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Cold atom optical clocks: keeping time to 17 digits

Nathan Lemke, PhD, Physics Division, Argonne National Laboratory

Tuesday, October 1, at 3:45 p.m. in SB110.

Since 1967, the SI unit second has been defined by the oscillation frequency between the two lowest energy states of the cesium atom, at a frequency near 9.2 GHz. Worldwide atomic time is maintained by an ensemble of earth- and space-based cesium clocks, capable of measuring time to better than 1 part in 1015 and enabling many important applications such as the global positioning system. With the advent of the optical frequency comb around the year 2000, optical atomic clocks (with oscillation frequencies of a few hundred THz) have rapidly developed to become even more accurate and precise than their microwave predecessors. Today, an international effort is underway to evaluate many different types of optical clocks to see which should ultimately become the new primary standard for time and frequency, with a goal of reaching an inaccuracy below 1 part in 1018. In this talk, I will describe the design and operation of these cold atom optical clocks, with brief descriptions of the various systems competing to become the new primary standard. I will also mention a few of the applications that could benefit from such exquisite control of time and frequency.





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