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Looking for the exact time? Here it is

Artistic rendering of optical lattice clocks. They could help researchers detect the ripples in space-time known as gravitational waves, among many potential applications. Image credit: C. Henze/NASA Ames Research Center

Looking and creating tools to measure time has been a thousands years long endeavour. From water and sand “clocks” to ever more sophisticated sundials our ancestors did their best. Interestingly the quest was steered in the Western World by “business” reasons, whist in the Eastern World it was rooted, as it used to be in the ancient times, by the need to follow the stars (and the gods that might have been hiding among them). This difference was reflected in the culture of people and their perception of time. As reported in the Songlines, by Bruce Chatwin, an Australian aboriginal told him: “you have the watch, we have the time”. I have to say I experienced several time this difference in the perception of time in my travels in Africa and South East Asia (far away from urban areas).

The age of exploration in the XV century gave further impulse to find a way to measure, in a reliable way, and on a moving ship, the time because this was essential to find out your location in the middle of nowhere (latitude is not tricky, longitude without a reliable clock is close to impossible to determine with a useful precision).

Today we live in a world where the measure of time in our everyday life is no longer an issue. Our smartphone can provide a time that is “exact” for any practical purpose we might have. Indeed, time measurement has become so precise that it is now several decades that we are no longer seeing ads of watches making of their precision a selling point. We take precision for granted and even the cheapest watch is precise beyond our needs.

If we were to look “inside” out smartphone, however, we would discover that precision has grown to a point that goes way further our perceived needs, into the sub-millisecond space. This is required for the GPS chip – watch the clip- inside the phone to calculate the our location (this is done by measuring the time difference of signals arriving from several satellites, this difference is so tiny, and their relative speed so high, that the chip has to take into account the special relativity formula for measuring time among moving reference frames).

Of course a difference of some 20 metres may not be that important as you walk around but that can make a difference if you are landing a plane … (today’s plane are using a mix of GPS and local landing aids, ILS).

In elementary particle physics, time precision is considered at a completely different scale. Atomic clocks, based on the vibration of a cesium atom (actually, 1 second is defined as the time it takes the radiation, that result in an electron quantum leap in a cesium atom, to make 9,192,631,770 cycles) deliver a precision of 1 second over a 100 million years, in other words, you can rest assured that after a hundred million years that clock could be “wrong” of plus or minus one sec, max. I would say that is a pretty precise clock!

Yet, in their quest for ever more precise clocks scientists have announced a new “clock” based on a different technology, optical lattice, that push the precision to better than 1 second over 30 billion years, double the life time of the universe estimated from the Big Bang. That’s amazing but of course the question is: what can I do with such a clock that would not be possible with the -now low precision- atomic clock? Well, it turns out that such (1,000 times) increased precision comes handy when physicists wants to observe gravitational waves, when they want to make more accurate tests of the general relativity theory and even in the prediction of earthquakes by measuring tiny changes in the local Earth gravity. Closer home, optical lattice clocks can improve the accuracy of GPS and this can help making autonomous cars safer (and cheaper).

The optical lattice clocks leverage on the property of laser light beams creating a web that can trap atoms, in this case strontium atoms, and keep them suspended in a sort of void so that their vibration can be measured accurately, resulting in the type of precision stated above. In the figure an image the rendering of this optical web trapping two atoms.

The optical lattice clock “invention” brought their inventors, Hidetoshi Yatori and Jun Ye, the 2022 Breakthrough Price (the other two prices were awarded to the inventors of the technology that brought us the mRNA Covid vaccine, and to the theory of bundles in mathematics) announced on Sept. 9th, 2021.

About Roberto Saracco

Roberto Saracco fell in love with technology and its implications long time ago. His background is in math and computer science. Until April 2017 he led the EIT Digital Italian Node and then was head of the Industrial Doctoral School of EIT Digital up to September 2018. Previously, up to December 2011 he was the Director of the Telecom Italia Future Centre in Venice, looking at the interplay of technology evolution, economics and society. At the turn of the century he led a World Bank-Infodev project to stimulate entrepreneurship in Latin America. He is a senior member of IEEE where he leads the Industry Advisory Board within the Future Directions Committee and co-chairs the Digital Reality Initiative. He teaches a Master course on Technology Forecasting and Market impact at the University of Trento. He has published over 100 papers in journals and magazines and 14 books.