Confocal photoluminescence characterization of silicon-vacancy color centers in 4H-SiC fabricated by a femtosecond laser

Formation of Paramagnetic Defects in the Synthesis of Silicon Carbide

Silicon carbide (SiC) is a very promising platform for quantum information processing, as it can host room temperature solid state defect quantum bits. These room temperature quantum bits are realized by paramagnetic silicon vacancy and divacancy defects in SiC that are typically introduced by irradiation techniques. However, irradiation techniques often introduce unwanted defects near the target quantum bit defects that can be detrimental for the operation of quantum bits. Here, we demonstrate that by adding aluminum precursor to the silicon and carbon sources, quantum bit defects are created in the synthesis of SiC without any post treatments. We optimized the synthesis parameters to maximize the paramagnetic defect concentrations-including already established defect quantum bits-monitored by electron spin resonance spectroscopy.

Edge State, Localization Length, and Critical Exponent from Survival Probability in Topological Waveguides

Edge states in topological phase transitions have been observed in various platforms. To date, verification of the edge states and the associated topological invariant are mostly studied, and yet a quantitative measurement of topological phase transitions is still lacking. Here, we show the direct measurement of edge states and their localization lengths from survival probability. We employ photonic waveguide arrays to demonstrate the topological phase transitions based on the Su-Schrieffer-Heeger model. By measuring the survival probability at the lattice boundary, we show that in the long-time limit, the survival probability is P=(1-e^{-2/ξ_{loc}})^{2}, where ξ_{loc} is the localization length. This length derived from the survival probability is compared with the distance from the transition point, yielding a critical exponent of ν=0.94±0.04 at the phase boundary. Our experiment provides an alternative route to characterizing topological phase transitions and extracting their key physical quantities.

Numerical study of silicon vacancy color centers in silicon carbide by helium ion implantation and subsequent annealing

Molecular dynamics simulation is adopted to discover the formation mechanism of silicon vacancy color center and to study the damage evolution in 4H-SiC during helium ion implantation with different annealing temperatures. The number and distribution of silicon vacancy color centers during He ion implantation can be more accurately simulated by introducing the ionization energy loss during implantation. A new method for numerical statistic of silicon vacancy color centers is proposed, which takes into account the structure around the color centers and makes statistical results more accurate than the Wigner-Seitz defect analysis method. Meanwhile, the photoluminescence spectra of silicon vacancy color centers at different helium ion doses are characterized to verify the correctness of the numerical analysis. The new silicon vacancy color center identification method can help predicting the optimal annealing temperature for silicon vacancy color centers, and provide guidance for subsequent color center annealing experiments.

Deep diamond single-photon sources prepared by a femtosecond laser

Nitrogen-vacancy color centers (NVs) in diamond have several potential applications ranging from quantum computing to data storage. However, artificial NVs are often close to the surface, which limits their spatial density and applicability. Here we demonstrate an effective and precise method for preparing deep single NVs in diamond. The method is based on a spatial-shaped femtosecond laser to overcome laser defocus in high-refractive materials, and realizes the preparation of single NVs at 95 µm. In addition, owing to the good energy distribution of the shaped laser focus, the single NVs exhibit a statistic yield of 56%±11% with excellent qualities. This processing method will contribute to the integration of color centers with emerging optical elements and high-density data storage.