Synchronizing satellites with frequency combs

Today there are some 10,000 active satellites encircling Earth — a number that is rapidly increasing. In this space-faring era, optical clock synchronization between satellites is becoming increasingly important for network speed and function. Frequency combs, which offer synchronization at and beyond the standard quantum limit, are perhaps one of the most promising ways to achieve this.

Gosalia et al. analyzed classical and quantum frequency combs, which together could form the backbone for optical clock synchronization all the way to Mars and beyond. The authors discussed what can be achieved with classical frequency combs and what advantages quantum versions might offer. They also covered the challenges of using frequency combs in space as well as their future prospects.

“A highly synchronized network of optical clocks will have applications in almost every field of technology,” said author Ronakraj Gosalia. “The most important, from our perspective, are communications, both classical and quantum, navigation using enhanced-GPS with sub-millimeter accuracy, and sensing.”

The researchers aim to provide insight for future studies as well as help others understand the challenges of and advantages to using frequency combs for synchronization. Many research endeavors may also benefit, including gravitational wave detection, dark-matter searches, tests of time-variations in fundamental constants, foundational tests of quantum mechanics, and new physics at the quantum-gravity interface.

“We are most excited to see the classical and quantum frequency comb field move toward generation and detection devices that are low size, weight, power, and cost,” Gosalia said. “Integrated photonics may play a key role in this field, and global efforts are already underway.”

Source: “Classical and quantum frequency combs for satellite-based clock synchronization,” by Ronakraj K. Gosalia, Ryan Aguinaldo, Jonathan Green, Holly Leopardi, Peter Brereton, and Robert Malaney, APL Photonics (2024). The article can be accessed at https://doi.org/10.1063/5.0220546 .