由于光子在光纤中传输损耗随传输距离呈指数关系增长，目前地面安全量子通信的距离被限制在百公里量级。为了解决这一问题，1998年Briegel等人提出了量子中继方案，它基于量子存储和纠缠交换技术由短程纠缠逐步建立起长程纠缠。目前基于稀土离子掺杂晶体的固态量子存储器在保真度、带宽、容量等独立技术指标上已经展现了极大的优势及应用潜力，然而量子中继应用对存储器提出的要求是优异的综合指标，它需要存储时间为毫秒量级的高效率量子存储器。目前关于长寿命高效率固态量子存储的研究仍然是一片空白。本研究组2011年建立了基于稀土掺杂晶体的固态量子存储研究平台，目前多项技术指标上已达国际最高水平。本项目拟在已有平台的基础上，基于光学拉曼外差探测的核磁共振技术深入研究固体中稀土离子退相干的机制及调控，面向量子中继方案的具体需求，基于掺镨晶体利用原子频率梳、慢光自旋波等方案研制长寿命高效率的固态量子存储器。

Because photon loss scales exponentially with the channel length, secure quantum communication on the ground is limited to a distance of hundreds of kilometers. To overcome such limitation, Briegel et al. proposed the concept of quantum repeater in the year of 1998, which utilizes entanglement swapping and quantum memory to efficiently create long-distance entanglement from short-distance entanglement. The quantum memory based on rare-earth-on-doped crystal has shown excellent capability to store light with high fidelity and wide bandwidth as well as a large capacity, under various experimental conditions. However, the construction of a quantum repeater would require a highly efficient quantum memory with a storage time of the order of millisecond in a single system. No experiments have addressed the long-lived and efficient solid-state quantum memory so far. We established the experimental system for sold-state quantum memory in our lab in the year 2011. Now our quantum memory has the best performances in fidelity, dimensions and the multimode capacity. Based on the previous achievements, this application aims to investigate the mechanism and suppression techniques for the decoherence of rare-earth ions in solids. To fulfill the requirements of a quantum repeater, we will build the first long-lived and efficient solid-state quantum memory based on Pr-doped crystals.