Time and Frequency Division

The Time and Frequency Division, part of the NIST Physical Measurement Laboratory, maintains the standard for frequency and time interval for the United States, provides official time to the United States, and carries out a broad program of research and service activities in time and frequency metrology.

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NIST's Second "Quantum Logic Clock" is World's Most Precise Clock

NIST scientists have built a second "quantum logic clock," using quantum information processing techniques on a single ion of aluminum to make a clock that would not gain or lose more than one second in about 3.7 billion years.  

For more information, please see http://www.nist.gov/pml/div688/logicclock_020410.cfm.