Consciousness in Quantum Physics and Meaning in the Advaita Philosophy of Adi Sankaracharya

Background: Quantum physics is both a highly topical and challenging topic of physics education. Learning quantum physics is inherently difficult because it is unimaginative, counterintuitive and fundamentally different from what learners know from their everyday life and classical physics. The results of recent studies underline that students are often not aware of the relevance of quantum physics and its technologies for their own lives, which makes studying quantum physics even more difficult. This is the starting point of this article: With the Erlanger teaching concept, we present an introductory teaching concept for quantum physics at secondary schools with the aim, among others, to raise students’ awareness of the importance of modern quantum technologies today and in the future. Purpose: In order to evaluate which conceptions about the quantum world arise among students who are introduced to quantum physics with the Erlanger concept, we conducted an interview study. Sample/Setting: A random sample of N = 25 students was interviewed after the intervention (15 male, 10 female) in order to answer the questions mentioned above. The interviews had a duration of 25 – 40 minutes. Prior to the intervention, none of the students had any classroom instruction in quantum physics. Design and Methods: The students’ answers were transcribed and then evaluated on the basis of deductive and inductive categories using qualitative content analysis. The coding was done by independent coders (𝜅=0.84,95%−𝐶𝐼 [0.68;1.00]). Additionally, a cluster analysis was performed and a three-cluster solution was extracted. The three clusters could be interpreted in terms of content and thus facilitate the characterization of occurring types of students’ conceptions after the intervention. Results: After the intervention with our concept, we found elaborated conceptions about the quantum world with the majority of respondents. 11 of the 25 students (cluster 1, labelled Primarily elaborate conception) are aware of the striking differences between quantum and classical physics, as all students in this cluster characterize the quantum world via effects or aspects that do not exist in classical physics. The importance of quantum physics for future technologies was named by the students combined in the cluster 2, labelled Quantum world as the world of technology. 10 of the students interviewed (cluster 3, labelled Quantum world as a classical world on a small scale) seem to stick to their pre-conceptions dominated by classical ways of thinking. Conclusions: Our article provides implications for both classroom practice and future research. For classroom practice, the Erlanger teaching concept serves as a proposal to bridge the gap between quantum physics and the everyday life of the learners. In addition, the results of the interview study presented in this paper make a contribution to the empirical research on students’ conceptions about quantum physics. We not only find individual, independent conceptions of learners, but we also show that there are dependencies between them, allowing us to extract types of conceptions. The extraction of such types of student conceptions for various further concepts of quantum physics will be part of future research and could contribute to our understanding of learning processes in quantum physics. Keywords: quantum physics, interview study, cluster analysis, teaching concept

