With energy–time entangled biphoton sources as the optical carrier and time-correlated single-photon detection for high-speed radio frequency (RF) signal recovery, the method of quantum microwave photonics (QMWP) has presented the unprecedented potential of nonlocal RF signal encoding and efficient RF signal distilling from the dispersion interference associated with ultrashort pulse carriers. In this paper, its capability in microwave signal processing and prospective superiority are further demonstrated. Both QMWP RF phase shifting and transversal filtering functionality, which are the fundamental building blocks of microwave signal processing, are realized. Besides good immunity to the dispersion-induced frequency fading effect associated with the broadband carrier in classical MWP, a native two-dimensional parallel microwave signal processor is provided. These results well demonstrate the superiority of QMWP over classical MWP and open the door to new application fields of MWP involving encrypted processing.

We report an all-fiber telecom-band energy-time entangled biphoton source with all physical elements integrated into a compact cabinet. At a pump power of 800 µW, the photon pairs generation rate reaches 6.9 MHz with the coincidence-to-accidental ratio (CAR) better than 1150. The long-term stability of the biphoton source is characterized by measuring the Hong–Ou–Mandel interference visibility and CAR within a continuous operation period of more than 10 h. Benefiting from the advantages of compact size, light weight, and high stability, this device provides a convenient resource for various field turnkey quantum communication and metrology applications.

提出了一种噪声抑制方法，设计了基于3×3光纤耦合器迈克尔逊干涉仪的频率传递系统，使用嵌入式系统进行控制，通过调整光纤长度，实时补偿由温度变化等环境因素引起的时延变化，并进行了实验验证。启用时延补偿后，实验用的30 m长传输光纤在环境温度变化21℃条件下长度变化量小于±1 μm，对应时间延迟变化量小于10 fs，所传输的光梳重频信号的频率稳定度没有明显变化。本文工作有望为空间条件下的光钟信号向比对设备的传输路径噪声抑制提供有效的解决方法。

As the main branch of microwave photonics, radio-over-fiber technology provides high bandwidth, low-loss, and long-distance propagation capability, facilitating wide applications ranging from telecommunication to wireless networks. With ultrashort pulses as the optical carrier, a large capacity is further endowed. However, the wide bandwidth of ultrashort pulses results in the severe vulnerability of high-frequency radio frequency (RF) signals to fiber dispersion. With a time-energy entangled biphoton source as the optical carrier combined with the single-photon detection technique, a quantum microwave photonics method in radio-over-fiber systems is proposed and demonstrated experimentally. The results show that it not only realizes unprecedented nonlocal RF signal modulation with strong resistance to the dispersion but also provides an alternative mechanism to distill the RF signal out from the dispersion effectively. Furthermore, the spurious-free dynamic ranges of the nonlocally modulated and distilled RF signals have been significantly improved. With the ultra-weak detection and the high-speed processing advantages endowed by the low-timing-jitter single-photon detection, the quantum microwave photonics method opens new possibilities in modern communication and networks.

A hertz-linewidth ultra-stable laser (USL), which will be used to detect the clock transition line, in a strontium optical clock will be launched into the China Space Station (CSS) in late 2022. As the core of the USL, an interference-filter-based external-cavity diode laser (IF-ECDL) was developed. The IF-ECDL has a compact, stable, and environmentally insensitive design. Performances of the IF-ECDL are presented. The developed IF-ECDL can pass the aerospace environmental tests, indicating that the IF-ECDL can be suitable for space missions in the CSS.

为了实现高稳定度的锶原子光钟，设计了基于30 cm腔超稳激光系统。系统性评估并抑制了系统中存在的主要噪声，将参考腔的振动不敏感度降低到6×10^-10/g，对应的频率不稳定度小于3.6×10^-16；使用真空室内控温的方法，将控温层的温度变化减小到0.4 mK以内，腔上温度起伏在1 Hz处相比实验室环境温度降低了5个数量级；功率抖动经抑制达到了1 pW，对应的频率不稳定度为2.4×10^-19@1 s；剩余幅度噪声、光纤相位噪声经抑制后均小于3×10^-16，完全满足达到10^-16量级超稳激光的条件。与10 cm腔超稳激光系统进行拍频比对，综合拍频结果和噪声分析显示，系统锁定后激光频率不稳定度的秒稳小于6.2×10^-16。

We propose and demonstrate an experimental implementation for the observation of magnetic fields from spatial features of absorption profiles in a warm atomic vapor. A radially polarized vector beam that traverses atomic vapor will generate an absorption pattern with a petal-like structure by the mediation of a transverse magnetic field (TMF). The spatial absorption pattern rotates when the azimuthal angle of the TMF is changed, while its contrast decreases when the longitudinal component of the magnetic field increases. By analyzing the intensity distribution of the transmitted pattern, we can determine the magnetic field strength. Our work provides a framework for investigating 3D magnetic field distributions based on atoms.