Introduction

Over the past decade, quantum technologies have witnessed a remarkable growth in drive to surpass the research-based experiments and move towards industrial products and devices. Public accessable quantum computers with few qubits and quantum cryptography systems used in the financial industry show that this process is already a bearing fruit. The underlying basis of these new technologies is the control over quantum states, which are crucially connected to quantum mechanical effects. The exploitation of quantum mechanical properties brought out new concepts and opportunities in information technology based on the so called no cloning theorem, which allows the physical secure exchange of secret information between two parties. Another phenomenon are quantum superposition and entanglement. Quantum interference involving quantum entanglement forms the basis for quantum parallelism and is the foundation for quantum enhanced sensors.

Owing to significant experimental progress a rich collection of such physical systems have been studied and understood for a wide field of purposes, reaching from fundamental physical questions to potential applications in industry. Examples for such devices are superconducting circuits, trapped atoms and ions, single electron transistors, quantum dots and atomic-scale defects. In many of these systems a fundamental and pure quantum mechanical property is used to process quantum information, namely the spin. From a classical viewpoint the spin can be imagined as a tiny magnetic moment. However, when an electron spin is measured under the influence of a magnetic field, there are only two possible measurement outcomes: either parallel or anti-parallel with respect to the magnetic field. Those discrete outcomes are based on the fundamental quantum mechanical nature of spins. Spin ensembles have found various applications in magnetic resonance imaging techniques and in magneto-electronic devices. However, when it comes to quantum information carriers, individual spins are necessary. Spins originating from atomic-scale defects have attracted a remarkable amount of interest, because their quantum state can be initialized, manipulated and read out even at room temperature. The quantum state is not limited to single electron spins, because its state can also be transferred to a nuclear spin, which can then serve as a long lived memory. The enabling mechanism for manipulation of single spins is the connection of photoluminescence and the electron’s spin degree of freedom. This connection offers the ability to use spin and optical properties to encode information.

One of the most prominent and promising solid state system operating at room temperature is the nitrogen vacancy center in diamond. It is one of over one hundred known defects in the diamond lattice. All of these defects are formed by impurities and/or vacancies of the diamond’s pure carbon lattice. The NV-center is formed by a vacancy and a substitutional nitrogen atom. It is one of the most prominent candidates for a solid-state single-photon source with a net non-zero electron spin. The system can also be coupled to nearby nuclear spins which enables simple and advanced quantum gates for quantum information processing, as well as enabling the sensing of quantities such as strain, magnetic and electric fields, and temperature. The NV-center is also the most smallest sensor, due to its atom sized extend. Such defects in solids enable measurements close to the region of interest. Motivated by the numerous experiments, which were conducted during the last two decades, the research was extended to other similar systems not only in diamond, but also in other host crystals. Impurities in silicon for instance offer electrical initialization and readout of the spin state, but their operation is limited to low temperatures. Though, electrical readout is also possible for the NV center in diamond, it is difficult to create necessary electronic structures. A combination of the good electrical properties of silicon and optical transparency of diamond can be found in silicon carbide (SiC). The main advantage of SiC is that adding dopants for the creation of electronic device is a matter of changing the growth conditions or can be achieved by post implantation, which can be done easily and efficiently. This ability offers new possibilities for a new generation of SiC based devices combining spin-dependent effects and standard microelectronics.