Self-assembled semiconductor quantum dots confine single carriers on the nanometer-scale. For the confined carriers, quantum mechanics only allows states with discrete energies. Due to the Pauli exclusion principle, two carriers of identical spin cannot occupy the same energy level. When the quantum dot hosts more carriers (electrons or electron-holes), they fill the states according to Hund's rules. The recombination of a single exciton (a bound electron-hole pair) confined to the quantum dot gives rise to the emission of a single photon. For these reasons, quantum dots are often regarded as artificial atoms or even two-level systems.
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\nHowever, the environment of a quantum dot has a strong effect on it. The properties of a quantum dot can significantly deviate from that of an atom when it couples to continuum states in the surrounding semiconductor material; charge noise can strongly broaden the absorption of the quantum dot beyond its natural linewidth. On the other hand, designing the environment of a quantum dot enables to control its properties. Tunnel-coupling the quantum dot to a Fermi-reservoir or integrating it into cavities and waveguides are important examples.
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\nThe first part of this thesis investigates a situation in which the environment of the quantum dot is especially problematic: when the quantum dot is integrated into a nanostructured device, close-by surfaces cause significant charge noise. To reduce the charge noise, a new type of ultra-thin diode structure is developed as a host for the quantum dots. The design of the diode is challenging as it must fulfill several requirements to enable spin-physics and quantum optics on single quantum dots in nanostructures. For quantum dots embedded in the final diode structure, we simultaneously achieve full electrical control of their charge state, ultra-low charge noise, and excellent spin properties.
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\nEven when the quantum dots have a large distance to surfaces, coupling to interfaces within the semiconductor heterostructure can be a problematic source of noise and decoherence. For InGaAs quantum dots, the so-called wetting layer is an interface that forms during the growth of the quantum dots and is located in their direct spatial proximity. The continuum states of the two-dimensional wetting layer are energetically close to the $p$- and $d$-shells of the quantum dots. Problematic coupling between quantum dot and wetting layer states takes place for charged excitons. The second part of this work shows that a slight modification to the growth process of the quantum dots removes wetting layer states for electrons. The wetting-layer free quantum dots can contain more electrons than conventional InGaAs quantum dots and the linewidths of highly charged excitons significantly improve. Importantly, these quantum dots retain other excellent properties of conventional InGaAs quantum dots: control of charge and spin state, and narrow linewidths in resonance fluorescence.
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\nAlso for different types of self-assembled semiconductor quantum dots, the growth has a significant influence on the optical properties of confined excitons. In the third part of this thesis, it is investigated how nucleation processes during the growth are connected to the optical properties of GaAs quantum dots in AlGaAs. Remarkably, this connection can be studied post-growth by spatially resolved optical spectroscopy. The main experimental observation is the presence of strong correlations between the optical properties of a quantum dot and its proximity to neighboring quantum dots. In particular, the emission energy and the diamagnetic shift of the quantum dot emission are strongly correlated with the area of the so-called Voronoi cell surrounding the quantum dot. The observations can be explained with the capture zone model from nucleation theory, which shows that the optical quantum dot properties reveal information about the material diffusion during the semiconductor growth.
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\nAs explained before, the surrounding semiconductor environment can have a strong effect on the properties of quantum dots. However, even for a well-isolated quantum dot, there are higher shells of the quantum dot itself which can lead to effects beyond a two-level system. In the final part of this thesis, a radiative Auger process is investigated. The radiative Auger effect is directly connected to higher shells of the quantum dot and appears in its emission spectrum. It arises when resonantly exciting the singly charged exciton (trion). When one electron recombines radiatively with the hole, the other one can be promoted into a higher shell. The radiative Auger emission is red-shifted by the energy that is transferred to the second electron. The corresponding emission lines show a strong magnetic field dispersion which is characteristic for higher shells. The radiative Auger effect is observed on both types of quantum dots investigated before. Radiative Auger offers powerful applications: the single-particle spectrum of the quantum dot can be easily deduced from the corresponding emission energies; carrier dynamics inside the quantum dot can be studied with a high temporal resolution by performing quantum optics measurements on the radiative Auger photons.

