angle of various surface treatments applied on the SiN surface has been characterized. It has been found that the optimal pick-and-place condition can be obtained with HMDS treatment at a contact angle range of 20∘ −30∘ measured by water, corresponding to a time between 1 and 2 hours after the treatment. One issue found in pick-and-place experiments is the roughness of the diamond nanophotonic chiplet bottom surface. Etching of diamond on insulator (DOI) substrates has been performed for two kinds of diamond samples. It is found that the minimum surface roughness achievable by Ar/Cl2 + Ar/O2 etching is limited by the initial surface quality. The average surface roughness was lowered from 5.71 nm to 1.19 nm using a higher-quality diamond.

This thesis is on characterizing the superconducting properties of NbTiN thin films under cryogenic conditions for potential applications in modular quantum computers. The characterization involves development of a measurement setup using a four-point probe method, which measures resistivityof magnetron sputtered thin films of NbTiN at room temperature and (cryogenic) temperature near ab- solute zero.
The results revealed unexpected resistivity values at 3.3 K, questioning the sample’s elemental com- position. Despite superconductivity not being reached by the setup, the research shows how impor- tant optimal elemental composition is and that the implementation of pulsed currents minimizes Joule Heating.
Despite not having characterized superconducting properties, taking steps back might be essential to take a step forward in developing a quantum computer.
This thesis was carried out at TU Delft as part of the Bachelor Final Project course.

To realize large-scale, optically accessible diamond-based spin quantum systems, heterogeneous integration is essential. This involves interconnecting and manipulating defect spin qubits in diamond photonic structures via intricate photonic components and circuits fabricated from materials like silicon nitride (SiN). This thesis develops and automates a characterisation setup for photonic components operating within the visible spectrum, suitable for characterising photonic components designed to implement and integrate in diamond spin quantum systems. The main goal being achieving a transmission efficiency of more than 0.2% for the provided silicon nitride waveguides. The setup is capable of measuring power and spectral response with high precision, achieving transmission loss measurements up to 3 dB/cm, limited by current waveguide/photonic component performance, and a positional accuracy of less than 100 nm. Using silicon nitride waveguides coupled with grating couplers, transmission loss measurements were obtained that closely matched previous results, validating the setup’s accuracy. To further validate the setup, a transmission efficiency of up to 3.2% was achieved for the silicon nitride waveguides, which is more than 10 times higher than results from a comparable setup. Automated measurements show below a minute measurement time per device, enabling efficient and repeatable testing. Furthermore, the Pick and Place diamond waveguide showed a transmission of 1.7 μW with an input power of 2.75 mW. This was a first in our research group and validates the performance of the characterisation setup as well. This automated setup thus provides a scalable solution for rapid photonic component evaluation, addressing integration challenges in diamond-based quantum architectures by improving measurement throughput and coupling efficiency.

Entanglement is an essential resource for a variety of applications, such as distributed quantum computing and quantum cryptography. However, long-distance entanglement generation is challenging because of two reasons: photon loss occurs as an exponential function of distance through an optical fiber and the no-cloning theorem prevent us from directly amplifying the photons. Therefore, quantum repeaters that enable long-distance communication to realize quantum information-based protocols are desired. One way to achieve a higher entanglement generation rate is to make many attempts of generating entangled states in parallel, a process known as time-multiplexing. There has been previous work investigating the performance of time-multiplexed entanglement generation using processing nodes, but only at the elementary link level. Furthermore, this analysis was restricted to the rate of entanglement generation, with no concern for the fidelity. In this work, we go further by investigating both the fidelity and the rate of entanglement generation of time-multiplexed protocols by analyzing the secret key rate (SKR) of quantum key distribution. Moreover, we also study setups with one and two repeaters. Specifically, we investigate the impact of different hardware parameters on the SKR. Among other results, we conclude that swap gate time is a key factor for achieving higher SKR. We also examine what effect different repeater-chain protocols have on the performance of repeater chains with limited hardware resources. We find that having the repeater send photons in alternating fashion towards both end nodes results in a higher SKR than generating entanglement sequentially. Besides, we investigate what is the most efficient distribution of communication qubit (CQ) in a protocol with multiple repeaters. We ascertain that the repeater chain setup in which the number of CQs in a node is equal to that node's number of neighbors makes best use of its resources.

A new antenna measurement setup, the Antenna Dome, is being developed, which can provide real time antenna and beamformer measurements. In order to be able to validate this setup, an existing beamforming system will be will be extensively studied and characterized. Multiple measurement setups will be used, providing multiple measured characteristics. The result is an accurate statistical model for the steering system, and a comprehensive error model for the complete beamforming system, including the provided antenna array. This model will help in validating the functionality of the Antenna Dome, and ultimately will help in its further development.

