分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Laser-induced periodic surface structures (LIPSSs) on various materials have been extensively investigated because of their wide applications. The combination of different materials allows for greater freedom in tailoring their functions and achieving responses not possible in a homogeneous material. By utilizing a femtosecond (fs) laser to irradiate the Fe-doped Polyvinyl Pyrrolidone (PVP) composite film, highly regular ultrafine nanogratings (U-nanogratings) with a period as small as 35.0 ($\pm$ 2.0) nm can be self-organized on the surface with extremely high efficiency. The period of the U-nanogratings can be controlled by varying the scanning speed of the laser beam (deposited energy) and the thickness of the composite film. Based on the experimental, theoretical, and simulation results, we propose a two-step formation mechanism: composite film excitation and two sequent grating-splitting. The high photosensitivity and low glass transition temperature of the composite film facilitate the fabrication of the ultrafine nanostructures. The proposed design method for the composite material and fabrication process could not only provide a strategy for obtaining highly regular U-nanogratings, but also offer a platform to explore the interaction physics between ultra-short pulses and matter under extreme conditions.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Optically addressable spins in two-dimensional hexagonal boron nitride (hBN) attract widespread attention for their potential advantage in on-chip quantum devices, such as quantum sensors and quantum network. A variety of spin defects have been found in hBN, but no convenient and deterministic generation methods have been reported for other defects except negatively charged boron vacancy ($\rm V_B^-$). Here we report that by using femtosecond laser direct writing technology, we can deterministically create spin defect ensembles with spectra range from 550 nm to 800 nm. Positive single-peak optically detected magnetic resonance (ODMR) signals are detected in the presence of longitudinal magnetic field, and the contrast can reach 0.8%. With the appropriate thickness of hBN flakes and femtosecond laser pulse energy, we can deterministically generate bright spin defects in-situ. Our results provide a convenient deterministic method to create spin defects in hBN, which will motivate more endeavors for future researches and applications of spin-based technologies.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Optically addressable spin defects in solid-state materials are the promising platform for quantum information applications, such as quantum network. The two-dimensional (2D) hexagonal boron nitride (hBN) as a carrier of abundant defects is an emerging candidate. While negatively charged boron vacancy (V$_\text{B}^-$) spin defect in hBN is studied intensively, the coherent control of single spin in 2D materials has not been realized yet, which constitutes the cornerstone for applying the 2D spin defect in quantum-information tasks. Here, we report the first coherent control of the single electronic spin in 2D materials at room temperature. Considering both the optical and spin properties, this defect belongs to a new type of spin defects distinguished to all other spin defects observed before. This defect has simultaneously the narrow zero-phonon line, high Debye-Waller factor, high brightness, high polarization of PL photons, low $ g^{(2)}(0) $, moderate spin $ T_{1} $ and $ T_{2} $ comparable to V$ _\text{B}^{-} $. These excellent optical properties and relatively good spin properties of this single spin lay the foundation for the applications of the 2D-material-hosted spin defects in quantum information tasks.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Quantum contextuality is one of the most perplexing and peculiar features of quantum mechanics. Concisely, it refers to the observation that the result of a single measurement in quantum mechanics depends on the set of joint measurements actually performed. The study of contextuality has a long history at University of Science and Technology of China (USTC). Here we review the theoretical and experimental advances in this direction achieved at USTC over the last 20 years. We start by introducing the renowned simplest proof of state-independent contextuality. We then present several experimental tests of quantum versus noncontextual theories with photons. Finally, we discuss the investigation on the role of contextuality in general quantum information science and its application in quantum computation.