NSF-NSERC: Applications of Quantum Frequency Comb Interferometry

The optical frequency comb is one of the most significant advances in laser science since the development of the laser itself—driving advances in precision timing, spectroscopy, attosecond science, and astronomy. While interferometry with frequency combs is adjacent to multiple quantum systems, such as the best clocks and advanced molecular sensors, in the vast majority of these applications optical frequency combs operate as purely classical laser sources. As a result, the precision of present frequency comb interferometric measurements is limited in achievable signal-to-noise ratio by shot-noise and the standard quantum limit. In this research project, we will introduce squeezed frequency comb sources to interferometry measurements in cases where it is challenging to find other classical improvements. This will allow us to push the sensitivity and practicality of quantum frequency comb interferometry beyond existing noise limits. The positive outcome of this research could lead to improved spectroscopic sensors for applications in safety and security, health screening, drug development, food production chains, and navigation. In this proposal, we aim to realize and extend quantum advantages in interferometry with single and dual frequency combs along three interlocking themes: (1) Studying new realizations of quantum interferometry for Fourier transform spectroscopy, (2) Realizing quantum enhancement in dual-comb based optical time transfer experiments with phase-squeezed combs, and (3) Extending the bandwidth and range of new frequency comb sources to provide squeezed comb light in previously inaccessible wavelength regions. These advances will have particularly significant impact because frequency-comb-based spectroscopy and time transfer are two fields where we already find ourselves at the shot noise limit, with little or no straightforward option to increase the optical power. Our strategies for quantum gain will thus lead to faster and better measurements in laboratory spectroscopy and remote sensing. In addition, this research should impact two-way optical clock synchronization with pairs of frequency combs that will form the backbone for future optical clock networks for fundamental scientific studies and the most advanced navigation systems. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.