WHAT: Optical Atomic Clock
WHERE: National Institute of Standards and Technology, Boulder, Colorado
WHO: NIST Time and Frequency Division
WHY: Since the creation of the first atomic clock in 1949, NIST researchers have been developing ever-more-accurate timepieces. The optical clock signals a paradigm shift: It measures time using the femtosecond - one-quadrillionth of a second - making it potentially 1,000 times more precise than today's time leader. Future communications networks, laboratory instruments, and advanced GPS receivers all depend on the most exacting synchronization. But the prototype won't reach industry for decades.
HOW: Like previous atomic clocks, this new device derives its accuracy from locking the "swing" of its laser "pendulum" to the oscillations of an atom (in this case a mercury ion), which - when excited - shifts between two quantum-mechanical energy levels. Since the oscillations are largely unaffected by temperature, pressure, or humidity, they provide a stable and standard unit of measurement. The pulse of the ion-locked laser is detected by a second laser, which "ticks" once for every 532,361 swings of the pendulum - or about once a nanosecond. That's slow enough to be measured by a photodiode and translated by standard electronics into seconds, minutes, and hours.