Due to its high coherence in transmission over a large distance in the ambient environment, the quantum optical system has been a prevailing platform for long-distance quantum communication, which was recently realized over a continental distance with a low earth orbit satellite and ground stations [102, 70]. However, the pure quantum optical system has so far shown weak interactions between photon and matter, which makes it inefficient in carrying out deterministic quantum gates for quantum repeater based scalable quantum network and quantum computing. On the other hand, superconducting quantum systems operating in the microwave domain with Josephson junction transmon qubits have proven to be capable of efficient deterministic quantum operations on quantum states [86, 87, 66]. Nevertheless, such architecture is prone to errors and decoherence due to cross-talk between microwave elements in a large-scale superconducting quantum circuit. Furthermore, superconducting systems, in general, also have large footprint (100s um) elements (resonators and superconducting quantum bits) [92, 60] that limit the ability to scale up a superconducting quantum system. Moreover, microwave quantum circuits require cooling to around 10 mK, making it unsuitable for communicating quantum information outside a dilution refrigerator (DF). Micro- and nano- acoustic elements have been extensively used in conventional integrated information processing systems due to their compactness and high coherence [97]. Acoustic systems in quantum engineering also have the advantage of being a platform for universal couplings between various quantum systems including spins, optical photons, and superconducting circuits. As it will be discussed in this thesis, elements critical to scalable optical quantum network and superconducting quantum circuit can be constructed relying on the cavity optomechanics and piezoelectric interactions. Optomechanical interaction is concerned with the light pressure coupling of cavity mechanical deformation to a strong optical field. This interaction has allowed the close to mechanical ground state cooling of mechanical resonators using laser and the ultra-sensitive displacement measurement that led to the detection of gravitational waves in the LIGO collaboration [125, 25]. Optomechanical crystals (OMCs) are lithographically patterned devices which contain a periodic structure that host bandgaps for both optical band electromagnetic waves and microwave band acoustic waves. A properly engineered defect in the crystal can confine and localize acoustic and electromagnetic modes of similar wavelengths into a small mode volume [17, 20, 21]. A strong optomechanical coupling, which can be achieved between such strongly confined co-localized optical and acoustic modes, can be used in engineering the quantum state of mechanical motion to realize useful quantum devices such as a high-coherence quantum memory [74] and an optomechanical high efficiency optical isolator for unidirectionally connecting distant optical cavities via an acoustic bus [37]. To strongly couple the mechanical degree of freedom with a superconducting quantum circuit, various methods can be used, ranging from electromechanic coupling (electric coupling to a mechanically compliant capacitor), magnetomechanical coupling (magnetic coupling to a vibrating SQUID loop), and piezoelectric coupling. The recent advent of quantum acoustics [23, 8, 9] was realized with the strong piezoelectric coupling between a superconducting transmon qubit and a high-coherence mechanical resonator. The engineered strong piezoacoustic coupling provides the possibility to carry out deterministic ultra-high fidelity two-qubit quantum gates on non-classical mechanical quantum states [52]. This ability together with the recent demonstration of ultra-long phonon lifetime mechanical resonators show the possibility of integrating the ultra-high quality mechanical resonator as a compact quantum memory element and even a new ultra-compact (10s um) quantum bit architecture for scalable superconducting quantum circuits. Furthermore, the strong piezoelectric coupling that can transduce quantum state in a superconducting circuit into mechanical wave also makes it possible to efficiently transduce a quantum state between a superconducting quantum circuit and a telecommunication band optical channel via a mechanical waveguide connected to an optomechanical crystal cavity.

Atom-by-atom condensation in and electronic modification of 2D quantum box arrays

Stable quantum information in topological systems

In the context of modern approaches to quantum physics via two-state systems, the question of tools for assessing students’ understanding and for identifying learning difficulties in quantum physics arises anew because these differ from traditional approaches. In addition, there are different two-state approaches with different characteristics. One of the key points for understanding quantum physics is the measurement process as it lies at the heart of the differences between quantum and classical physics. Therefore, assessing students’ conceptions about the measurement process was regarded as a first step towards a comprehensive quantum concept inventory. Hence, a questionnaire to inquire the students’ perspective and reasoning about the measurement process as a key concept in quantum physics was developed and presented. This contribution will describe first results of its evaluation and give hints to its further development.

Unifying quantum and classical physics has proved difficult as their postulates are conflicting. Using the notion of counts of the fundamental measures—length, mass, and time—a unifying description is resolved. A theoretical framework is presented in a set of postulates by which a conversion between expressions from quantum and classical physics can be made. Conversions of well-known expressions from different areas of physics (quantum physics, gravitation, optics and cosmology) exemplify the approach and mathematical procedures. The postulated integer counts of fundamental measures change our understanding of length, suggesting that our current understanding of reality is distorted.

