高精度光钟比对和频率测量

In the development of optical clocks, the absolute frequency measurement of the optical clock transitions and the comparison of different kinds of optical clocks are important steps or applications. It is also important preconditions for the reorganizations of optical clock as the secondary representations of the SI second. Calcium ion optical clocks with both uncertainty and stability at the E-17 level have been built in Wuhan institute of physics and mathematics, Chinese Academy of Sciences(WIPM), the absolute frequency of the calcium ion optical clock has also been measured via the GPS system. The measurement result is adopted by International des Poids et Mesures (CIPM) twice as the recommended frequency value of the calcium ion optical clock transition; the result hasn’t been chosen as the secondary representations of the SI second due to the relatively low measurement accuracy. In the meantime, National Institute of Metrology(NIM) has built a strontium optical lattice clock with an uncertainty at the E-16 level, the absolute transition frequency of the clock transition has been measured referenced to a cesium fountain, the measured result has been chosen as the secondary representations of the SI second. For the above reasons, here we give our proposal. We plan to transprot the calcium ion optical clock from WIPM to NIM. The cesium fountain will be used as a reference to measure the absolute frequency of the calcium ion optical clock transition, the comparison of the calcium ion optical clock and the strontium lattice clock will also be made. With the implementation of this project, the frequency ratio of different kinds of optical clock frequencies will be given, the absolute frequency of the calcium ion optical clock transition will also be measured with higher accuracy, which will make our country more competitive in the time and frequency standard regime, making our contribution to the upcoming redefinition the SI second.

光钟绝对频率测量和不同种光钟间的比对是光钟发展中的重要步骤和应用，也是光钟是否被认可为二级秒定义的关键参考。中科院武汉物理与数学研究所目前实现了不确定度和稳定度均进入E-17的钙离子光钟，并基于GPS系统测量了钙离子钟跃迁绝对频率，该测量值在2015年再次被国际计量委员会采纳作为钙离子钟跃迁频率推荐值；由于测量精度有待提高，未能进入二级秒定义。与此同时，中国计量院实现了不确定度为E-16的锶原子光钟，并基于铯喷泉钟测量了锶原子钟跃迁绝对频率，测量值进入二级秒定义。为此我们提出集成申请，计划把中科院武汉物理与数学研究所的钙离子光钟搬到计量院，基于铯喷泉钟进行钙离子光钟绝对频率测量，并与锶原子光钟进行比对。通过本项目的实施，实现不同光钟的钟跃迁频率比值测量，并给出更高精度的钙离子光钟绝对频率测量结果，使我国在国际上新一轮频标竞赛中有更多权重，在国际单位制秒的重新定义上做出我们的贡献。

光钟绝对频率测量和不同种光钟间的比对是光钟发展中的重要步骤和应用，也是光钟是否被认可为二级秒定义的关键参考。中科院精密测量科学与技术创新研究院已实现了不确定度和稳定度均进入E-17的钙离子光钟，并基于GPS系统测量了钙离子钟跃迁绝对频率，该测量值在2015年再次被国际计量委员会采纳作为钙离子钟跃迁频率推荐值；由于测量精度有待提高，未能进入二级秒定义。与此同时，中国计量院实现了不确定度为E-16的锶原子光钟，并基于铯喷泉钟测量了锶原子钟跃迁绝对频率，测量值进入二级秒定义。在上述研究基础上，我们将中科院武汉物理与数学研究所的钙离子光钟搬到计量院，基于铯喷泉钟及卫星链路溯源两种方案进行了钙离子光钟绝对频率测量。通过本项目的实施，首次给出了E-16更精度的钙离子光钟绝对频率测量结果，使我国在国际上新一轮频标竞赛中有更多权重，在国际单位制秒的重新定义上做出我们的贡献。