(This was my original title for my article, but my editors evidently didn’t like it. I guess I’m too old school. Ahem. Moving right along.)

As you may know, quantum physics shows that matter has both a wavelike and particle-like character. When you combine quantum physics and special relativity, you find that a particle at rest vibrates with a frequency that depends only on its mass: the Compton frequency. For most purposes, the Compton frequency is useless: it’s huge, even for low-mass particles like electrons, and scales up proportionally for more massive particles like protons. However, researchers have figured out a way to access the Compton frequency of cesium atoms by stimulating them with lasers in a particular way. This could lead to more precise atomic clocks, enabling even more detailed measurement of the second of time—and provide a new way to measure the masses of subatomic particles.

Shau-Yu Lan and colleagues exploited advanced techniques to construct an atomic clock based on a single cesium atom, a device capable of dividing the huge natural frequencies of the atom into more manageable quantities. This provided a strong demonstration of the ability to construct clocks based on a single microscopic mass. And, because we already have excellent clocks to compare them with, this can potentially work in the opposite direction, leading to accurate mass measurements in the future. [Read more…]