Digital information based on the laws of quantum mechanics promisses powerful new ways of computation and communication. However, quantum information is very fragile; inevitable errors continuously build up and eventually all information is lost. Therefore, realistic large-scale quantum information processing requires the protection of quantum bits (qubits) against errors. In this thesis we present the experimental implementation of quantum error correction protocols based on spins in diamond. In such protocols, a quantum state is protected against errors by encoding in multiple qubits. Errors can be detected and corrected by measurement of correlations, so-called stabilizer-measurements, on these qubits.The experimental work presented in this thesis employs multiple spins in diamond as qubits to explore and implement error correction protocols. The nitrogen-vacancy (NV) centre in diamond is a lattice defect consisting of a nitrogen atom (N) and a vacancy (V) on two adjacent diamond lattice sites. This defect effectively results in an electronic spin that can be addressed as a qubit. The spin state can be manipulated by microwave fields and optically read out. At liquid helium temperatures (cryogenic temperature, ~4 K = -269 C), the NV electron spin provides high-fidelity single-shot readout and long coherence times.The NV centre is surrounded by naturally available (1.1% abundance) nuclear C13 spins. As the number of spins that are close enough to the NV centre to be strongly coupled is limited, we employ the weakly coupled nuclear spins in the spin bath of the NV centre. Using dynamical decoupling techniques these nuclear spins can be detected via the NV electron spin through the hyperfine interaction. The nuclear spins are long-lived and robust against optical excitation of the NV electron spin, which can make these spins a robust quantum register for quantum error correction.In Ch. 4 we demonstrate universal control over multiple of such weakly coupled nuclear C13 spins in the environment of the NV centre at ambient temperatures. We demonstrate initialization, control and read-out of individual nuclear spins. Finally, we implement a quantum error correction protocol by encoding a quantum state in the NV electron spin and two nuclear spins. Errors are detected by un-encoding the quantum state back to the electron spin and correction via a double controlled operation.For universal fault-tolerant quantum computations it is essential that the quantum information remains encoded at all times. In Ch. 5 we present multiple rounds of quantum error correction and active feedback on a continuously encoded qubit at cryogenic temperatures. A quantum state is protected by encoding in three weakly coupled spins. Errors are detected via high-fidelity non-demolition readout of the NV electron spin and actively corrected using fast classical electronics. We demonstrate that an actively error-corrected qubit is robust against phase flip errors and show that a superposition state can live longer than the best physical qubit in the encoding.The presented methods and results can be extended to a range of future experiments. In Ch. 6 we propose the implementation of five-qubit quantum error correction, the smallest code to correct for general single-qubit errors on the physical qubits in the encoding, by extending the experimental methods as developed in Chs. 4a5. Besides the exploration and development of larger error correction protocols and fault-tolerant quantum computing, the presented quantum register based in spins in diamond can be employed as a quantum node and combined with recent advances in the realization of quantum entanglement over large distances to form quantum networks. These networks can be used to study both fundamental questions as well as future applications in quantum information technology.

Computer models and programs are one of the main tools in education, therefore, the development of a plan for their development and use in the field of education is one of the main problems. The use of computer models will help to explore a new topic, a demonstration experiment and phenomena without violating safety regulations. Many experts believe that the computer currently makes it possible to make a qualitative breakthrough in the education system. Models of physical phenomena and experiments actively shape students' knowledge. In teaching a number of sections of the physics course, such as atomic and nuclear physics, quantum mechanics, and elementary particle physics, essential questions about conducting experiments are obvious. These sections relate to important areas of physics that deal with the study of phenomena and processes in the microcosm. Therefore, due to some difficulties in equipping physics classrooms, the computer acts as an assistant. In quantum physics and atomic physics, computer models are considered that help explain the phenomena under study, the course of processes, as well as methods of working with computer programs that simulate laboratory installations in this section, since physical laboratory assistants are an integral part of training. The use of computer models and programs for educational purposes gives students a unique opportunity to plunge into the world of quantum and atomic physics. This study analyzes the effectiveness of such models in the educational process, their impact on students' understanding of the basic concepts of quantum and atomic physics, and also compiles questionnaires based on these problems. The survey covers about 40 physics teachers. The work is based on the analysis of existing pedagogical experiments and research in the field of application of computer models for teaching physics. The focus is on assessing the impact of these models on the quality of knowledge and their ability to make complex concepts accessible and understandable to students. The obtained results can serve as a basis for further improvement of methods of teaching quantum and atomic physics using computer programs. The introduction of computer programs can help the student create an effective learning environment for his work at his own pace and in collaboration with the class. It can be said that the use of models of physical processes in preparing students for effective learning opens up great opportunities for creating high-quality and new forms and methods, the use of computer models of physical phenomena plays an important role. Of particular importance in the development of students' abilities to observe, think, generalize based on observed facts, and predict the course of the observed process.

