Probing, Quantifying and Freezing Coherence in a Thermal Ensemble of Atoms

TL;DR

This paper introduces a new quantifier for measuring and controlling quantum coherence in room-temperature atomic ensembles, demonstrating the transition from EIT to ATS and coherence freezing.

Contribution

It proposes an experimental method to quantify and actively control coherence in thermal atomic ensembles, advancing room-temperature quantum system research.

Findings

New coherence quantifier for atomic ensembles

Demonstration of coherence control and freezing

Observation of EIT to ATS transition

Abstract

Creating stable superposed states of matter is one of the most intriguing aspects of quantum physics, leading to a variety of counter-intuitive scenarios along with a possibility of restructuring the way we understand, process and communicate information. Accordingly, there has been a major research thrust in understanding and quantifying such coherent superposed states. Here we propose and experimentally explore a quantifier that captures effective coherent superposition of states in an atomic ensemble at room-temperature. The quantifier provides a direct measure of ground state coherence for electromagnetically induced transparency (EIT) along with distinct signature of transition from EIT to Autler-Townes splitting (ATS) regime in the ensemble. Using the quantifier as an indicator, we further demonstrate a mechanism to coherently control and freeze coherence by introducing an active decay compensation channel. In the growing pursuit of quantum systems at room-temperature, our results provide a unique way to phenomenologically quantify and coherently control coherence in atom-like systems.