Synchronize watches: NOW!

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  • Published: Feb 15, 2015
  • Author: David Bradley
  • Channels: Atomic
thumbnail image: Synchronize watches: NOW!

Cryo time

Cryogenically cooled optical lattice clocks can be synchronized to one part in 2.0 x 10^18, which means they will differ by just one second every 16 billion years or so. This is a thousand times more precise than current state of the art caesium atomic clocks and could have implications for instrumentation used in the measurement of fundamental physical constants.

Cryogenically cooled optical lattice clocks can be synchronized to one part in 2.0 x 10^18, which means they will differ by just one second every 16 billion years or so. This is a hundred times more precise than current state of the art caesium atomic clocks and could have implications for instrumentation used in the measurement of fundamental physical constants.

When the plan is in place, the scheming all plotted, the protagonists in that "B movie" will all synchronize their watches and set off on their adventure. Now, in work supported by the Katori Innovative Space-Time Project of the Japan Science and Technology Agency's ERATO program, researchers have taken the idea of synchronisation into a whole new epoch. Hidetoshi Katori, of RIKEN's Quantum Metrology Laboratory and the University of Tokyo's Graduate School of Engineering and colleagues have demonstrated that they can synchronise their "watches" to a precision far greater than the age of the universe, to an accuracy that would waver by a mere second in 16 billion years.

Non-standard deviation

The team of Katori and colleagues Ichiro Ushijima, Masao Takamoto, Manoj Das and Takuya Ohkubo, describes details of their hyper-precise, cryogenically cooled optical lattice clocks in the journal Nature Photonics. They point out that this level of precision is almost one thousand times more precise than the current international timekeeping standard, the caesium atomic clock, with its 10-15 uncertainty.

Of course, there are no best laid plans in any "B movie" that need such a degree of precision. However, this development could represent a turning point for clock-based geodesy and other applications. Relativistic geodesy has been mooted as an interesting way of determining the shape of our planet using a satellite with a highly accurate clock on-board the "tick-tocking" of which would change with variations in the Earth's gravitational field. The tiny differences would be exposed only over the course of millions of years unless one had an astoundingly accurate timekeeper, which is where the cryo clock should come into play.

The team's optical lattice clock will allow us to take measurements of how different parts of the earth are moving, upward or downward, relative to each other, and thus could contribute to a better understanding of geological processes such as those that lead to earthquakes.

I got a feeling

Katori's team built their system by trapping strontium atoms in a laser-generated optical lattice with a "magic" wavelength. At this wavelength, the light holds the atoms but otherwise does not affect their properties, at least at minus 180 Celsius, the temperature at which blackbody radiation is also eliminated. The team observed the electronic transition frequencies of two such clocks over a period of one month.

"It was a great feeling to have shown this excellent agreement between the clocks," Katori enthuses. "If we can miniaturize this technology further, it would have useful applications, since tiny fluctuations in gravitational potential could be used to detect underground resources, underground spaces, and the movement of lava. We also hope that in the future, this will accelerate the movement toward a new definition of the international second, based on optical lattice clocks, to an even more stringent standard than the current definition of the second, which is based on caesium oscillation."

"We hope to push optical lattice clocks' uncertainty to 10-19 level," Katori told SpectroscopyNOW.

Related Links

Nature Photonics, 2015, online: "Cryogenic optical lattice clocks"

Article by David Bradley

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.

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