Three of the world’s leading measurement laboratories, including the U.S. Commerce Department’s National Institute of Standards and Technology’ have lined up the hash marks from four of the world’s best optical frequency rulers and declared that they match.

The experiments, reported in the March 19 issue of the journal Science 1, are a significant step toward next-generation atomic clocks based on optical rather than microwave frequencies. Such clocks are expected to be as much as 100 times more accurate than today’s best timekeeping systems.

Although the new technology won’t affect average wristwatch wearers, it will provide the ultra-precise timekeeping necessary for navigation, telecommunications and basic scientific research.

Optical rulers are lasers that emit pulses of light lasting 10 femtoseconds (10 quadrillionths of a second, or 10 millionths of a billionth of a second). The experiments demonstrated that femtosecond laser devices could be used to reproducibly generate and accurately control the frequency of electromagnetic fields, a critical step in taking the measurement of time beyond its current accuracy level of about 0.1 nanosecond per day (i.e., losing or gaining no more than about 0.1 billionths of a second per day).

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