In this thesis, the realization and qualification of an anechoic dome chamber for 5G antenna’s is discussed. As with audio, where no echoes or noise from outside is wanted when listening to music, when characterizing an antenna it must be prevented to get internal reflections or electromagnetic (EM) radiation from outside. For this reason, a measurement setup was simulated, using that setup, different absorbers were tested and characterized. And a Faraday cage shielding is designed and evaluated, to remove EM interference. To make the anechoic chamber physically possible, rebuilding the minidome was also required, so that the absorber and Faraday cage could be mounted on the inner wand of the dome. Eventually, a suitable test environment for 5G antenna’s is build. In the end, the assessment of the absorbing materials was completed, and the chamber achieved all requirements. Despite the space of improvement, the idea of building an anechoic chamber is successfully verified.

Resistive RAM, or RRAM, is one of the emerging non-volatile memory (NVM) technologies, which could be used in the near future to fill the gap in the memory hierarchy between dynamic RAM (DRAM) and Flash, or even completely replace Flash. RRAM operates faster than Flash, but is still non-volatile, which enables it to be used in a dense 3D NVM array. It is also a suitable candidate for computation-in-memory, neuromorphic computing and reconfigurable computing. However, the show stopping problem of RRAM is that it suffers from unique defects, which is the reason why RRAM is still not widely commercially adopted. These defects differ from those that appear in CMOS technology, due to the arbitrary nature of the forming process. They can not be detected by conventional tests and cause defective devices to go unnoticed. Therefore, new tests need to be developed that properly include the physics of a defective device in a RRAM model. Device-aware testing (DAT) is the state-of-the-art solution to this problem. By accounting for the unique physics of an RRAM device, DAT is able to detect unique RRAM defects. However, DAT bases its results on relatively compact electrical models, which do not account for randomness present in e.g. the forming of the filament and local temperature fluctuations. Meanwhile, many low-level physical models exist already that can model this randomness and provide accurate insights into the physical specifics of RRAM. These models do, however, hardly ever analyze the effects of defects. The contribution of this work is to expand and improve one of the state-of-the-art physical models to analyse manufacturing defects on a low, near atomic-level scale. For the first time, the characteristics of a defect can be described in the physical shape of the defect, rather than only the electrical consequences of a black box device. This enables deep level analysis and characterization of defects, the results of which improves DAT to detect even more unique defects. The model is applied to four types of RRAM-related defects: oxygen vacancy density fluctuation, oxide thickness variation, electrode roughness, and contamination by impurities. The effect of the defects on the conductivity of the device are observed and explained, and their unique non-linear behavior is confirmed by simulation. Dynamic defects are not yet included, but the model does provide an extensive static characterization of unique RRAM defects, providing insights into their behavior and improving the quality of DAT. Finally, a discussion is presented which criticizes the reproducability of the referenced defect-free model, but also shows the potential of this work's model to be improved.

Silicon heterojunction solar cells employing transition metal oxides as carrier selective contact are of particular interest due to the potential of reducing parasitic absorption while featuring optimal electrical properties. Recently, a record efficiency of 23.5% was achieved by employing molybdenum oxide (MoOx) as carrier selective contact. MoOx exhibits advantageous properties with respect to the p-doped standard amorphous silicon contacts due to its lower parasitic absorption and better thermal stability. However, achieving an efficient carrier collection is challenging and not well understood yet. In this work, transport of charge is studied from drift diffusion and atomistic approach by means of numerical simulations. Two different state-of-art computational tools are employed: TCAD Sentaurus for drift diffusion simulations, and VASP for ab initio simulations. Through drift diffusion simulations, the contact formation of molybdenum oxide as carrier selective contact is consistently explored including quantum confinement and transport based in mid-gap energy states. The work function of MoOx is shown to be the core for an efficient charge collection. Thanks to experimental results, it is revealed relevant phenomenon at MoOx/intrinsic amorphous silicon (i-a-Si:H) interface which includes silicon oxide formation and charge accumulated. Therefore, a special focus at interface is here presented, in order to study the inner physics of the detrimental effects and how to avoid them. Altogether, drift diffusion simulations reveal that MoOx thickness is an essential parameter because it strongly determines the work function and hence the efficiency of the solar cell. All the knowledge acquired is used to provide guidelines on the fabrication of these type of solar cells.
Looking at MoOx/a-Si:H interface, ab initio simulations are employed to study interface properties. Accordingly, such interface is analysed using both materials in their crystalline matrix. It is demonstrated that oxygen deficiency tunes the MoOx work function, a statement which is key for the proper contact formation and consistent with drift diffusion results. Finally, the charge arrangement at interface reveals the creation of an interface dipole together with silicon dioxide interlayer which is coherent with drift diffusion simulations analysis.

