Quantum photonics is an emerging field of photonics where single photons are used for applications in quantum computation, quantum communication, and quantum sensing. One of the key enablers of these new technologies is colour centres. Colour centres are isolated defects in crystals that are able to emit single photons and have spin properties that can be exploited for quantum technologies. These properties include high brightness, low photo-bleaching, and room-temperature optically accessible spins. Wide-bandgap semiconductors such as diamond, silicon carbide and gallium nitride, and 2D materials such as h-BN and TMDs are of particular interest as host materials for colour centres. Numerous light emitters have been discovered and documented in these materials. Colour centres typically occur naturally in semiconductors and are often introduced during the growth process. This random distribution of defects is clearly not desirable for making quantum devices as it makes it difficult to process the materials and introduce structures that interact with these defects such as electrical contacts. The key technology that allows for the precise engineering of colour centres and other quantum defects in materials is ion implantation. Ion implantation utilizes energetic ion beams for the modification of electrical, optical, and magnetic properties of materials. It is a key processing step that has been widely used in the semiconductor industry for doping of semiconductors and for creating buried oxides. Ion implanters that are currently used in industry are designed for uniform wafer-level implantation of relatively large fluences of ions with high beam currents. The new quantum technologies, such as quantum computing, require a major paradigm shift in the way in which ion implantation is performed.
Quantum photonics is an emerging field of photonics where single photons are used for applications in quantum computation, quantum communication, and quantum sensing. One of the key enablers of these new technologies is colour centres. Colour centres are isolated defects in crystals that are able to emit single photons and have spin properties that can be exploited for quantum technologies. These properties include high brightness, low photo-bleaching, and room-temperature optically accessible spins. Wide-bandgap semiconductors such as diamond, silicon carbide and gallium nitride, and 2D materials such as h-BN and TMDs are of particular interest as host materials for colour centres. Numerous light emitters have been discovered and documented in these materials. Colour centres typically occur naturally in semiconductors and are often introduced during the growth process. This random distribution of defects is clearly not desirable for making quantum devices as it makes it difficult to process the materials and introduce structures that interact with these defects such as electrical contacts. The key technology that allows for the precise engineering of colour centres and other quantum defects in materials is ion implantation. Ion implantation utilizes energetic ion beams for the modification of electrical, optical, and magnetic properties of materials. It is a key processing step that has been widely used in the semiconductor industry for doping of semiconductors and for creating buried oxides. Ion implanters that are currently used in industry are designed for uniform wafer-level implantation of relatively large fluences of ions with high beam currents. The new quantum technologies, such as quantum computing, require a major paradigm shift in the way in which ion implantation is performed.
Color centers in wide bandgap semiconductors are prominent candidates for solid-state quantum technologies due to their attractive properties including optical interfacing, long coherence times, and spin–photon and spin–spin entanglement, as well as the potential for scalability. Silicon carbide color centers integrated into photonic devices span a wide range of applications in quantum information processing in a material platform with quantum-grade wafer availability and advanced processing capabilities. Recent progress in emitter generation and characterization, nanofabrication, device design, and quantum optical studies has amplified the scientific interest in this platform. We provide a conceptual and quantitative analysis of the role of silicon carbide integrated photonics in three key application areas: quantum networking, simulation, and computing.
Abstract Color centers in diamond, silicon carbide, and related materials have recently emerged as one of the most promising platforms for quantum technology applications. These optically active point defects in the crystal lattice demonstrate outstanding optical and spin properties at room and even higher temperatures, which can hardly be achieved using other quantum systems. For a long time, the host material was considered only as a mechanical carrier of color centers, and the fact that it is a semiconductor and, therefore, can contain high densities of electrons and holes, was ignored. However, recent studies have demonstrated that color centers can exchange electrons and holes with the valence or conduction bands of the host material, which enables novel functionalities, ranging from ultrabright electrically driven single‐photon sources to protected quantum memories. This review summarizes recent advances in understanding this interaction.
