Optical lattice atomic clocks have reached a frequency accuracy of few parts in 10−18, creating a potential revolution on time-frequency transfer techniques. The higher levels of accuracy and stability achievable with this technology opens a wide area to applications demanding ultra-stable frequency and timing requirements.
Optical atomic lattice clocks are a precise source for time with frequency accuracy to a few parts in 10-18. The optical frequency from these clocks needs to be disseminated over a fiber to make them fit for different applications. The paper investigates a methodology for disseminating optical frequency over a fiber by sending the operative frequency as the beat frequency of a heterodyne signal. The work details results obtained using this technique for frequency transfer over several kilometers of fiber in the lab and real environment.
In 2013, for the first time ever, a many-atom optical lattice clock surpassed single ion clocks as the most stable, and accurate frequency standard in existence. Since this first result, continued improvements to the clock's accuracy and stability have been made. This work will focus on two of these major improvements. Firstly the frequency uncertainty was brought down to 2.5*10^-18, thanks in part to an accurate determination of the black body radiation shift, based on better characterization of the level structure of 87Sr. Secondly, a control modification will be demonstrated which provides 20% reduction in the standard deviation for the clock's frequency under differential measurement schemes. This represents a new record for clock accuracy, pushing performance towards the 10^-19 level.
Atomic clocks based on laser-cooled atoms have made tremendous advances in both accuracy and stability. However, advanced clocks have not found their way into widespread use because there has been little need for such high performance in real-world/commercial applications. The drive in the commercial world favours smaller, lower-power, more robust compact atomic clocks that function well in real-world non-laboratory environments. Although the high-performance atomic frequency references are useful to test Einstein's special relativity more precisely, there are not compelling scientific arguments to expect a breakdown in special relativity. On the other hand, the dynamics of gravity, evidenced by the recent spectacular results in experimental detection of gravity waves by the LIGO Scientific Collaboration, shows dramatically that there is new physics to be seen and understood in space–time science. Those systems require strain measurements at less than or equal to 10 −20 . As we discuss here, cold atom optical frequency references are still many orders of magnitude away from the frequency stability that should be achievable with narrow-linewidth quantum transitions and large numbers of very cold atoms, and they may be able to achieve levels of phase stability, Δ Φ / Φ total ≤ 10 −20 , that could make an important impact in gravity wave science. This article is part of the themed issue ‘Quantum technology for the 21st century’.
Abstract Precision measurement and frequency metrology have pushed many scientific and technological frontiers in the field of atomic, molecular and optical physics. In this article, we provide a brief review on the recent development of optical atomic clocks, with an emphasis placed on the important inter-dependence between measurement precision and systematic effects. After presenting a general discussion on the motivation and techniques behind the development of optical lattice clocks, where the use of many atoms greatly enhances the measurement precision, we present the JILA strontium optical lattice clock as the leading system of frequency metrology with the lowest total uncertainty, and we describe other related research activities. We discuss key ingredients that have enabled the optical lattice clocks with ultracold atoms to reach the 18th digit in both precision and accuracy. Furthermore, we discuss extending the power of precision clock spectroscopy to study quantum many-body physics and to provide control for atomic quantum materials. In addition, we explore future research directions that have the potential to achieve even greater precision.