Realization of single photon source for quantum telecommunication

量子信息技术(QIT)现在吸引了很多人，因为它的功能是传统技术无法实现的。单光子产生器是实现QIT不可缺少的器件，它在每个脉冲中发出一个单光子。针对目前提出的方案存在平均光子数不到0.1且太少而不能实际使用的问题，本研究项目旨在实现一种真正的单光子发生器，它能以较高的概率发出单光子。我们的方法是利用控制光子的探测信号来控制信号光子的快门。我们在方案中的目标是：实现重复频率大于10 kHz的单光子源，并在1 ns的时间窗口内实现单光子局域化。在长达2年的项目中，我们首先完成了双光子束源的特性和单光子源系统的设计。第二年，我们成功地研制出了高速高透过率光学快门和高透过率光学延迟线。我们已经基本完成了整个实验系统的搭建，然而，由于泵浦Ar离子激光器故障的突然发生，导致了实验的延迟。在项目(2002.3)结束后，我们继续这个实验，部分是由JST-PRESTO项目支持的。总之，我们成功地进行了实验，该实验清楚地显示了在一个脉冲中产生单光子的最高概率(0.4)，并且在实验中我们观察到了小于1 ns的非常小的时间波动，这些都是我们在提案中所要达到的目标。

Quantum information technology ( QIT ) is now attracting many people because of its functions that cannot be realized using conventional technologies. A single photon generator, that emits a single photon in each pulse, is indispensable device for the realization of QIT. Recent proposals had a problem that the average number of photons are less than 0.1 and too small for the real use.In this research project, we aimed to realize a real single photon generator, which emits single photons with high probability. Our method is to control the fast gating shutter for the signal photons using the detection signals of control photons. Our goal we aimed in the proposal was as follows: The realization of single photon source with more than 10kHz repetition rate, and also the single photon should be localized with in 1ns time window.In the 2-year-long project, we first performed the characterization of the twin photon beam source and also the design of the system of the single photon source. In the second year, we succeeded in the development of the 'high-speed high-transmittance optical shutter' and 'optical delay line with high-transmittance.' We had almost finished the construction of the whole experimental system, however, the sudden accident of the trouble of the pump Argon ion laser caused the delay of the experiment unfortunately. After the end of the project (2002.3), we continued this experiment partly supported by JST-PRESTO project. In conclusion, we succeeded to perform the experiment which clearly showed the highest probability (0.4) to create single photons in a pulse, and in the experiment we observed a very small timing fluctuation less than 1ns, those are the goal we aimed in the proposal.