Very recently, the interest for quantum technologies by the scientific community and industry has strongly increased. Different types of implementations have been proposed as a practical implementation for a quantum bit. In particular, quantum photonics is a strong candidate for such applications. We are interested in using single photons and single spins in diamond as a solid state host matrix (nanodiamonds or membranes). Integration of nanosources of light is currently a major bottleneck preventing the realisation of all-photonic chips for quantum technologies and nanophotonics applications. Ideally, one needs optical circuitry, on-chip photodetection and on-chip generation of quantum states of light (single photons, entangled photons…). Our recent work on a new platform for quantum photonics using integrated optics can offer an easier and robust way to create compact quantum circuits that can be on chip and scalable. In this context, the coupling between waveguides and single photon emitters is critical. The goal of our research is to efficiently couple single photon emitters with a new platform made of optical glass waveguides. These waveguides are based on the so-called ion-exchange glass technology and is know in the photonics industry for quite some time but has never been used in the context of quantum technologies. Efficient light-matter interface is of primordial importance in this system. To achieve this goal, several paths are undertaken such as the use of dielectric and plasmonic structuration in order to increase the light interaction with the waveguide or to develop fabrication techniques to insert the emitters directly inside the guide (for nanodiamonds). We will show what is our current state of the art for placing single emitters at the right place on our optical waveguides made of ion-exchange in glass and in particular what can be done to improve our first promising results in order to get near unity coupling between the optical bus and single photon emitters. We will show first results with semiconductor nanocrystals (NCs) but also using nitrogen-vacancy and silicon-vacancy defects in nanodiamond. The very first step in of our approach consists in the design of the structured waveguide using electromagnetic FDTD. We demonstrated that it is possible to achieve more than 90% coupling. In practice, before using coloured centres in diamond, we started working with CdSe/ZnS semiconductor nanocrystals. So far, we use straight waveguides defined to be single modes at the nominal wavelength of the emission line of the nanoemitters. The positioning of nanoemitters is still a challenge to be achieved. We developed an original technique based on photopolymerisation of light where the nanocrystals are grafted into a light sensitive polymer and can be placed at adequate positions.
Solid-state atomic-sized color centers in wide-bandgap semiconductors, such as diamond, silicon carbide, and hexagonal boron nitride, are important platforms for quantum technologies, specifically for single-photon sources and quantum sensing. One of the emerging applications of these quantum emitters is subdiffraction imaging. This capability is provided by the specific photophysical properties of color centers, such as high dipole moments, photostability, and a variety of spectral ranges of the emitters with associated optical and microwave control of their quantum states. We review applications of color centers in traditional super-resolution microscopy and quantum imaging methods, and compare relative performance. The current state and perspectives of their applications in biomedical, chemistry, and material science imaging are outlined.
Quantum emitters serve as essential on-demand photonic resources, generating quantum states of light such as single photons and entangled photon pairs while serving as interfaces between light and matter. Buried in the solid state, quantum emitters enable a straightforward adoption of advanced nanofabrication techniques, facilitating precise engineering of their photonic environment for scalable quantum technologies. In this review, we introduce the fundamentals of quantum emitters and the key metrics characterising their performance. We highlight three material platforms: quantum dots, defect centres in diamond, and defect centres in silicon carbide. We summarise the recent developments of these platforms and discuss their advancements in quantum applications, including quantum communication, computation, and sensing. Finally, we provide a comparison across the three platforms, along with an outlook on future directions and potential challenges.
Abstract We present a high throughput and systematic method for the screening of colour centres in diamond with the aim of searching for and reproducibly creating new optical centres down to the single defect level, potentially of interest for a wide range of diamond-based quantum applications. The screening method presented here should, moreover, help to identify some already indexed defects among hundreds in diamond (Zaitsev 2001 Optical Properties of Diamond (Berlin: Springer)) but also some promising defects of a still unknown nature, such as the recently discovered ST1 centre (Lee et al 2013 Nat. Nanotechnol . 8 487; John et al 2017 New J. Phys . 19 053008). We use ion implantation in a systematic manner to implant several chemical elements. Ion implantation has the advantage of addressing single atoms inside the bulk with defined depth and high lateral resolution, but the disadvantage of producing intrinsic defects. The implanted samples are annealed in vacuum at different temperatures (between 600 °C and 1600 °C with 200 °C steps) and fully characterised at each step in order to follow the evolution of the defects: formation, dissociation, diffusion, re-formation and charge state, at the ensemble level and, if possible, at the single centre level. We review the unavoidable ion implantation defects (such as the GR1 and 3H centres), discuss ion channeling and thermal annealing and estimate the diffusion of the vacancies, nitrogen and hydrogen. We use different characterisation methods best suited for our study (from widefield fluorescence down to sub-diffraction optical imaging of single centres) and discuss reproducibility issues due to diamond and defect inhomogeneities. Nitrogen is also implanted for reference, taking advantage of the considerable knowledge on NV centres as a versatile sensor in order to retrieve or deduce the conditions and local environment in which the different implanted chemical elements are embedded. We show here the preliminary promising results of a long-term study and focus on the elements O, Mg, Ca, F and P from which fluorescent centres were found.