High-Accuracy Quantum-Logic Clocks based on Highly Charged Ions
Abstract
Several highly charged ions (HCIs) possess narrow linewidth clock transitions that are ideal for the development of high-accuracy optical atomic clocks. The 338.8 THz (884.9 nm) electric quadrupoletransition between the ground and first excited electronic states in quadruply-ionized barium (BaV) has several features that make it a particularly promising candidate for a high-accuracy optical atomic clock. The lifetime of the excited clock state is 8.3 s, accommodating low statistical uncertainty with a single ion for practical averaging times. The differential static scalar polarizability is extremely small, providing suppressed sensitivity to the blackbody radiation (BBR) shift. The charge-to-mass ratio of BaV is well suited to sympathetic cooling and quantum-logic readout using aco-trapped calcium ion (CaII), which is an excellent clock ion. In addition, the low ionization energy of approximately 60 eV makesBaV a great candidate for production using a compact ion source. Here, I propose the continued development of a quantum-logic clockbased on BaV and describe the advantages of this system as well as the experimental apparatus needed to realize this novel optical clock. In addition, the apparatus and techniques used for this BaV clock could also be used for the development of other HCI-based optical clocks. Over the past two decades, significant progress has been made in the development of atomic clocks based on optical transitions. State-of-the-art optical atomic clocks interrogate either an ensemble of neutral atoms confined in an optical lattice, oran individual ion confined in a Paul trap. Ion clocks demonstrated thus far tend to employ singly charged ions, however, several laser-accessible transitions in HCIs have been identified which possess both a high quality factor and insensitivity to environmental perturbations, making them potential candidates for new optical atomic clocks. Recent theoretical work suggests that optical clocks based on fine structure transitions in HCIs that could realize fractional systematic uncertainties below one part in ten to the twenty. However, the relatively short excited state lifetimes of these systems present a major challenge in developing a clock that willpossess both low systematic uncertainty (accuracy) and low statistical uncertainty (frequency instability). To address these and other limitations in previous proposals, I present BaV as an exciting new direction for the development of a high accuracy quantum-logic clock. Considering all known systematic shifts, the total fractional systematic uncertainty for this clock has been estimated to be one part in ten to the nineteen, or below. BaV has several features which make it an attractive candidate for a new quantum-logicclock. These include, (i) a clock transition with a low sensitivity to blackbody radiation, (ii) a charge-to-mass ratio which is well matched to sympathetic cooling and quantum-logic operations using a co-trapped calcium ion, and (iii) a clock transition wavelength of 884.9 nm which is easily addressed using commercial solid-state lasers. In addition, many systematic shifts can be characterized using the co-trapped CaII ion which will allow for important benchmarks for the ultimate clock performance that can be achieved. The future naval relevance of this work is related to precise timekeeping requirements needed for future improvements to naval navigation. The work proposed here aims to address several performance accuracy and instability) limitations that exist in previously demonstrated optical clocks. This new clock could lead to the development of improved time and frequency standards for use in various naval applications.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 13, 2025
- Source ID
- N000142512094
Entities
People
- Samuel Brewer
Organizations
- Colorado State University
- Office of Naval Research
- United States Navy