长寿命高效率固态量子存储器的实验研究

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.

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。

周宗权带领中国科大固态量子存储研究团队实现多模式量子中继并证实量子U盘的可行性。远程量子通信是当今量子信息科学的核心难题之一，量子中继和量子U盘（即可移动的量子存储）是实现远程量子通信的两种可行方案。周宗权提出具有自主知识产权的原创量子存储方案“无噪声光子回波”，可提升量子U盘的存储效率及信噪比超过4倍；他带领团队实现一种新型量子中继架构，即基于吸收型存储的多模式量子中继，并将相干光的存储时间提升至1个小时，大幅刷新此前的世界记录（1分钟），证实了光量子U盘的原理可行性。以上成果显著推进了远程量子通信领域的发展，形成的论文包括Nature一篇（封面故事）及Nature子刊、PRL等多篇，受到了国内外媒体的广泛关注，并入选两院院士评选的2021年中国十大科技进展新闻。