Atomic‐scale impurity spins, also called color centers, in an otherwise spin‐free diamond host lattice have proven to be versatile tools for applications in solid‐state‐based quantum technologies ranging from quantum information processing (QIP) to quantum‐enhanced sensing and metrology. Due to its wide band gap, diamond can host hundreds of different color centers. However, their suitability for QIP or sensing applications has only been tested for a handful of these, with the nitrogen vacancy (NV) strongly dominating this field of research. Due to its limited optical properties, the success of the NV for QIP applications however strongly depends on the development of efficient photonic interfaces. In the past years the negatively charged silicon vacancy (SiV−) center received significant attention due to its highly favourable spectral properties such as narrow zero phonon line transitions and weak phonon sidebands. Here, the recent work investigating the SiV center's orbital and electron spin coherence properties is reviewed as well as techniques to coherently control its quantum state using microwave as well as optical fields. Also, potential future experimental directions to improve the SiV's coherence time scale and to develop it into a valuable tool for QIP applications are outlined.
Atomic‐scale impurity spins, also called color centers, in an otherwise spin‐free diamond host lattice have proven to be versatile tools for applications in solid‐state‐based quantum technologies ranging from quantum information processing (QIP) to quantum‐enhanced sensing and metrology. Due to its wide band gap, diamond can host hundreds of different color centers. However, their suitability for QIP or sensing applications has only been tested for a handful of these, with the nitrogen vacancy (NV) strongly dominating this field of research. Due to its limited optical properties, the success of the NV for QIP applications however strongly depends on the development of efficient photonic interfaces. In the past years the negatively charged silicon vacancy (SiV−) center received significant attention due to its highly favourable spectral properties such as narrow zero phonon line transitions and weak phonon sidebands. Here, the recent work investigating the SiV center's orbital and electron spin coherence properties is reviewed as well as techniques to coherently control its quantum state using microwave as well as optical fields. Also, potential future experimental directions to improve the SiV's coherence time scale and to develop it into a valuable tool for QIP applications are outlined.
In the last decade atom-sized point defects in diamond, so called colour centres, have proven to be suitable systems for quantum information processing as well as quantum communication and sensing applications. Besides the wellknown nitrogen vacancy centre, the negatively charged silicon vacancy centre has recently proven to be a promising candidate due to its superior spectral properties such as narrow zero-phonon line widths and small phonon sidebands. In this feature article (article No.201700586) the authors summarize the center's electronic and optical properties as well as recent advances in controlling its quantum state using microwave as well as ultrafast all-optical control techniques which make it accessible for future quantum information processing applications. Moreover, the authors outline potential future experimental directions to improve the center's coherence time scale which so far is limited by phonon-induced decoherence. The cover picture shows an artistic representation of the silicon vacancy centre with its inversion-symmetric structure in a diamond crystal being addressed by an ultrashort laser pulse.
The silicon vacancy (SiV) color centers in diamond have significant potential in the fields of quantum information, nanophotonics, bioimaging and sensing, due to its good structural stability at room temperature, strong photostability, short luminescence lifetime, narrow zero-phonon line bandwidth, and avoidance of biological autofluorescence. They have attracted extensive attention and in-depth research from researchers. The applications of SiV color centers in the above areas require addressing key issues such as control over the number and charge state of SiV color centers in diamond, as well as improving the luminous efficiency. Therefore, this review summarizes some recent relevant research progress, including common methods for preparing SiV color centers, control over their luminescence intensity, preparation of SiV single-photon sources, and research on the control of SiV color center charge states. Based on these, an outlook is provided for the preparation and application of SiV color centers in diamond.
Abstract One ultimate goal of quantum information processing is to construct a quantum network for direct sharing of quantum information between distant parties based on stationary qubits for information storage and flying qubits for information transmission. This requires long‐lived quantum memories, efficient light–matter interface, and deterministic quantum gate operations. Among matter qubits, the electron spin of nitrogen vacancy center in diamond is an appealing option for its long coherence time at room temperature, deterministic microwave control, and optical preparation and readout of the qubit. However, its poor optical properties, including weak zero‐phonon‐line emission and large spectral diffusion, limit its potential for large‐scale deployment in quantum nodes. This has motivated the investigation for alternative quantum emitters that combine long‐time memory and coherent optical properties together. The emerging group‐IV split‐vacancy color centers in diamond, such as silicon‐vacancy, germanium‐vacancy, tin‐vacancy, and lead‐vacancy centers, are promising candidates of this ongoing exploration. These quantum emitters simultaneously possess microsecond spin coherence time and optically bright transitions with narrow linewidths. This review reports recent efforts on extending the spin coherence time of these color centers via temperature, strain, and charge control, which paves the road towards constructing solid‐based matter–photon interface for quantum network applications.
Color centers in diamond are a promising platform for quantum communication, as they can serve as solid state quantum memories with efficient optical transitions. Much recent attention has focused on the negatively charged NV center in diamond, which has a spin triplet ground state electronic configuration that can be measured and initialized optically, exhibits long spin coherence times at room temperature, and has narrow, spin-conserving optical transitions. However, the NV center exhibits a large static and dynamic inhomogeneous linewidth, and over 97% of its emission is in a broad, incoherent phonon side band, severely limiting scalability. Alternatively, the negatively charged SiV center exhibits excellent optical properties, with 70% of its emission in the zero phonon line and a narrow inhomogeneous linewidth. However, SiV− suffers from short electron spin coherence times, limited by an orbital relaxation rate (T1) of around 40 ns at 5 K.
Nitrogen-vacancy (NV) color centers in diamond have emerged as a focal point in quantum technology research due to their exceptional optical and electronic spin properties. This discovery not only expands our understanding of the material properties of diamond but also paves the way for practical applications in quantum technology. As a solid-state spin quantum system characterized by long electron spin coherence times and stable performance, NV color centers offer distinct advantages in quantum information processing. Recent advancements have enabled the fabrication of high-quality NV color centers with controllable concentration and spatial positioning through techniques such as in situ doping, ion implantation, and hybrid approaches. These technological breakthroughs have significantly enhanced the efficiency of NV center fabrication, thereby establishing a robust foundation for their widespread application in quantum sensing and quantum information technologies. This review provides a comprehensive introduction to the structure and fundamental properties of NV color centers in diamond, an in-depth analysis of recent progress in their fabrication techniques, and a critical discussion of their current applications in quantum science and technology. Additionally, the challenges, open questions, and future research directions in NV color center studies are addressed.
Abstract Complete control of the state of a quantum bit (qubit) is a fundamental requirement for any quantum information processing (QIP) system. In this context, all-optical control techniques offer the advantage of a well-localized and potentially ultrafast manipulation of individual qubits in multi-qubit systems. Recently, the negatively charged silicon vacancy centre (SiV − ) in diamond has emerged as a novel promising system for QIP due to its superior spectral properties and advantageous electronic structure, offering an optically accessible Λ -type level system with large orbital splittings. Here, we report on all-optical resonant as well as Raman-based coherent control of a single SiV − using ultrafast pulses as short as 1 ps, significantly faster than the centre’s phonon-limited ground state coherence time of about 40 ns. These measurements prove the accessibility of a complete set of single-qubit operations relying solely on optical fields and pave the way for high-speed QIP applications using SiV − centres.