Electrical Control, Read-out and Initialization of Single Electron Spins

Spin systems and long-range interactions for quantum memories and quantum computing

As children, whispering into the ear of a friend in the presence of others allows us to pass a secret without interception, and forms one of the simplest attempts at secret communications we can employ. However, sending secret messages becomes deeply nontrivial over long distances. A solution for two parties to communicate securely is to encrypt and decrypt a message with two identical strings of bits, one for each party. In this case, the security of the encrypted message is provable and does not rely on assumptions on computational power. Quantum theory provides a clear solution for the initial distribution of these identical bit strings through Quantum Key Distribution. However, once long distances are involved, the corresponding loss involved in direct transmission ruins the effectiveness of quantum key distribution by reducing the effective rate exponentially with the distance. To circumvent the losses involved in direct transmission, quantum repeater architectures have been proposed. We present our contributions towards three aspects of quantum repeater systems in this thesis. We ensure conditions for implementing quantum repeaters with atomic ensembles, explore the option of optomechanical systems for implementing quantum repeaters and verify the success of completed quantum repeater protocols. In the first part of this thesis, we show how we can ensure conditions for the successful implementation of quantum repeater systems with atomic ensembles. These quantum repeater systems are formed with 1-dimensional networks, where the nodes are made up of quantum memories connected by means of single photons. This requires memories that are highly efficient. Also, if quantum repeater systems are implemented with hybrid resources, tunable photon waveforms will be desirable. We propose a protocol to implement quantum memories with atomic ensembles using a clear recipe to optimise the efficiency. We also demonstrate that a cold ensemble of Rubidium-87 can act as an efficient tunable source of single photons, along with flexibility in the produced temporal shapes. Next, we show how we can explore alternative options for the nodes of quantum repeater systems. We focus on optomechanical oscillators, and recognise that they can also be used as quantum memories. We present a witness to certify that this memory successfully operates in the quantum regime. Finally, we focus on the verification of successfully implemented quantum repeater protocols. This verification will be essential for certifying that quantum repeater systems operate as instructed. We use only local homodyne measurements to witness the success of the network, and find that the witness is robust to loss. We thus present distinct contributions towards three important aspects of quantum repeater systems. As far as a full-fledged quantum repeater system might seem to be right now, we have faith that our work brings the field of quantum-enabled secure communications forward.

Quantum physics has developed modern views of nature for more than a century. In addition to this traditional role, quantum physics has acquired new significance in the 21st century as the field responsible for driving and supporting nanoscience research, which will have even greater importance in the future because nanoscience will be the academic foundation for new technologies. The Department of Physics, Tokyo Institute of Technology, are now conducting a "Nanoscience and Quantum Physics" project (Physics G-COE project) supported by the Global Center of Excellence Program of the Ministry of Education, Culture, Sports, Science and Technology of Japan (MEXT) in order to promote research and education in these important academic fields. The International Symposium on Nanoscience and Quantum Physics, held in Tokyo, Japan, 26–28 January 2011 (nanoPHYS'11) was organized by the Physics G-COE project of the Tokyo Institute of Technology to provide an international forum for the open exchange of topical information and for stimulating discussion on novel concepts and future prospects of nanoscience and quantum physics. There were a total of 118 papers including 34 invited papers. This nanoPHYS'11 is the fourth symposium of this kind organized by the Tokyo Institute of Technology.Topics focused on in the symposium included: Category 1: Novel nanostructure (Nanowires, Nanotubes, Spin-related structure, etc) Category 2: Novel transport and electronic properties (Graphene, Topological insulators, Coherent control, etc) Category 3: Electronic and optical properties of nanostructure Category 4: Fundamental physics and new concept in quantum physics Category 5: Quantum Physics – Quantum information Category 6: Quantum Physics – Nuclear and Hadron Physics Category 7: Quantum Physics – Astrophysics, etc All the papers submitted to this issue have been reviewed under a stringent refereeing process, according to the normal rules of this Journal. The editors are grateful to all the authors, the referees, and all the individuals involved in the symposium organization, in particular, all the committee members and secretaries who helped to make this symposium so successful. The organizing committee would like to take this opportunity to thank the invited speakers, the session chairs, and all the attendees for their contribution to the symposium.Susumu Saito, Hidekazu Tanaka, Takashi Nakamura and Masaaki Nakamura, Editors

