According to a study entitled, “An Atomic Clock with 10^{−18} Instability,” which appears in an August 22 edition of the journal *Science Express*, two experimental ytterbium atomic clocks at the National Institute of Standards and Technology (NIST) have set a new record for stability. According to NIST, these clocks act as 21^{st} century metronomes, swinging to-and-fro with impeccable timing for a period (time for a single cycle) equivalent to the age of the universe.

Physicists from NIST reported in the *Science Express* article that the tick of the ytterbium atomic clocks is more stable than any other atomic clock. Stability, in this sense, can be perceived as how precisely the period of individual ticks match up. The ytterbium atomic clock ticks to a stability within less than two parts per quintillion (10^{-18}). This precision is approximately ten times better than results for other atomic clocks that were posted previously.

This remarkable advance has the potential for considerable impacts – not only on timekeeping, but also on a wide range of sensors measuring quantities that have minuscule effects on the ticking rate of atomic clocks. These quantities include gravity, magnetic fields, and temperature. In addition, the achievement is a key step in the development of next-generation atomic clocks worldwide, including at NIST and at JILA.

According to NIST physicist and co-author of the study, Andrew Ludlow, “The stability of the ytterbium lattice clocks opens the door to a number of exciting practical applications of high-performance timekeeping.”

Each ytterbium clock at NIST relies on approximately 10,000 rare-Earth atoms, cooled to 10 millionths of a degree above absolute zero, or 10 microkelvin that are trapped in a laser-optical lattice. Another laser that “ticks” 518 trillion times per second antagonizes a conversion between two energy levels in the atoms. The high stability of the clock hinges on the large number of atoms used. Due to this high level of constancy, the ytterbium clocks can make measurements extremely quickly, which could be important in rapidly changing such application settings as the factory floor and the natural environment.

A key advance that enabled the landmark performance of the ytterbium atomic clocks was the latest production of a ytterbium atomic clock to calculate and progress the performance of the original, which has been developed since 2003. Spanning from that time to the present, NIST scientists have made several modifications to both atomic clocks, including the expansion of an ultra-low-noise laser used to excite the atoms, and the discovery of a method to cancel disruptive effects caused by collisions between atoms.