Clocks measure time by counting the number of vibrations of an oscillator which vibrates regularly at uniform intervals.
“Optical lattice clock”, traps atoms in an optical lattice formed by a standing wave on a scale shorter than the wavelength of the trapping lasers (about tens of nanometers), ticks the optical frequency which comes from the trapped atoms.
The optical lattice clock was originally proposed by Professor Katori in 2001 and first demonstrated by his laboratory at the University of Tokyo in 2003. The clocks are currently being developed all over the world and provide 18 digits of time measurement accuracy (corresponding to an error of one second in 30 billion years).
Optical lattice clock is one of the promising candidates for the new definition of the second. Such a high-precision clock holds potential for new roles. It is possible to investigate the constancy of physical constants comparing two clocks consisted of different atomic elements. Furthermore, two clocks at different heights detect the relativistic space-time distortion induced by gravity due to the Einstein’s general relativity. Now, the role of such clocks is changing from a mere tool to share the time to advanced fields like investigating for new physics and exploring relativistic geodesy or chronometric levelling.

Optical Lattice Clock
2015
Size: 800×800×800
Production: Professor Hidetoshi Katori, Department of Applied Physics, School of Engineering, The University of Tokyo
Collection: Department of Applied Physics, School of Engineering, The University of Tokyo
An optical lattice clock, which is a kind of optical atomic clocks, employs atoms trapped in an optical lattice formed by a standing wave of light. The optical lattice clock improves the cesium clocks, which is used to define the SI second, by nearly two orders of magnitude. In other words, the clock loses less than a second in 30 billion years.