Electron spins trapped in quantum dots have recently proven to be a promising technology for the implementation of qubits, already demonstrating high fidelity single- and two-qubits gates. The next step towards fault-tolerant quantum computing is to increase the number of so-called spin qubits on the processor. However, this poses several challenges, one of which being how to implement single-qubit gates in multi-qubit systems, with high fidelity. This work focused on two aspects. The first one was to identify the physical phenomena and limitations that hinder the realisation of high fidelity single-qubit gates in multi-qubit environments. The second objective was to investigate, implement and optimise methods in order to minimise the impact of these perturbing phenomena. The identified perturbing effects include unwanted driving between a pulse and the neighbouring qubits, as well as frequency shifts induced by drive-spin coupling and non-ideal pulse in experimental setups. Crosstalk was addressed using pulse shaping (i.e. amplitude or phase modulation of the driving pulse to tailor its spectral characteristics and reduce the energy transmitted at unwanted frequencies). The performance of shapes taken from both NMR and signal processing literature was investigated, for various pulse parameters, through an extensive grid search. In addition, a frequency correction algorithm was devised: off-resonant drive frequencies are selected so that the shifted qubits are resonantly driven. It currently accounts for two phenomena: the AC Stark and Bloch-Siegert shifts. The algorithm furthermore tracks the changes caused by the time-dependent characteristics of the shaped pulses. The proposed frequency correction algorithm was shown to almost entirely negate the effects of the considered shifts, leading to unitary fidelity improvements by up to 55%. In addition, pulse shaping was demonstrated to noticeably improve the fidelity of simultaneous single-qubit rotations compared to unshaped driving. Rotations with fidelities as high as 99.98% were obtained for pi/2 rotations on two-qubits systems. Moreover, shapes whose Fourier transform is narrow and sharp, associated with low Rabi frequencies, were demonstrated to generally provide the highest fidelities of the tested configurations. Lastly, the trends and guidelines highlighted by these results were shown to scale to systems with larger numbers of qubits. The correction techniques investigated in this work have proven promising for the implementation of high fidelity single-qubit gates in multi-qubit systems. In particular, the guidelines for selecting a well-performing pulse shape should also be useful for the design of optimised driving schemes, regardless of the number of qubits involved. Additionally, the proposed frequency shift correction algorithm is expected to be able to handle arbitrary shifts, and so to be easily adaptable to use in experiments.

DNA aligning is a compute-intensive and time-consuming task required for all further DNA processing. It consists in finding for each DNA string from a sample its location in a reference genome. Usual techniques for short reads (hundreds of bases) involve seed-extension, where a small matching seed is found with quick search through FM-index and then extended on both ends with a custom Smith-Waterman algorithm, giving optimal solution. However this seed-extension takes a tremendous amount of time. This is why we present in this thesis a solution to offload extension on a GPU to be done in a parallel fashion. This is possible thanks to the fact that the DNA reads do not present any kind of relation between each other. We used the Burrows-Wheeler Aligner - Maximal Exact Match (BWA-MEM), a reference program in the field, to which we integrated a GPU-accelerated library for extension, GASAL2. However, BWA-MEM has a left-right dependency on extension starting scores, with the left alignment starting with the seed score, then the right part starting with the previously calculated left score. We designed a solution by starting both extensions with the seed score, we called this method the "seed-only" paradigm. On our test machine featuring 12 hyperthreaded cores and an NVIDIA Tesla K40c, when running with 12 threads, we could observe a raw kernel speed-up of 4.8x ; but if we allow non-blocking calls to let the CPU run the seeding tasks while the GPU computes the extension, we can reach a 16x effective speed-up for the extension. This extension part takes around 27% of the total time but our acceleration introduces a small overhead due to memory preparations and copying, which makes the whole application 1.28x faster, getting close to the theoretical maximum of 1.37x. Additionally, the paradigm shift we operated creates minimal differences in the final main scores on good quality alignments, with a 1.82% difference for our 5.2 million sequences data set. This makes our acceleration with GASAL2 an solid and efficient solution for a single machine.

If a practical quantum computer is to be built, it will not only need quantum programming languages and qubits, but hardware-software interfaces as well. These interfaces, also known as computer (micro)architectures are the key to creating a ’quantum stack’, where a programmer can directly execute programs onto quantum hardware. A functional quantum computer microarchitecture, the Central Controller-Light (CCLight), has been designed, implemented on a Field Programmable Gate Array (FPGA), and verified to control superconducting qubits successfully. The next logical step, in hopes of creating a more scalable quantum computing system, is to take the CCLight and implement it as an Application-Specific Integrated Circuit (ASIC). In this thesis, the CCLight was built into an ASIC. It was shown that this approach yields the potential for higher performance and lower power for the microarchitecture core, and the groundwork for more robust and automatic testing of similar microarchitectures was laid out. Lastly, the lack of scalability in the original approach, wherein the processor transmits multi-byte codewords to the analog/RF hardware controlling the qubits, was revealed.