Development of quantum discrete frequency combs techniques

我们圆满完成了原计划2015财年和2016财年的主要任务。在2015财年，我们建造了一台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)。该实验不仅可以加深我们对HOMI-IPS的频域理解，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。这一研究成果于2015年发表在《光学快报》上。在2016财年，我们成功地在Hong-Ou-Mandel干涉中产生了离散频率模。这些模在频域中均匀分布，因此具有一种频率梳结构，形成一种高维纠缠态(QUDIT)。这一结果(ARXIV：1603.07887)已经提交给一些备受瞩目的期刊。所有这些实验都是在1.5微米的电信波长下进行的，该波长最适合于长距离光通信。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，例如量子密码学。此外，不同纠缠频率模的分布也可能有助于改进量子计量学、量子远程同步，以及在电信波长上更强地违反局域真实感的基础测试。

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.