We demonstrate the photon-number resolution (PNR) capability of a 1.25 GHz gated InGaAs single-photon avalanche photodiode (APD) that is equipped with a simple, low-distortion ultra-narrowband interference circuit for the rejection of its background capacitive response. Through discriminating the avalanche current amplitude, we are able to resolve up to four detected photons in a single detection gate with a detection efficiency as high as 45%. The PNR capability is limited by the avalanche current saturation, and can be increased to five photons at a lower detection efficiency of 34%. The PNR capability, combined with high efficiency and low noise, will find applications in quantum information processing technique based on photonic qubits.

量子科技的发展多年来得到了光电技术的有力支撑，笔者团队由此进行了一系列光电量子器件的研究和开发。为在光纤量子通信中实现单光子信号的按需产生，笔者设计了几种微纳柱型光腔-量子点单光子源；发展了频分复用技术，研制了高纯度、高全同的宣布式单光子源；利用GaN缺陷的单光子特性，制备了室温量子随机数发生器。笔者优化周期极化铌酸锂的级联波导结构设计，大幅提升了通信波段量子纠缠光源性能，使保真度高于97%，噪声特性提高10倍；设计和制备Si₃N₄微环腔纠缠源器件，实现了99%的干涉可见度，展示了芯片集成量子光源的技术可行性；应用所制备的纠缠光源，实现了数十千米光纤基量子密钥分发和量子隐形传态。笔者发展了单光子探测器制造工程，研制了用于太阳光谱量子测量的低噪声高速雪崩单光子探测器和用于量子成像的128×32及以上规模的雪崩焦平面单光子探测器。笔者制备了光纤基量子存储器，实现了1 650个光子模式的有效存储；研究了光机械量子器件的原理机制，探索了纳米光机电系统用于量子精密测量的技术前景。希望以上综述为未来量子信息网络的发展提供研究参考和技术储备。

Recently, there has been increased attention toward 3D imaging using single-pixel single-photon detection (also known as temporal data) due to its potential advantages in terms of cost and power efficiency. However, to eliminate the symmetry blur in the reconstructed images, a fixed background is required. This paper proposes a fusion-data-based 3D imaging method that utilizes a single-pixel single-photon detector and millimeter-wave radar to capture temporal histograms of a scene from multiple perspectives. Subsequently, the 3D information can be reconstructed from the one-dimensional fusion temporal data by using an artificial neural network. Both the simulation and experimental results demonstrate that our fusion method effectively eliminates symmetry blur and improves the quality of the reconstructed images.

Efficient and precise photon-number-resolving detectors are essential for optical quantum information science. Despite this, very few detectors have been able to distinguish photon numbers with both high fidelity and a large dynamic range, all while maintaining high speed and high timing precision. Superconducting nanostrip-based detectors excel at counting single photons efficiently and rapidly, but face challenges in balancing dynamic range and fidelity. Here, we have pioneered the demonstration of 10 true photon-number resolution using a superconducting microstrip detector, with readout fidelity reaching an impressive 98% and 90% for 4-photon and 6-photon events, respectively. Furthermore, our proposed dual-channel timing setup drastically reduces the amount of data acquisition by 3 orders of magnitude, allowing for real-time photon-number readout. We then demonstrate the utility of our scheme by implementing a quantum random-number generator based on sampling the parity of a coherent state, which guarantees inherent unbiasedness, robustness against experimental imperfections and environmental noise, as well as invulnerability to eavesdropping. Our solution boasts high fidelity, a large dynamic range, and real-time characterization for photon-number resolution and simplicity with respect to device structure, fabrication, and readout, which may provide a promising avenue towards optical quantum information science.