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Redefining the Second: Japan’s Staggeringly Precise Optical Lattice Clock Promises Wealth of Real-World Applications

Redefining the Second: Japan’s Staggeringly Precise Optical Lattice Clock Promises Wealth of Real-World Applications

Science<br>Technology

Jun 22, 2026

Timekeeping is an essential underpinning of daily life and a vital component of our social and technological infrastructure. The Japanese optical lattice clock, a top candidate for redefinition of the second, marks time with such staggering precision that it can measure small differences in elevation using Einstein’s theory of general relativity.

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Japan&rsquo;s strontium optical lattice clock has been called the &ldquo;ultimate timepiece.&rdquo; Developed by Katori Hidetoshi, professor of physics at the University of Tokyo and director of the Riken (Institute of Physical and Chemical Research) Spacetime Engineering Research Team, the clock boasts unprecedented precision—measured in billions of years. This amazing accuracy, capable of gauging slight differences in elevation using Einstein&rsquo;s theory of general relativity, holds immense promise as a new standard in timekeeping and a valuable tool in such fields as space exploration, earthquake research, and global positioning.

A Brief History of Time

In ancient times, human beings relied on the apparent movement of celestial objects to gauge the passage of time. The division of the day (one complete revolution of the earth) into ever smaller increments yielded the concept of the second as a tiny fraction of a day. But precision timekeeping did not develop until much later.

In the sixteenth century, the Italian astronomer Galileo Galilei (1564–1642) discovered that any pendulum of a given length would swing at a constant frequency, paving the way for the invention of the pendulum clock by the Dutch mathematician and physicist Christiaan Huygens (1629–95). (Portable spring-driven timepieces were developing around the same time.) A new era in precision timekeeping began with the development of quartz clocks, which rely on the constant frequency at which quartz crystals oscillate when exposed to an electrical charge. Some of today&rsquo;s high-accuracy quartz timepieces are accurate to within a second over 100 years.

The next major advance came in the second half of the twentieth century with the development of atomic clocks. An atomic clock keeps time using the frequency of the electromagnetic radiation absorbed or emitted when a particular atom transitions between energy states. In 1967, the cesium-133 atomic clock was adopted as the world&rsquo;s primary standard for timekeeping. As a result, one second is now defined not in relation to the earth&rsquo;s movement but as 9,192,631,770 cycles of the microwave that causes the excitation of cesium-133. The most advanced cesium devices are said to have a relative accuracy of about 1 X 10–15, which equates to a drift of just one second over 60 million years.

Dawn of the Optical Lattice Clock

The optical lattice clock is a next-generation atomic clock that makes use of visible light to achieve a mind-boggling level of precision. Visible light has a frequency several orders of magnitude higher than that of microwaves. This means many more cycles per second and thus a much more finely ruled yardstick for measuring time. The technology also uses strontium, which has a resonance frequency many times higher than cesium.

Katori first proposed his optical lattice clock in 2001. A key objective was to find a way of using a large number of atoms while avoiding the disturbances and deviations caused by interaction among those atoms. It was a problem that had stumped researchers for years.

In Katori&rsquo;s clock, the interference patterns of laser beams—tuned to a frequency dubbed the &ldquo;magic wavelength&rdquo;—create an optical lattice resembling an egg carton. Roughly a million strontium atoms, cooled to nearly absolute zero, are individually confined within this lattice. By averaging the extraordinarily high-frequency oscillations of these atoms as they absorb energy from a laser, the technology provides a dramatically more stable and precise basis for the definition of a second.

A three-dimensional model showing atoms trapped in the laser-beam &ldquo;egg crate&rdquo; of an optical lattice clock. (&copy; Jiji)

After Katori and his research team had performed a series of successful ultra-high-precision frequency measurements, their work began to attract international attention as a technology capable of playing a key role in the redefinition of the second. As early as 2006, it was designated a candidate for the next generation of precision timekeepers. However, at this stage, the optical lattice clock existed only as a massive...