A radium-225 ion optical clock
Abstract
Approved for Public ReleaseProject AbstractReliable, high precision, portable timekeeping is at the heart of navigation. Optical clocksare promising for navigation as they are the world#s 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 ion trapping mechanism. We will develop a new optical clock basedon the radium-225 ion that addresses the need to reduce clock size, weight, and power.This atomcombines 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 realizing the first radium-225 ion optical clock. We will make the firstmeasurements of key properties to evaluateclock operation, including a polarizabilitythat will help reduce the effects of black body radiation, micromotion, and Doppler shifts.We will make the first measurement of the clock state#s electric quadrupole moment, animportant quantity for characterizing an optical clock, and of particular importance fordesigning an optical clock based on multiple ions which opens the door to improvingshort-term clock stability. We will operate a radium-225 ion clock and evaluate its stabilityby comparing it with a second radium optical clock. The atomic source has very lowradioactivity, and through this research effort we expect that the already low activity canbefurther 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 realizing an optical clock with this nuclear spin zeroisotope. Recently we laser cooled radium-225 and made important measurements of itshyperfine structure. The next step is making an optical clock with radium-225 and characterizingsystematic uncertainties. This isotope has desirable nuclear structure that forsubstantially reduces sensitivity to magnetic field noise, a key limit to achieving longcoherence times. The other properties of this atom make it promising not only for transportableoptical clocks but also for realizing very high precision clocks.We will adapt techniques and approaches from successful clock research with otherion species, such as strontium and ytterbium. The critical atomic properties we will measurehave been previously measured in other species, which will accelerate our proposedradium work.We expect the appealing features of radium will significantly ease barriers towardsrealizing practical optical clocks. Our work will mark 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
- Feb 24, 2025
- Source ID
- N000142512131
Entities
People
- A. M. Jayich
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara