Scientists devise simplest clock yet from single atom

Scientists claim to have developed the simplest clock yet, based on just a single atom. The new device to measure time could also help lead to a radically new way to define mass as well, scientists said. This achievement suggests that researchers might one day build even more exotic clocks - ones based on anti-matter, or ones based on no particles at all, LiveScience reported.

Fundamentally, all clocks measure time by relying on parts that repeat behaviour in regular patterns. For instance, a year is defined by how long it takes for Earth to complete an orbit around the Sun.
The most accurate clocks that currently exist are atomic clocks. These depend on how atoms switch between two distinct energy levels. Essentially, these clocks rely on at least two particles - the nucleus of an atom, and an electron leaping back and forth between different levels of energy.
"We were interested in what the simplest clocks are to explore the question of what time is," said researcher Holger Muller, from the University of California at Berkeley. "If you say that, say, you can't measure time with less than two particles, does that mean that anything below two particles doesn't experience time at all?" said Muller.
Researchers theorised it was possible to create a clock made up of just one particle. To understand, they started with Einstein's famous equation E=mc2, which shows that matter can be converted to energy and vice versa. One consequence of this, defined as de Broglie's matter-wave hypothesis, suggests that matter can also behave like waves. Which means a particle of matter can in principle behave like a wave that oscillates in a regular manner, thus acting like a clock.
"We've shown that one single particle really can measure time," Muller said. The problem with making a clock from a particle of matter is that the frequency at which it oscillates "should be so high that one should never be able to measure it," Muller said.
To overcome the hurdle, scientists relied on a phenomenon known as time dilation, another consequence of Einstein's theory of relativity. This suggests that as objects move away from and back to a location, they experience less elapsed time than objects that stayed at that location the entire time.
Researchers recreated this phenomenon using lasers on cesium atoms, the report said. "We essentially split an atom into two halves, and had one stay where it is and the other go forward and come back. A tiny, tiny bit less time elapsed for the half that moved, so it oscillated less," said Muller.