Optical atomic clocks

光学原子钟是我们测量时间和频率最精确的工具之一。不同系统中原子钟之间的频率比较用于大地测量，测量基本常数的时空变化，甚至探测暗物质的结构。在独立系统之间进行这种比较的精度总是受到标准量子极限的限制。这项研究的目的是利用量子网络的远程纠缠来增强这种频率比较，超越这个限制，建立在我们之前的原理证明的基础上。我们将使用混合种纠缠操作来相干地映射最初在远程锶离子上产生的远程纠缠到共捕获的钙离子。钙离子具有一阶对磁场波动不敏感的光学跃迁；我们希望在跃迁的寿命极限下进行频率比较，并实现有纠缠的实际增强的最初几个实例之一。

Optical atomic clocks are one of our most precise tools to measure time and frequency. Frequency comparisons between atomic clocks in separate systems are used for geodesy, measuring the space time variation of fundamental constants, and even probing the structure of dark matter. The precision of such comparisons between independent systems will always be limited by the standard quantum limit. This research aims to use the remote entanglement from a quantum network to enhance such frequency comparisons beyond this limit, building upon our previous proof-of-principle demonstration. We will use mixed-species entangling operations to coherently map the remote entanglement initially generated on remote strontium ions to co-trapped calcium ions. Calcium ions have an optical transition that is first-order insensitive to magnetic field fluctuations; we hope to perform frequency comparisons at the lifetime limit of the transition and achieve one of the first few instances of a practical enhancement with entanglement.