Super-resolving frequency measurement with mode-selective quantum memory
Shicheng Zhang, Aonan Zhang, Ilse Maillette de Buy Wenniger, Paul M. Burdekin, Steven Sagona-Stophel, Anindya Rastogi, Sarah E. Thomas, Ian A. Walmsley
Published: 2025/6/25
Abstract
High-precision optical frequency measurement is indispensable to modern science and technology, yet conventional spectroscopic techniques struggle to resolve sub-linewidth spectral features. We introduce a unique platform for super-resolving frequency estimation utilizing a mode-selective atomic Raman quantum memory implemented in warm cesium vapor. By precisely engineering the light matter interaction, our memory coherently stores the optimal temporal mode with high fidelity and retrieves it on-demand, realizing a mode crosstalk as low as 0.34%. To estimate the separation between two spectral lines, we experimentally measure the mean squared error of the frequency estimate, achieving a sensitivity of 1/20 of the linewidth with a ($34\pm4$)-fold enhancement in precision over direct intensity measurements. This enhanced frequency resolution, combined with the memory's on-demand storage, retrieval, and mode conversion capabilities, paves the way for multifunctional memory-based time-frequency sensors and their integration within quantum networks.