量子比特的高效拓展是量子计算获取量子加速优势需要解决的基本问题, 分布式量子计算 (DQC) 因其高度可行性和灵活性, 成为解决量子比特拓展问题的关键技术之一。根据芯片间通信方式的不同, 分布式量子计算可以分为基于量子隐形传态和基于量子线路拆分的分布式量子计算两种类型, 前者主要面向容错量子计算, 而后者被认为可在中等规模含噪声量子 (NISQ) 时代有效提升量子计算机算力。从长远角度来看, 作为量子网络的主要应用之一, 分布式量子计算可以更好地整合接入量子网络的海量量子计算机以解决高难度问题。首先介绍了分布式量子计算的来源和类型, 在此基础上, 给出了两类分布式量子计算的基本原理和发展状况, 以及关注度较高的应用算法和编译优化方法。

Phase-coherent multi-tone lasers play a critical role in atomic, molecular, and optical physics. Among them, the Raman opeartion laser for manipulating atomic hyperfine qubits requires gigahertz bandwidth and low phase noise to retain long-term coherence. Raman operation lasers generated by directly modulated and frequency-multipled infrared lasers are compact and stable but lack feedback control to actively suppress the phase noise, which limits their performance in practical applications. In this work, we employ a fiber electro-optical modulator driven by a voltage-controlled oscillator (VCO) to modulate a monochromatic laser and employ a second-harmonic generation process to convert it to the visible domain, where the beat note of the Raman operation laser is stabilized by controlling the output frequency of VCO with a digital phase-locked loop (PLL). The low-frequency phase noise is effectively suppressed compared to the scheme without active feedback and it reaches -80dBc/Hz@5kHz with a 20 kHz loop bandwidth. Furthermore, this compact and robust scheme effectively reduces the system’s complexity and cost, which is promising for extensive application in atomic, molecular, and optical physics.

The ultracold molecule is a promising candidate for versatile quantum tasks due to its long-range interaction and rich internal rovibrational states. With the help of the cavity quantum electrodynamics (QED) effects, an optical cavity can be employed to increase the efficiency of the formation of the photoassociated molecules and offers a non-demolition detection of the internal states of molecules. Here, we demonstrate the production of the high-finesse optical fiber microcavity for the Rb2 molecule cavity QED experiment, which includes the fabrication of fiber-based cavity mirrors, testing, and the assembly of ultra-high vacuum-compatible optical fiber microcavity. The optical fiber microcavity offers high cooperativity between cavity mode and ultracold molecule and paves the way for the study of molecule cavity QED experimental research.

具有高品质因子（Q 值）的光学谐振腔能够长时间将光束缚在较小的模式体积内，极大地增强了光与物质的相互作用，成为集成光学器件中具有重大潜力的重要组成部分。聚焦于目前广泛应用于集成非线性光学领域的氮化硅材料平台，为了解决大尺寸氮化硅微环腔由拼接误差、表面粗糙等因素导致的散射损耗较大的问题，进行了一系列的工艺改进以提高大尺寸氮化硅微环腔的品质因子。结果表明：通过薄膜再沉积工艺可以有效降低氮化硅波导的散射损耗，半径为560 μm的大尺寸氮化硅微环腔的本征Q值得到了平均26% 的提升。得益于提高的微腔Q 值，在氮化硅微环腔中实现了重复频率40 GHz 的光学频率梳。

The microresonator-based soliton microcomb has shown a promising future in many applications. In this work, we report the fabrication of high quality (Q) Si3N4 microring resonators for soliton microcomb generation. By developing the fabrication process with crack isolation trenches and annealing, we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area. The highest intrinsic Q of the Si3N4 microring obtained in our experiments is about 6×106, corresponding to a propagation loss as low as 0.058 dBm/cm. With such a high Q film, we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power, with an optical parametric oscillation threshold of only 13.4 mW. Our Si3N4 integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.

We have demonstrated a mode matching method between two different fibers by a hybrid thermal expanded core technique, which can be applied to match the modes of fiber-based Fabry–Pérot cavities. Experimentally, this method has achieved an expansion of the ultraviolet fiber core by 3.5 times while keeping fundamental mode propagation. With the experiment parameters, the fundamental mode coupling efficiency between the fiber and micro-cavity can reach 95% for a plano-concave cavity with a length of 400 μm. This method can not only have potential in quantum photonics research but also can be applied in classical optical fields.

Higher emission rates and controllable emission direction are big concerns when it comes to finding a good single photon source. Recently, surface plasmons are introduced to this application, as they can manipulate and enhance the luminescence of single emitters. Here, we experimentally achieve a wide-area multiple directional enhanced light source through periodic metal grating structures. The surface-plasmon-coupled emission can have multiple precisely emission angles by just changing the period of the grating. Our result indicates that metal plasmonic grating can be used as a productive quantum device for unidirectional quantum light sources in quantum optics.

Loss is inevitable for the optical system due to the absorption of materials, scattering caused by the defects, and surface roughness. In quantum optical circuits, the loss can not only reduce the intensity of the signal, but also affect the performance of quantum operations. In this work, we divide losses into unbalanced linear losses and shared common losses, and provide a detailed analysis on how loss affects the integrated linear optical quantum gates. It is found that the orthogonality of eigenmodes and the unitary phase relation of the coupled waveguide modes are destroyed by the loss. As a result, the fidelity of single- and two-qubit operations decreases significantly as the shared loss becomes comparable to the coupling strength. Our results are important for the investigation of large-scale photonic integrated quantum information processes.