Super-resolving frequency measurement with mode-selective quantum memory

TL;DR

This paper demonstrates a quantum memory-based method for super-resolving optical frequency measurements, significantly surpassing traditional techniques in precision and enabling advanced quantum sensing applications.

Contribution

It introduces a mode-selective atomic Raman quantum memory platform that enhances frequency resolution beyond the linewidth limit with high fidelity and low crosstalk.

Findings

Achieved a sensitivity of 1/20 of the spectral linewidth.

Realized a 34-fold improvement in frequency measurement precision.

Demonstrated on-demand storage and retrieval of spectral information.

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.