分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Photons play essential roles in fundamental physics and practical technologies. They have become one of the attractive informaiton carriers for quantum computation and quantum simulation. Recently, various photonic degrees of freedom supported by optical resonant cavities form photonic synthetic dimensions, which contribute to all-optical platforms for simulating novel topological materials. The photonic discrete or continuous degrees of freedom are mapped to the lattices or momenta of the simulated topological matter, and the couplings between optical modes are equivalent to the interactions among quasi-particles. Mature optical modulations enable flexible engineering of the simulated Hamiltonian. Meanwhile, the resonant detection methods provide direct approaches to obtaining the corresponding energy band structures, particle distributions and dynamical evolutions. In this Review, we give an overview of the synthetic dimensions in optical cavities, including frequency, orbital angular momentum, time-multiplexed lattice, and independent parameters. Abundant higher-dimensional topological models have been demonstrated in lower dimensional synthetic systems. We further discuss the potential development of photonic synthetic dimensions in the future.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Mu Yang
Hao-Qing Zhang
Yu-Wei Liao
Zheng-Hao Liu
Zheng-Wei Zhou
Xing-Xiang Zhou
Jin-Shi Xu
Yong-Jian Han
Chuan-Feng Li
Guang-Can Guo
摘要： Synthetic dimensions based on particles' internal degrees of freedom, such as frequency, spatial modes and arrival time, have attracted significant attention. They offer ideal large-scale lattices to simulate nontrivial topological phenomena. Exploring more synthetic dimensions is one of the paths toward higher dimensional physics. In this work, we design and experimentally control the coupling among synthetic dimensions consisting of the intrinsic photonic orbital angular momentum and spin angular momentum degrees of freedom in a degenerate optical resonant cavity, which generates a periodically driven spin-orbital coupling system. We directly characterize the system's properties, including the density of states, energy band structures and topological windings, through the transmission intensity measurements. Our work demonstrates a novel mechanism for exploring the spatial modes of twisted photons as the synthetic dimension, which paves the way to design rich topological physics in a highly compact platform.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Mu Yang
Hao-Qing Zhang
Yu-Wei Liao
Zheng-Hao Liu
Zheng-Wei Zhou
Xing-Xiang Zhou
Jin-Shi Xu
Yong-Jian Han
Chuan-Feng Li
Guang-Can Guo
摘要： Exceptional points (EPs), at which more than one eigenvalue and eigenvector coalesce, are unique spectral features of Non-Hermiticity (NH) systems. They exist widely in open systems with complex energy spectra. We experimentally demonstrate the appearance of paired EPs in a periodical driven degenerate optical cavity along the synthetic orbital angular momentum (OAM) dimension with a tunable parameter. The complex-energy band structures and the key features of EPs, i.e. their Fermi arcs, parity-time symmetry breaking transition, energy swapping, and half-integer band windings are directly observed by detecting the cavity's transmission spectrum. Our results advance the fundamental understanding of NH physics and demonstrate the flexibility of using the photonic synthetic dimensions to implement NH systems.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Zheng-Hao Liu
Yu Meng
Yu-Ze Wu
Ze-Yan Hao
Zhen-Peng Xu
Cheng-Jun Ai
Hai Wei
Kai Wen
Jing-Ling Chen
Jie Ma
Jin-Shi Xu
Chuan-Feng Li
Guang-Can Guo
摘要： Contextuality, a hallmark feature of the quantum theory, captures the incompatibility between quantum correlations and any noncontextual hidden-variable model. The Greenberger--Horne--Zeilinger (GHZ)-type paradoxes are proofs of contextuality which reveal this incompatibility with deterministic logical arguments. However, the simplest GHZ-type paradox with the fewest number of complete contexts and the largest degree of nonclassicality remains elusive. Here, we derive a GHZ-type paradox utilising only three complete contexts and show this number cannot be further reduced. We forward to demonstrating the paradox with an experiment which recovered all essential ingredients in a 37-dimensional contextuality test based on high-speed modulation, optical convolution and homodyne detection of time-multiplexed modes of coherent light that can be interpreted as a classical entity. By proposing and observing a strong form of contextuality in an extremely high-dimensional system, our results pave the way for the exploration of exotic quantum correlations with optical systems.
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.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Yuan-Ze Yang
Tian-Xiang Zhu
Zhi-Peng Li
Xiao-Dong Zeng
Nai-Jie Guo
Shang Yu
Yu Meng
Zhao-An Wang
Lin-Ke Xie
Zong-Quan Zhou
Qiang Li
Jin-Shi Xu
Wei Liu
Yi-Tao Wang
Jian-Shun Tang
Chuan-Feng Li
Guang-Can Guo
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
Nai-Jie Guo
Yuan-Ze Yang
Xiao-Dong Zeng
Shang Yu
Yu Meng
Zhi-Peng Li
Zhao-An Wang
Lin-Ke Xie
Jin-Shi Xu
Jun-Feng Wang
Qiang Li
Wei Liu
Yi-Tao Wang
Jian-Shun Tang
Chuan-Feng Li
Guang-Can Guo
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.
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