The recent discovery of efficient quantum algorithms for factoring and database search has shown that quantum computing would allow to solve important problems which are intractable with conventional computers. In contrast to the very demanding task of building a large-scale quantum computer, there are quantum communication protocols, e.g. quantum key distribution for cryptography, which—though still difficult—require much less effort and can be implemented with current technology. Apart from the technological motivation, the study of quantum information offers (at least) two additional benefits. First, new insight into fundamental questions on quantum mechanics, e.g. concerning non-locality and entanglement, are gained from an information-theoretical approach. And second, investigating a particular physical implementation of quantum information can give rise to independent physical results. Spintronics, the use of spin as opposed to charge in (classical) electronics is a new field for which some results presented here could be relevant. In this dissertation we investigate several theoretical aspects of the physical implementation of quantum computation and communication in which the fundamental unit of quantum information, the qubit, is represented by the spin of electrons in semiconductor quantum dots. The required coupling between the spins can be obtained by allowing for tunneling of electrons between adjacent dots, leading to a Heisenberg exchange coupling J S1 · S2 between the spins, a scenario which we study for laterally coupled quantum dots in a two-dimensional electron system, and for a three-dimensional setup with vertically coupled quantum dots. Furthermore, an alternative scheme to couple the spins via the interaction with an optical cavity mode is presented. Quantum error correction represents one of the important ingredients for the physical implementation of a quantum computer by protecting it from the e�ects of a noisy environment. As a �rst test for errorcorrection in a solid-state device using spins, we propose an optimized implementation of the most primitive error correction scheme (the threebit code). In this context, we introduce parallel switching, allowing to operate a quantum computer more e�ciently than the usual serial switching. Coupling spins with the exchange interaction J S1 �S2 is not su�cient for quantum computation; the spins also have to be addressed individually using controllable local magnetic �elds or g-factors giBi �Si in order to allow for single-qubit operations. On the one hand, we discuss several schemes for overcoming the di�culty of applying local magnetic �elds (requiring large gradients), e.g. g-factor engineering, which allows for all-electric operation of the device. On the other hand, we show that at the expense of additional devices (spins) and switching operations, single-spin rotations can be dispensed with completely. Addressing the feasibility of quantum communication with entangled electrons in mesoscopic wires, i.e. interacting many-body environments, we propose an interference experiment using a scattering set-up with an entangler and a beam splitter. The current noise for electronic singlet states turns out to be enhanced (bunching), while it is reduced for triplets (antibunching). Due to interactions, the �delity of the entangled singlet and triplet states is reduced by z4F in a conductor described by Fermi liquid theory, zF being the quasiparticle weight factor. Finally, we study the related but more general problem of the noise of the cotunneling current through one or several tunnel-coupled quantum dots in the Coulomb blockade regime. The various regimes of weak and strong, elastic and inelastic cotunneling are analyzed for quantum-dot systems (QDS) with few-level, nearly-degenerate, and continuous electronic spectra. In contrast to sequential tunneling, the noise in inelastic cotunneling can be super-Poissonian. In order to investigate strong cotunneling we develop a microscopic theory of cotunneling based on the density-operator formalism and using the projection operator technique. We have derived the master equation for the QDS and the current and noise in cotunneling in terms of the stationary state of the QDS. These results are then applied to QDS with a nearly degenerate and continuous spectrum.

