Optical Clock Arrays for Quantum Metrology

现代世界的许多方面都以精确的时间和同步为基础，从金融交易和电网到卫星导航。这种精确的计时是由原子钟提供的，目前原子钟是基于铯等原子的微波跃迁。然而，原子钟研究目前正在经历一场革命，因为时钟从微波跃迁切换到光学跃迁，这使得最先进的时钟的性能在短短十年内提高了一百倍以上。最终，这些时钟的性能将受到统计学的限制-测量的准确性取决于独立试验的数量（就像通过多次投掷硬币来测量硬币是公平的概率一样）。实际上，这种时钟中可以使用的原子的最大数量是有限的。然而，三十多年前人们就知道，利用一种被称为纠缠的量子特性可以打破这个极限，在这种量子特性中，时钟中的原子是相关的而不是独立的。我们在这个提案中解决的最大挑战是首次在光学原子钟中创建正确的纠缠。为了做到这一点，我们将建立一种新型的光学原子钟，其中每个原子都可以独立控制。为了关联原子，我们将利用最先进的方法，将原子激发到被称为里德堡态的高能态。我们的突破目标是第一次证明在光学原子钟中进行纠缠增强测量的原理。

Many aspects of the modern world are underpinned by precise timing and synchronisation, from financial trading and power grids, to satellite navigation. This precise timing is provided by atomic clocks which are currently based on microwave transitions in atoms like caesium. However, atomic clock research is currently undergoing a revolution, as clocks switch from microwave transitions to optical transitions, which has enabled the performance of state-of-the-art clocks to improve by a factor of over one hundred in just ten years.Ultimately the performance of these clocks will be limited by statistics - the accuracy of measurements is determined by the number of independent trials (much like measuring the probability that a coin is fair by tossing it many times). In practice, the maximum number of atoms that can be used in such a clock is limited. However it has been known for over thirty years that this limit can be broken using a quantum property known as entanglement, where the atoms in the clock are correlated rather than independent.The big challenge that we address in this proposal is to create the right kind of entanglement in an optical atomic clock for the first time. To do this we will build a new type of optical atomic clock where each atom can be controlled independently. To correlate the atoms, we will exploit state-of-the-art methods based on exciting the atoms to high-energy states known as Rydberg states. The breakthrough that we target is the first proof-of-principle demonstration of an entanglement-enhanced measurements in an optical atomic clock.