A pair of experimental atomic clocks based on ytterbium atoms at NIST has set a record for stability. Acting like 21st-century pendulums, the clocks have perfect timing and could potentially swing back and forth with precise ticks for a period comparable to the age of the universe. The tick of the ytterbium clocks is more stable than that of any other atomic clock, with each tick matching every other tick to within less than two parts in one quintillion (10−18), NIST physicists have reported. That’s roughly 10 times more accurate than in previously published reports. In the ultrastable ytterbium lattice atomic clock, ytterbium atoms are generated in an oven (large metal cylinder on the left) and sent to the vacuum chamber (in the center of the photo) to be manipulated and probed by lasers. Laser light is transported to the clock by five fibers (such as the yellow fiber in the lower center of the photo). Photo courtesy of Burrus, NIST. This breakthrough has the potential for significant impacts not only on timekeeping, but also on a broad range of sensors, including those that measure gravity, magnetic fields and temperature. This accuracy is also a major step in the evolution of next-generation atomic clocks. “The stability of the ytterbium lattice clocks opens the door to a number of exciting practical applications of high-performance timekeeping,” said NIST physicist Andrew Ludlow. Each of NIST’s ytterbium clocks relies on 10,000 rare-earth atoms cooled to 10 µK and trapped in an optical lattice – a series of pancake-shaped wells made of laser light. Another laser that “ticks” 518 trillion times per second provokes a transition between two energy levels in the atoms. The ytterbium clocks can make measurements extremely rapidly – in real time, in many cases – which could be important in fast-changing application environments, such as factory floors or the natural environment. A key advance in the development of ytterbium clocks was the recent construction of a second version of the clock to measure and improve the performance of the original, developed since 2003. Along the way, NIST scientists have made several improvements to both clocks, including the development of an ultralow-noise laser to excite the atoms, and the ability to cancel disruptive effects caused by atom collisions. The research was published in Science (doi: 10.1126/science.1240420).