The clocks, based on atoms of the element ytterbium, act like pendulums or metronomes that swing back and forth with perfect timing for a period comparable to the age of the universe, they said.
The stability of the ytterbium clocks -- measured as how precisely the duration of each "tick" matches every other tick -- creates timekeeping 10 times more accurate than any other atomic clock to date, a NIST release reported Thursday.
The ytterbium clock ticks are stable to within less than two parts in 1 quintillion (1 followed by 18 zeros), the researchers said.
"The stability of the ytterbium lattice clocks opens the door to a number of exciting practical applications of high-performance timekeeping," NIST physicist Andrew Ludlow said.
The breakthrough has the potential for significant impacts on a broad range of sensors measuring quantities that have tiny effects on the ticking rate of atomic clocks, including gravity, magnetic fields and temperature, the researchers said.
Results of the experiments have been published in the journal Science Express.