Development of quantum discrete frequency combs techniques

我们在2015和2016财年已经顺利完成了原计划的主要任务。在FY2015，我们构建了一个光纤光谱仪来测量独立光子源之间的光谱分辨Hong-Ou-Mandel干涉（HOMI-IPS）。该实验不仅加深了我们在频域对HOMI-IPS的理解，而且为利用光谱工程光子源验证HOMI-IPS的理论预测提供了重要的工具。这一结果发表在2015年的《光学快报》上。在2016财年，我们成功地在Hong-Ou-Mandel干扰中产生了离散频率模式。这些模式在频域中均匀分布，因此具有一种频率梳状结构，形成一种高维纠缠态（qudit）。该结果（arXiv:1603.07887）已发表在知名期刊上。这些实验都是在最适合长途光通信的1.5微米电信波长下进行的。因此，我们的技术将使我们能够提高基于光纤的量子通信的性能，例如量子密码。此外，不同纠缠频率模式的分布也可用于改进量子计量学、量子远程同步以及在电信波长上进行更强的局部实在性违反的基本测试。

We have successfully completed the main task of our original plan in Fiscal Year (FY) 2015 and 2016. In FY2015, we constructed a fiber spectrometer to measure the spectrally resolved Hong-Ou-Mandel interference between independent photon sources (HOMI-IPS). This experiment not only can deepen our understanding of HOMI-IPS in frequency domain, but also provides an important tool to test the theoretical predictions of HOMI-IPS using spectrally engineered photon sources. This result was published in Optics Express in 2015. In FY2016, we successfully generated discrete frequency modes in a Hong-Ou-Mandel interference. These modes are equally distributed in the frequency domain, and thus have a kind of frequency comb structure, forming a type of high dimensional entangled state (qudit). This result (arXiv:1603.07887) has been submitted to some high-profile journal.All of these experiments were done at 1.5 micrometer telecom wavelength, which is most suitable for long-haul optical communications. Therefore, our technology would enable us to enhance performances in optical-fiber-based quantum communication, e.g. quantum cryptography. Moreover, the distribution of distinct entangled frequency modes may also be useful for improving quantum metrology, quantum remote synchronization, as well as fundamental tests of stronger violation of local realism at the telecom wavelength.