单光子探测对于量子信息和量子通信等需求意义重大，是“单量子态检测及相互作用”研究的基础。1.3至1.55微米光纤通信波段是量子信息等应用的首选波段，而该波段尚缺乏可靠易用的高性能单光子探测手段。针对此问题，本项目提出半导体红外上转换单光子探测方案：通过半导体红外探测器和发光二极管集成获得红外上转换器件，将光纤通信波段红外单光子转换为1微米波长以下近红外单光子，随后利用Si单光子探测器探测。此方案有望获得高探测效率、高最大计数率、低暗计数率、以及高工作温度，具备重要的实际应用前景。项目将深入研究半导体材料和结构中红外单光子吸收和单光生载流子输运、复合特性，实现材料生长和器件制备的精确调控，最终研制一种性能优异、结构紧凑的红外单光子探测方案。通过该项目，我们将深入研究红外单光子的吸收、单电子空穴对激发、单载流子输运和复合、单光子发射等关键科学问题，透彻理解单载流子层面的噪声机制。

Single photon detection is of great importance to quantum information and quantum communication, and is fundamental to “single quantum state measurement and interaction” research. 1.3 to 1.55um optical-fiber wavelength region is the number one chosen wavelength region for quantum information applications, however reliable and easy-to-use high performance single photon detection techniques are still lacking. Targeting this problem, this project proposes a semiconductor infrared upconversion single photon detection approach: through integrating semiconductor infrared detector and light-emitting diode resulting in infrared upconversion device, converting optical-fiber wavelength single photon into less-than-1um near-infrared single photon, using Si single-photon detection system finally realizing infrared single photon detection. This approach has the potential for high detection efficiency, high maximum-count rate, low dark count, and high-temperature operation, thus having important practical applications prospect. This research explores in details infrared single photon absorption and the resulting single carrier transport and recombination processes, realizes precise control of materials growth and device fabrication, and at the end achieves a high performance and compact single infrared photon detection technique. The scientific problems of the project include the processes of a single photon absorption and the resulting excitation of a single electron-hole pair or exciton, break-apart of electron-hole pair or exciton and the subsequent single carrier transport, and finally recombination of single electron (or hole) among a sea of holes (or electrons), which involves many-body effects, resulting in single photon emission. In addition, the physics of noise at the single carrier level must be studied to ensure that the upconversion process generates no or minimal noise.