Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Standards of time and frequency at the outset of the 21st century

Published

Author(s)

Scott Diddams, James C. Bergquist, Steven R. Jefferts, Christopher W. Oates

Abstract

In this paper we review state-of-the-art atomic time and frequency standards and discuss some of their uses in science and technology. After fifty years of development, microwave atomic clocks based on cesium have achieved fractional uncertainties below 1 part in 1015; a level unequaled in all of metrology. The past five years have seen accelerated development of optical atomic clocks, which hold significant potential for still improved timekeeping. Time and frequency standards with various levels of performance are ubiquitous in our modern society, finding applications in many technological fields as well as in the continued exploration of the frontiers of basic science.
Citation
Science
Volume
306

Keywords

atomic clock, microwave and optical frequency standards, time standards

Citation

Diddams, S. , Bergquist, J. , Jefferts, S. and Oates, C. (2004), Standards of time and frequency at the outset of the 21st century, Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=50063 (Accessed March 29, 2024)
Created November 18, 2004, Updated October 12, 2021