Editing Ytterbium (section)

===High-stability atomic clocks===
A pair of experimental atomic clocks based on ytterbium atoms at the [[National Institute of Standards and Technology|National Institute of Standards and Technology (NIST)]] has set a record for stability. NIST physicists reported the ytterbium clocks' ticks are stable to within less than two parts in 1 [[quintillion]] (1 followed by 18 zeros), roughly 10 times better than the previous best published results for other atomic clocks. The clocks would be accurate within a second for a period comparable to the age of the universe. These clocks rely on about 10,000 ytterbium atoms [[Laser cooling|laser-cooled]] to 10 microkelvin (10 millionths of a degree above [[absolute zero]]) 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 (518 THz) provokes a transition between two energy levels in the atoms. The large number of atoms is key to the clocks' high stability.<ref>NIST (2013-08-22) [https://www.nist.gov/pml/div688/clock-082213.cfm Ytterbium Atomic Clocks Set Record for Stability].</ref>

Visible light waves oscillate faster than microwaves, hence optical clocks can be more precise than [[caesium]] [[atomic clocks]]. The [[Physikalisch-Technische Bundesanstalt]] is working on several such optical clocks. The model with one single ytterbium ion caught in an [[ion trap]] is highly accurate. The optical clock based on it is exact to 17 digits after the decimal point.<ref>Peik, Ekkehard (2012-03-01). [https://www.ptb.de/cms/en/presseaktuelles/journals-magazines/ptb-news/ptb-news-ausgaben/archivederptb-news/ptb-news-2012/new-pendulum-for-the-ytterbium-clock.html New "pendulum" for the ytterbium clock]. ptb.de.</ref>