Spins in semiconductor quantum dots are among the most promising candidates for the realization of a scalable quantum bit (qubit), the basic building block of a quantum computer. With this motivation, spin and orbital properties of quantum dots in three different semiconductor systems are investigated in this thesis: depletion mode quantum dots in GaAs/AlGaAs heterostructures as well as in silicon-germanium core-shell nanowires (GeSi NW), and accumulation mode quantum dots formed in a fin field-effect transistor (FinFET). The chronological order of this thesis reflects two major shifts of focus of the semiconductor spin qubit research in recent years: a transition from lateral GaAs quantum dots towards scalable, silicon-based systems and a change from electrons towards holes as the host of the spin qubit because of better prospects for spin manipulation and spin coherence. In a lateral GaAs single electron quantum dot, a new in-plane magnetic-field-assisted spectroscopy is demonstrated, which allows one to deduce the three dimensional confinement potential landscape of the quantum dot orbitals, which gives insight into the alignment of the ellipsoidal quantum dot with respect to the crystal axes. With this full model of the confinement at hand, the dependence of the spin relaxation on the direction and strength of an in-plane magnetic field is investigated. To mitigate the spin relaxation anisotropy due to anisotropic in-plane confinement of the quantum dot, said confinement is symmetrized by tuning the gate voltages to obtain a circular quantum dot. Then, the experimentally observed spin relaxation anisotropy can be attributed to the interplay of Rashba and Dresselhaus spin-orbit interaction (SOI) present in GaAs. By using a theoretical model, the strength and the relative sign of the Rashba and Dresselhaus SOI was obtained for the first time in such a quantum dot. From the dependence of the spin relaxation on the magnetic field strength, hyperfine induced phonon mediated spin relaxation was demonstrated -- a process predicted more than 15 years ago. Here, the hyperfine interaction leads to a mixing of spin and orbital degrees of freedom and facilitates spin relaxation. Limited by this relaxation process, a spin relaxation time of 57 +/- 15 s was measured -- setting the current record for spin lifetime in a nanostructure. Inspired by the unprecedented knowledge of the confinement and the SOI in the quantum dots used, a new theory to quantify the various corrections to the g-factor was developed. Later, these theoretical predictions have been experimentally validated by measurements of the g-factor anisotropy using pulsed-gate spectroscopy. Due to short spin qubit coherence time in GaAs, which is limited by the nuclear spins, a better approach is to build a spin qubit in a semiconductor vacuum with little or no nuclear spins. Because holes have minimal overlap with the nuclei of the semiconductor due to the p-type symmetry of their wave function, this type of decoherence is strongly suppressed when changing the host of the spin qubit from electrons to holes. The longer coherence times in combination with the predicted emergence of a direct type of Rashba SOI (DRSOI) -- a particularly strong and electrically controllable SOI -- motivated the investigation of hole quantum dots in GeSi NW. In this system, anisotropic behavior of the leakage current through a double quantum dot in Pauli spin blockade was observed. This anisotropy is qualitatively explained by a phenomenological model, which involves an anisotropic g-factor and an effective spin-orbit field. While the dominant type of SOI could not be resolved conclusively, the obtained data is not inconsistent with the expectation of DRSOI. Because each wire has to be placed manually, this NW based system lacks scalability. Hole and electron quantum dots in an industry-compatible silicon FinFET structure, conversely, are promising candidates for scalable spin qubits and, therefore, hold the potential to be used in a spin-based quantum computer. Recently, DRSOI was predicted to also emerge in narrow silicon channels such as FinFETs. In this thesis, the formation of accumulation mode hole quantum dots in such a FinFET structure is reported -- an important first step towards the realization of a scalable, all-electrically controllable, DRSOI hole spin qubit.