NIST sets clock to stay accurate for billions of years

Latest quantum logic clock uses aluminum ion to raise timekeeping to a new level of precision

THIS ONE GOES TO 17. How many decimal points can sit within a split second? Researchers at the National Institute of Standards and Technology take it to 17 in the process of measuring their highly accurate atomic clocks.

NIST physicists announced last month that they had built the second version of NIST’s quantum logic clock using a single aluminum ion, which is an electrically charged atom. The new clock would keep time accurately within a second for roughly 3.7 billion years, making it more than twice as precise as its predecessor, which used a mercury ion. It’s also considerably more accurate than the clock that keeps the official U.S. time, the NIST-F1 cesium fountain clock, which could lose a second every 100 million years or so. The international definition of a second is based on cesium, so for now, we’re stuck with it.

NIST said physicists measure the clocks by using the resonant laser frequency of one clock to compare against the ion in the other. The two logical clocks performed identically until the measurements were extended to 17 decimal places. We’re talking about differences in the quadrillionths — a millionth of a billionth — of 1 percent.

But this is no mere academic exercise in precision. NIST said the clocks are used to test the laws of physics and eventually could lead to new types of gravity sensors for exploring underground resources and autonomous navigation, such as landing planes via GPS.

And with March Madness starting up, we’re sure some hoop heads would just love to add 17 decimal points to the shot clock. A last-quadrillionth shot? Pandemonium, baby!

About the Author

Kevin McCaney is a former editor of Defense Systems and GCN.

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