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Amar Vutha (Fellow 2014–19)

What characterizes Amar Vutha’s approach is the courage to think outside the box. Why not make an atomic clock that’s a thousand times more precise than any existing one – and portable to boot? This was his premise when he applied for a Branco Weiss Fellowship in 2014. Six years later he’s still doing experimental atomic physics in pursuit of his original idea, but he hasn’t been able to resist venturing into new fields as well.

FoF Amar Vutha

Amar Vutha managed to get three projects out of one fellowship.

“When I applied in 2014 there was no fellow in physics,” says Amar Vutha. “What’s more, it was highly questionable why anybody should fund my proposed research, since there was virtually no way to argue that it had any societal benefits in the generally accepted sense.” Today’s atomic clocks employ lasers to cool and slow down atoms from the gas phase in a vacuum to near absolute zero temperature. This requires a large-scale device in each country to provide the national primary time and frequency standards. These include the NIST-F1 atomic clock in the United States and the PTB cesium atomic clock in Germany. These devices are all synchronized with each other and have an uncertainty of one second in 30 million years. This degree of accuracy is required to operate global navigation satellite systems such as GPS, which nowadays are precise to about one meter. But the new generation atomic clocks operate at optical frequencies and are even more accurate. Taking advantage of the revolutionary changes in optical frequency measurement techniques that had occurred a few years prior, Amar suggested producing a portable optical atomic clock.

While Amar was working on building such a clock, in conversation with colleagues at the Canadian national metrology lab he learned that their atomic clock produced small errors induced by sudden “bumps” of the atom caused by background gas molecules. Amar, who considers himself an experimentalist, acted out of character and set about constructing a new theoretical framework to understand quantum information transfer in atomic collisions. He calculated that the effect of these bumps on the clock is 100 times smaller than previously thought. The next step was to develop a refined method for estimating the effect of these collision-induced errors, and thus provide a framework that “anyone can use now,” as he puts it.

Amar argues that his next idea can be wholly attributed to the freedom provided by the Branco Weiss Fellowship, since it falls way outside established approaches. He goes as far as to call the idea heretical: Why not bypass the trapping lasers by using an atom that’s already fixed by virtue of being part of a crystal structure? He found the most suitable atomic structure in an obscure rare-earth metal called samarium. The idea works, and even has the potential to be a game-changer for atomic clocks. Cumbersome vacuum systems and multiple trapping lasers may no longer be necessary! Thanks to the freedom and flexibility of the Branco Weiss Fellowship, Amar was able to devote two years of research to this idea, and his team found the longest-lived optical transition in a solid-state system. In due course, atomic clocks are likely to become much smaller and cheaper – and a thousand times more accurate. This could improve the precision of GPS systems. What’s more, an atomic clock of this sort could be placed by itself on a satellite, to provide its signal all across the globe or be used for measurements in fundamental physics.

Even when Amar conducts a mundane experiment it’s anything but down to earth. On the contrary: a few years before gravitational waves were first observed, Amar had realized that these could be detected using atomic clocks based on satellites. During the final year of his fellowship, his team built two atomic clocks and operated them on a high-altitude balloon. His idea was to prove that they could operate remotely for over 10 hours at an altitude of 40 kilometers above the earth’s surface, despite huge variations in temperature, humidity, and air pressure.

“I managed to get three projects out of one fellowship,” says Amar. “In basic research, we need the freedom to sometimes try out new things! The Branco Weiss Fellowship has made me bolder in my approaches.” Amar also emphasizes the importance of meeting the other fellows during the annual symposia. Many of these fellows are fueled by a sense of wonder and excitement that one does not often come across in science – but when it does occur, it is truly magical.