Developing an optical clock featuring immunity to noise and compatibility with integrated photonics
Abstract
Reliable, high precision, portable timekeeping is at the heart of navigation. Optical clocksare promising for navigation as they are the worlds best chronometers. But, portableoptical clocks, that are required for navigation, are in their infancy, with many advancesneeded in key metrics, especially system reliability and size. Trapped ion optical clocksare a promising solution because of their small size, well understood systematic shifts,and the robust trapping mechanism. We will develop a new optical clock based onthe radium-225 ion that addresses the need to reduce an clock size, weight, and power.This atom combines a host of desirable atomic properties, including wavelengths that arehighly compatible with integrated photonics, and a nuclear spin that makes the ion bothstraightforward to manipulate and highly insensitive to magnetic field noise, a key sourceof decoherence.We propose to trap and laser cool the radium-225 ion. With trapped radium-225 ionswe will be able to make the first measurements of key properties to evaluate clock operation, including differential polarizabilities that will help us understand the effects of blackbody radiation and micromotion. We will resolve a long-standing discrepancy betweentwo measurements of the ions grounds state structure. We will make the first measurement of the clock states electric quadrupole moment, an important quantity for characterizing an optical clock, and of particular importance for designing an optical clock basedon multiple ions which opens the door to improving short-term clock stability. We willoperate a radium-225 ion clock and evaluate its stability by comparing it with a secondradium optical clock. The atomic source for the ions will be based on the natural decayof thorium to radium, which will provide a continuous supply of radium atoms for theclock. The atomic source will have very low radioactivity, and through this research effortwe expect that the already low activity can be further reduced.Our lab has extensive experience working with radium ions. We were the first groupto laser cool the radium ion and have since performed many first measurements of thesystem with radium-226, including measurements that are important for the proposedoptical clock. The next step is working with radium-225, which has the desirable nuclear structure for substantially reducing sensitivity to magnetic field noise, a key limit toachieving long coherence times.We will adapt techniques and approaches from successful clock research with otherion species, such as strontium and ytterbium. The critical atomic properties that we willmeasure have been previously measured in other ion species, which will accelerate ourproposed work with radium.We expect the appealing features of radium will significantly ease barriers towardsrealizing practical optical clocks. Our work will realize a significant advance: establishinga radium-225 ion optical clock, opening the door to a robust portable clock.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 05, 2021
- Source ID
- N000142112597
Entities
People
- A. M. Jayich
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara