Dr. David Wineland, National Institute of Standards and Technology
Abstract
Atoms absorb electromagnetic radiation at certain precise frequencies. Knowing this, a recipe for making an atomic clock is fairly simple to state: we first need an oscillator to produce radiation and a device that tells us when the atoms absorb it, thereby indicating that the oscillator frequency is synchronized with the atoms’ absorption frequency. To make a clock from this apparatus, we then simply count cycles of the oscillator – the duration of a certain number of cycles defines a unit of time, for example, the second. In one of the world’s most accurate clocks, we count the cycles of an oscillator that has a frequency of 1,052,871,833,148,990.44 cycles per second – corresponding to a near-ultraviolet absorption frequency in 27Al+ ions. At this level of precision, many effects, including those due to special and general relativity, can affect our measurements; therefore, our primary task is to determine and correct for these perturbing effects. For many centuries and still continuing today, a primary application of accurate clocks is for precise navigation.
Small reception will follow in the EIT foyer.