Racing to shrink time into the world's smallest atomic clocks

DARPA's stringent requirement demands these clocks to maintain accuracy within a millionth of a second after a week.

Macro to Micro.

The concept of atomic clocks traces back to 1948 when it was first developed at what is now the National Institute of Standards and Technology. 

Unlike traditional timekeeping mechanisms relying on celestial or mechanical events, atomic clocks leverage electromagnetic signals emitted by atoms, resulting in unparalleled precision. These clocks play an instrumental role in Global Positioning System (GPS) technology, ensuring accurate and synchronized navigation.

Ironically, DARPA, which initially supported GPS advancement, is now investigating small, accurate clocks to navigate when GPS signals are absent. 

Precise navigation hinges on reliable timekeeping and is akin to calculating distance on a highway ride. For military applications, pinpoint accuracy is imperative. 

DARPA's pursuit aims to achieve 30 times the accuracy of existing small-scale clocks while optimizing power consumption and sensitivity to external factors like temperature and vibration.

"This is way more challenging than what people have done so far," acknowledges Yuan-Yu, highlighting the magnitude of the task.

Engineering Precision from Past to Present.

Yuan-Yu's confidence in his team's ability to construct these minuscule marvels stems from a prototype he crafted 16 years ago during his tenure at Princeton University. 

The prototype, resembling a toolbox in size, operated like an atomic clock, generating a steady pulse by passing a laser through a cloud of potassium atoms. Notably, this early design was self-contained, eliminating the need for external electronic components to manage the clock's periodic pulse.

Yuan-Yu points to his “sausage fingers” when speaking about his prototype being not as small as possible.

Yuan-Yu's current endeavor capitalizes on his experience, aiming to refine his prototype using Sandia's cutting-edge Microsystems Engineering, Science and Applications complex. 

Sandia helped develop the Chip Scale Atomic Clock (CSAC), about 17 cubic centimeters, in the early 2000s. The CSAC is still the smallest clock available to purchase.

Armed with the tools to make the clock smaller, he anticipates significant reductions in size, weight, and power requirements by eliminating unnecessary peripheral hardware.

“We will use only the volume of the physics package that exists in the existing CSAC clock, but we will get rid of those complicated electronics around it,“ Yuan-Yu said.

As Yuan-Yu embarks on this ambitious mission, his project has secured initial funding from DARPA for two years, with the potential for extended support upon meeting size and performance benchmarks.