Atomic Clock

An atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, and to control the frequency of television broadcasts and GPS systems.

In August 2004, NIST scientists demonstrated a chip-scaled atomic clock.^[8] According to the researchers, the clock was believed to be one-hundredth the size of any other. It was also claimed that it requires just 75 mW, making it suitable for battery-driven applications. This device could conceivably become a consumer product.

In March 2008, physicists at NIST demonstrated optical atomic clocks based on individual mercury and aluminum ions. These two clocks are the most accurate that have been constructed to date, with neither clock gaining nor losing at a rate that would exceed a second in over a billion years.